• Distorted Sine Wave

    From Cursitor Doom@21:1/5 to All on Wed May 29 17:07:25 2024
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I was building and in the process of trying to iron out the wrinkles of and
    certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Arie de Muijnck@21:1/5 to Cursitor Doom on Wed May 29 21:43:54 2024
    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I was building and in the process of trying to iron out the wrinkles of and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to cd999666@notformail.com on Wed May 29 12:24:47 2024
    On Wed, 29 May 2024 17:07:25 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I was >building and in the process of trying to iron out the wrinkles of and >certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA

    Lots of 2nd harmonic. Got a schematic of the clock generator?

    If so, where are you probing?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to john larkin on Wed May 29 20:49:27 2024
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's
    only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)


    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz bandpass filter, so they accept most anything.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to noreply@ademu.com on Wed May 29 13:42:13 2024
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I was
    building and in the process of trying to iron out the wrinkles of and
    certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
    bandpass filter, so they accept most anything.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Wed May 29 17:05:50 2024
    On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    What is the nature of the load?

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Cursitor Doom on Wed May 29 23:10:56 2024
    On 5/29/24 22:49, Cursitor Doom wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    If this oscillator is made to drive 50 Ohms and you don't
    provide that, internal buffer stages may saturate or do other
    weird things. If it works OK *with* the 50 Ohm load, then
    your problem is solved, no?

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Wed May 29 21:54:32 2024
    On Wed, 29 May 2024 23:10:56 +0200, Jeroen Belleman wrote:

    On 5/29/24 22:49, Cursitor Doom wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found
    the 10Mhz reference oscillator is generating an 'unsatisfactory
    waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators
    I was building and in the process of trying to iron out the wrinkles >>>>> of and certainly NOT a critical reference oscillator from a
    respected manufacturer. Can anyone tell what's most likely going on
    here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe
    cable's only 4' long! However, with the 50 ohm input enabled, the 2nd
    harmonic disappears. It's just one of those inexplicable mysteries that
    no one knows the answer to. :)

    If this oscillator is made to drive 50 Ohms and you don't provide that, internal buffer stages may saturate or do other weird things. If it
    works OK *with* the 50 Ohm load, then your problem is solved, no?

    Jeroen Belleman

    Unfortunately not. the suspicion that there was something wrong with that oscillator was my main hope of an easy fix for this analyzer. Now I have
    to go back to the drawing board and start trouble-shooting all over again.
    And it's a complex beast!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Cursitor Doom on Wed May 29 22:11:47 2024
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    That’s pretty diagnostic. There must be an LC filter on the output—mis-terminating it will cause all sorts of frequency-response whoopdedoos.

    Cheers

    Phil Hobbs


    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Wed May 29 18:59:39 2024
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>> which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I >>>>> was building and in the process of trying to iron out the wrinkles of >>>>> and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >> only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic
    disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the >outputmis-terminating it will cause all sorts of frequency-response >whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50
    ohms for positive input voltage, and say 10 Kohm for negative. At the
    very least one could get an inverted reflection on negative.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From boB@21:1/5 to cd999666@notformail.com on Wed May 29 18:19:40 2024
    On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)


    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
    bandpass filter, so they accept most anything.

    Weird but I'm not surprised that 4 feet if coax, unloaded at 10 MHz
    gives a strange waveform. Can simulate this, I believe, in LTspice
    using the transmission line element(s).

    Learned something here though.

    boB
    AZ

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to boB on Wed May 29 20:08:58 2024
    On Wed, 29 May 2024 18:19:40 -0700, boB <boB@K7IQ.com> wrote:

    On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom ><cd999666@notformail.com> wrote:

    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>> which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I >>>>> was building and in the process of trying to iron out the wrinkles of >>>>> and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >>only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)


    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
    bandpass filter, so they accept most anything.

    Weird but I'm not surprised that 4 feet if coax, unloaded at 10 MHz
    gives a strange waveform. Can simulate this, I believe, in LTspice
    using the transmission line element(s).

    Learned something here though.

    boB
    AZ

    No txline can create frequency components that are not in the source.

    (Well, a NLTL can, but 4 feet of coax isn't a shock line.)

    But the problem, as usual, is underspecified. Maybe some driver is
    going nonlinear. A schematic would help.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt@21:1/5 to Cursitor Doom on Thu May 30 20:56:41 2024
    On 5/29/24 22:49, Cursitor Doom wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)


    maybe the oscillator is source only so without a 50R load there's no
    sink to do the low side of the sine

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From boB@21:1/5 to john larkin on Thu May 30 11:55:55 2024
    On Wed, 29 May 2024 20:08:58 -0700, john larkin <jl@650pot.com> wrote:

    On Wed, 29 May 2024 18:19:40 -0700, boB <boB@K7IQ.com> wrote:

    On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom >><cd999666@notformail.com> wrote:

    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >>>> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>>> which may be causing the device to be unable to lock it's main PLL. >>>>>> I've come across this waveshape before, but mostly with oscillators I >>>>>> was building and in the process of trying to iron out the wrinkles of >>>>>> and certainly NOT a critical reference oscillator from a respected >>>>>> manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >>>only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>disappears. It's just one of those inexplicable mysteries that no one >>>knows the answer to. :)


    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
    bandpass filter, so they accept most anything.

    Weird but I'm not surprised that 4 feet if coax, unloaded at 10 MHz
    gives a strange waveform. Can simulate this, I believe, in LTspice
    using the transmission line element(s).

    Learned something here though.

    boB
    AZ

    No txline can create frequency components that are not in the source.

    (Well, a NLTL can, but 4 feet of coax isn't a shock line.)

    But the problem, as usual, is underspecified. Maybe some driver is
    going nonlinear. A schematic would help.



    I was thinking the same thing. Non-linearity.

    But he said that when he loaded it with 50 Ohms, it went back to a
    sinewave. Maybe that non-linearity went away when it was loaded ?
    Could be some kind of termination non-linearity or even coming from
    the source with the higher levels of reflections. Can't explain it
    otherwise.

    boB

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Joe Gwinn on Thu May 30 15:02:44 2024
    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >>>> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>>> which may be causing the device to be unable to lock it's main PLL. >>>>>> I've come across this waveshape before, but mostly with oscillators I >>>>>> was building and in the process of trying to iron out the wrinkles of >>>>>> and certainly NOT a critical reference oscillator from a respected >>>>>> manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's >>> only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic
    disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    That’s pretty diagnostic. There must be an LC filter on the
    output—mis-terminating it will cause all sorts of frequency-response
    whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50
    ohms for positive input voltage, and say 10 Kohm for negative. At the
    very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Thu May 30 16:06:47 2024
    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >>>>> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>>>> which may be causing the device to be unable to lock it's main PLL. >>>>>>> I've come across this waveshape before, but mostly with oscillators I >>>>>>> was building and in the process of trying to iron out the wrinkles of >>>>>>> and certainly NOT a critical reference oscillator from a respected >>>>>>> manufacturer. Can anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic. >>>>
    I don't understand how a reflection can account for it either. THe cable's >>>> only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>> disappears. It's just one of those inexplicable mysteries that no one
    knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the
    outputmis-terminating it will cause all sorts of frequency-response
    whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50
    ohms for positive input voltage, and say 10 Kohm for negative. At the
    very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer
    service manual. The 10 MHz ref input is an amplifier driving a mixer,
    with not hint of for instance a TTL input. So, the problem must be
    elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Thu May 30 14:56:30 2024
    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >>>>>> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>>>>> which may be causing the device to be unable to lock it's main PLL. >>>>>>>> I've come across this waveshape before, but mostly with oscillators I >>>>>>>> was building and in the process of trying to iron out the wrinkles of >>>>>>>> and certainly NOT a critical reference oscillator from a respected >>>>>>>> manufacturer. Can anyone tell what's most likely going on here? >>>>>>>>
    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination. >>>>>>>
    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic. >>>>>
    I don't understand how a reflection can account for it either. THe cable's
    only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>>> disappears. It's just one of those inexplicable mysteries that no one >>>>> knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the
    outputmis-terminating it will cause all sorts of frequency-response
    whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50
    ohms for positive input voltage, and say 10 Kohm for negative. At the
    very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer
    service manual. The 10 MHz ref input is an amplifier driving a mixer,
    with not hint of for instance a TTL input. So, the problem must be >elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to john larkin on Thu May 30 18:53:29 2024
    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >>>>>>> wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>>>>>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>>>>>>> which may be causing the device to be unable to lock it's main PLL. >>>>>>>>> I've come across this waveshape before, but mostly with oscillators I >>>>>>>>> was building and in the process of trying to iron out the wrinkles of >>>>>>>>> and certainly NOT a critical reference oscillator from a respected >>>>>>>>> manufacturer. Can anyone tell what's most likely going on here? >>>>>>>>>
    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination. >>>>>>>>
    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic. >>>>>>
    I don't understand how a reflection can account for it either. THe cable's
    only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>>>> disappears. It's just one of those inexplicable mysteries that no one >>>>>> knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the
    outputmis-terminating it will cause all sorts of frequency-response >>>>> whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50 >>>> ohms for positive input voltage, and say 10 Kohm for negative. At the >>>> very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer
    service manual. The 10 MHz ref input is an amplifier driving a mixer,
    with not hint of for instance a TTL input. So, the problem must be >>elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found
    it was to look at the schematics. Look for module A22. Don't think
    search works on such images, but visual search didn't take that long.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Thu May 30 16:24:25 2024
    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL. >>>>>>>>>> I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected >>>>>>>>>> manufacturer. Can anyone tell what's most likely going on here? >>>>>>>>>>
    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination. >>>>>>>>>
    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic. >>>>>>>
    I don't understand how a reflection can account for it either. THe cable's
    only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>>>>> disappears. It's just one of those inexplicable mysteries that no one >>>>>>> knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the
    outputmis-terminating it will cause all sorts of frequency-response >>>>>> whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50 >>>>> ohms for positive input voltage, and say 10 Kohm for negative. At the >>>>> very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer
    service manual. The 10 MHz ref input is an amplifier driving a mixer, >>>with not hint of for instance a TTL input. So, the problem must be >>>elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found
    it was to look at the schematics. Look for module A22. Don't think
    search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to john larkin on Fri May 31 11:34:46 2024
    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
    10Mhz reference oscillator is generating an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's main PLL. >>>>>>>>>>> I've come across this waveshape before, but mostly with oscillators I
    was building and in the process of trying to iron out the wrinkles of
    and certainly NOT a critical reference oscillator from a respected >>>>>>>>>>> manufacturer. Can anyone tell what's most likely going on here? >>>>>>>>>>>
    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination. >>>>>>>>>>
    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe cable's
    only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic >>>>>>>> disappears. It's just one of those inexplicable mysteries that no one >>>>>>>> knows the answer to. :)

    Thats pretty diagnostic. There must be an LC filter on the
    outputmis-terminating it will cause all sorts of frequency-response >>>>>>> whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may be 50 >>>>>> ohms for positive input voltage, and say 10 Kohm for negative. At the >>>>>> very least one could get an inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer
    service manual. The 10 MHz ref input is an amplifier driving a mixer, >>>>with not hint of for instance a TTL input. So, the problem must be >>>>elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found
    it was to look at the schematics. Look for module A22. Don't think
    search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is
    where an external reference enters.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Fri May 31 17:29:47 2024
    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>> found the 10Mhz reference oscillator is generating an
    'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>> main PLL. I've come across this waveshape before, but mostly >>>>>>>>>>>> with oscillators I was building and in the process of trying >>>>>>>>>>>> to iron out the wrinkles of and certainly NOT a critical >>>>>>>>>>>> reference oscillator from a respected manufacturer. Can >>>>>>>>>>>> anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input
    enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>> inexplicable mysteries that no one knows the answer to. :)

    That’s pretty diagnostic. There must be an LC filter on the
    output—mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may >>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted reflection >>>>>>> on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// xdevs.com/doc/HP_Agilent_Keysight/ HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found
    it was to look at the schematics. Look for module A22. Don't think >>>search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, near
    the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower left region. Just above, look for INT and EXT jacks. The EXT jack is where
    an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd harmonic distortion goes away when the scope input impedance is set to 50 ohms.
    There is some slight distortion on it, but not enough to cause an out-of-
    lock error. Furthermore, since that osc is the pace-setter for every other module in every other loop in this analyzer, its failure would give rise
    to way more error messages than a mere "YTO unlock" as it stands at
    present. The manual suggests the most likely areas where the fault is
    located are in one of the boards A19, A20, A21 or A11. If A22 were the culprit, there would be over a dozen error messages.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Fri May 31 18:54:06 2024
    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>> found the 10Mhz reference oscillator is generating an
    'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>> main PLL. I've come across this waveshape before, but mostly >>>>>>>>>>>> with oscillators I was building and in the process of trying >>>>>>>>>>>> to iron out the wrinkles of and certainly NOT a critical >>>>>>>>>>>> reference oscillator from a respected manufacturer. Can >>>>>>>>>>>> anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input
    enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>> inexplicable mysteries that no one knows the answer to. :)

    That’s pretty diagnostic. There must be an LC filter on the
    output—mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a
    resistor somewhere, the impedance presented to the feed coax may >>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted reflection >>>>>>> on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// xdevs.com/doc/HP_Agilent_Keysight/ HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found
    it was to look at the schematics. Look for module A22. Don't think >>>search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, near
    the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower left region. Just above, look for INT and EXT jacks. The EXT jack is where
    an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's no detailed schematic of the oscillator itself. At least that's the case with
    the PDF version of the Service Manual I have.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Fri May 31 14:48:28 2024
    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>> main PLL. I've come across this waveshape before, but mostly >>>>>>>>>>>>> with oscillators I was building and in the process of trying >>>>>>>>>>>>> to iron out the wrinkles of and certainly NOT a critical >>>>>>>>>>>>> reference oscillator from a respected manufacturer. Can >>>>>>>>>>>>> anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input
    enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>> inexplicable mysteries that no one knows the answer to. :)

    That?s pretty diagnostic. There must be an LC filter on the
    output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted reflection >>>>>>>> on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >xdevs.com/doc/HP_Agilent_Keysight/ >HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found >>>>it was to look at the schematics. Look for module A22. Don't think >>>>search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, near
    the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower left
    region. Just above, look for INT and EXT jacks. The EXT jack is where
    an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd harmonic >distortion goes away when the scope input impedance is set to 50 ohms.
    There is some slight distortion on it, but not enough to cause an out-of- >lock error. Furthermore, since that osc is the pace-setter for every other >module in every other loop in this analyzer, its failure would give rise
    to way more error messages than a mere "YTO unlock" as it stands at
    present. The manual suggests the most likely areas where the fault is
    located are in one of the boards A19, A20, A21 or A11. If A22 were the >culprit, there would be over a dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Fri May 31 15:10:32 2024
    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>> main PLL. I've come across this waveshape before, but mostly >>>>>>>>>>>>> with oscillators I was building and in the process of trying >>>>>>>>>>>>> to iron out the wrinkles of and certainly NOT a critical >>>>>>>>>>>>> reference oscillator from a respected manufacturer. Can >>>>>>>>>>>>> anyone tell what's most likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input
    enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>> inexplicable mysteries that no one knows the answer to. :)

    That?s pretty diagnostic. There must be an LC filter on the
    output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted reflection >>>>>>>> on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >xdevs.com/doc/HP_Agilent_Keysight/ >HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I found >>>>it was to look at the schematics. Look for module A22. Don't think >>>>search works on such images, but visual search didn't take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, near
    the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower left
    region. Just above, look for INT and EXT jacks. The EXT jack is where
    an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's no >detailed schematic of the oscillator itself. At least that's the case with >the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Fri May 31 21:40:04 2024
    On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>> critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>xdevs.com/doc/HP_Agilent_Keysight/ >>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>think search works on such images, but visual search didn't take that >>>>>long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is
    where an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's no >>detailed schematic of the oscillator itself. At least that's the case
    with the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released.

    Joe Gwinn

    HP actually published at least 5 manuals of various kinds about this
    analyzer, so it's possible it's in one of the others. However, the actual service manual is where I'd expect to find it if they published it at all.
    The other titles are:

    HP 8566B Operator's Manual
    HP 8566B Installation and Verification Manual
    HP 8566B Test and Adjustments Manual
    HP 8566B Troubleshooting and Repair Manual

    So if the answers are not in *any* of the above, it'd be jolly rotten luck indeed!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Fri May 31 22:17:37 2024
    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>> critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm
    termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
    negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>xdevs.com/doc/HP_Agilent_Keysight/ >>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>think search works on such images, but visual search didn't take that >>>>>long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is
    where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd harmonic >>distortion goes away when the scope input impedance is set to 50 ohms. >>There is some slight distortion on it, but not enough to cause an
    out-of- lock error. Furthermore, since that osc is the pace-setter for >>every other module in every other loop in this analyzer, its failure
    would give rise to way more error messages than a mere "YTO unlock" as
    it stands at present. The manual suggests the most likely areas where
    the fault is located are in one of the boards A19, A20, A21 or A11. If
    A22 were the culprit, there would be over a dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms
    2.68V P-P on 1 Meg

    No issues there AFAIC.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Cursitor Doom on Sat Jun 1 00:04:27 2024
    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>> critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>> resistor somewhere, the impedance presented to the feed coax >>>>>>>>>> may be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>> negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must >>>>>>>>be elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>xdevs.com/doc/HP_Agilent_Keysight/ >>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>>think search works on such images, but visual search didn't take >>>>>>that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack
    is where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd
    harmonic distortion goes away when the scope input impedance is set to
    50 ohms. There is some slight distortion on it, but not enough to cause >>>an out-of- lock error. Furthermore, since that osc is the pace-setter
    for every other module in every other loop in this analyzer, its
    failure would give rise to way more error messages than a mere "YTO >>>unlock" as it stands at present. The manual suggests the most likely >>>areas where the fault is located are in one of the boards A19, A20, A21 >>>or A11. If A22 were the culprit, there would be over a dozen error >>>messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms 2.68V P-P on 1 Meg

    No issues there AFAIC.

    Except for some distortion. I'd have expected better spectral purity from
    a xtal reference oscillator. Perhaps I should try a different scope just
    to be sure it's not that that's at fault...

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From boB@21:1/5 to cd999666@notformail.com on Fri May 31 17:02:13 2024
    On Fri, 31 May 2024 21:40:04 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote: >>>>
    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>> critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>> negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>xdevs.com/doc/HP_Agilent_Keysight/ >>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>>think search works on such images, but visual search didn't take that >>>>>>long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is >>>> where an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's no >>>detailed schematic of the oscillator itself. At least that's the case >>>with the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released.

    Joe Gwinn

    HP actually published at least 5 manuals of various kinds about this >analyzer, so it's possible it's in one of the others. However, the actual >service manual is where I'd expect to find it if they published it at all. >The other titles are:

    HP 8566B Operator's Manual
    HP 8566B Installation and Verification Manual
    HP 8566B Test and Adjustments Manual
    HP 8566B Troubleshooting and Repair Manual

    So if the answers are not in *any* of the above, it'd be jolly rotten luck >indeed!



    Looking at that waveform again...

    Could it be that the wavform you are seeing there is not a harmonic
    but just a partial cancelation due to reflections ?

    If you look at one peak vs. the other, they look about the same time
    to me. About 1 scope division. Just the amplitude looks different on alternating cycles. A non-linearity I would think would make an even harmonic. 2nd harmonic is usually due to non 1/2 wave symetry (DC
    offset bascially)

    What was tha amplitude after you loaded it down properly ? How about
    a picture ?

    Where were you scoping this at again ?

    boB

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From boB@21:1/5 to boB on Fri May 31 17:33:51 2024
    On Fri, 31 May 2024 17:02:13 -0700, boB <boB@K7IQ.com> wrote:

    On Fri, 31 May 2024 21:40:04 -0000 (UTC), Cursitor Doom ><cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote: >>>>>
    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>>> critical reference oscillator from a respected >>>>>>>>>>>>>>>> manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>>> negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>>>>elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>>>think search works on such images, but visual search didn't take that >>>>>>>long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is >>>>> where an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's no >>>>detailed schematic of the oscillator itself. At least that's the case >>>>with the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released.

    Joe Gwinn

    HP actually published at least 5 manuals of various kinds about this >>analyzer, so it's possible it's in one of the others. However, the actual >>service manual is where I'd expect to find it if they published it at all. >>The other titles are:

    HP 8566B Operator's Manual
    HP 8566B Installation and Verification Manual
    HP 8566B Test and Adjustments Manual
    HP 8566B Troubleshooting and Repair Manual

    So if the answers are not in *any* of the above, it'd be jolly rotten luck >>indeed!



    Looking at that waveform again...

    Could it be that the wavform you are seeing there is not a harmonic
    but just a partial cancelation due to reflections ?

    If you look at one peak vs. the other, they look about the same time
    to me. About 1 scope division. Just the amplitude looks different on >alternating cycles. A non-linearity I would think would make an even >harmonic.

    I thought I said the wrong thing ! I mean odd harmonic(s) from a non-linearity.


    2nd harmonic is usually due to non 1/2 wave symetry (DC
    offset bascially)


    Here, I meant even harmonic(s) not just second harmonic.

    It's rather hot today in Phoenix..

    What was tha amplitude after you loaded it down properly ? How about
    a picture ?

    Where were you scoping this at again ?

    boB

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to boB on Sat Jun 1 12:07:45 2024
    On Fri, 31 May 2024 17:33:51 -0700, boB wrote:

    On Fri, 31 May 2024 17:02:13 -0700, boB <boB@K7IQ.com> wrote:

    On Fri, 31 May 2024 21:40:04 -0000 (UTC), Cursitor Doom >><cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn >>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock >>>>>>>>>>>>>>>>> it's main PLL. I've come across this waveshape before, >>>>>>>>>>>>>>>>> but mostly with oscillators I was building and in the >>>>>>>>>>>>>>>>> process of trying to iron out the wrinkles of and >>>>>>>>>>>>>>>>> certainly NOT a critical reference oscillator from a >>>>>>>>>>>>>>>>> respected manufacturer. Can anyone tell what's most >>>>>>>>>>>>>>>>> likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of >>>>>>>>>>>>>> those inexplicable mysteries that no one knows the answer >>>>>>>>>>>>>> to. :)

    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with >>>>>>>>>>>> a resistor somewhere, the impedance presented to the feed >>>>>>>>>>>> coax may be 50 ohms for positive input voltage, and say 10 >>>>>>>>>>>> Kohm for negative. At the very least one could get an >>>>>>>>>>>> inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must >>>>>>>>>>be elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>>found it was to look at the schematics. Look for module A22. >>>>>>>>Don't think search works on such images, but visual search didn't >>>>>>>>take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, >>>>>> near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower >>>>>> left region. Just above, look for INT and EXT jacks. The EXT jack >>>>>> is where an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's >>>>>no detailed schematic of the oscillator itself. At least that's the >>>>>case with the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released.

    Joe Gwinn

    HP actually published at least 5 manuals of various kinds about this >>>analyzer, so it's possible it's in one of the others. However, the
    actual service manual is where I'd expect to find it if they published
    it at all.
    The other titles are:

    HP 8566B Operator's Manual HP 8566B Installation and Verification
    Manual HP 8566B Test and Adjustments Manual HP 8566B Troubleshooting
    and Repair Manual

    So if the answers are not in *any* of the above, it'd be jolly rotten >>>luck indeed!



    Looking at that waveform again...

    Could it be that the wavform you are seeing there is not a harmonic but >>just a partial cancelation due to reflections ?

    If you look at one peak vs. the other, they look about the same time to
    me. About 1 scope division. Just the amplitude looks different on >>alternating cycles. A non-linearity I would think would make an even >>harmonic.

    I thought I said the wrong thing ! I mean odd harmonic(s) from a non-linearity.


    2nd harmonic is usually due to non 1/2 wave symetry (DC
    offset bascially)


    Here, I meant even harmonic(s) not just second harmonic.

    It's rather hot today in Phoenix..

    1. Everybody makes careless mistakes.
    2. I don't need high temperatures to make them!

    I've taken a shot of the waveform into the 50 ohm input. It's around 850mV peak-peak. Hopefully the slight distortion I spoke about is visible; the slightly more leisurely negative-going excursions WRT their positive-going counterparts. So it's not a pure sine wave as one would expect. Does it
    matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Cursitor Doom on Sat Jun 1 15:44:17 2024
    On 6/1/24 14:07, Cursitor Doom wrote:
    On Fri, 31 May 2024 17:33:51 -0700, boB wrote:

    On Fri, 31 May 2024 17:02:13 -0700, boB <boB@K7IQ.com> wrote:

    On Fri, 31 May 2024 21:40:04 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn
    <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>>> wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn
    <joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs >>>>>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock >>>>>>>>>>>>>>>>>> it's main PLL. I've come across this waveshape before, >>>>>>>>>>>>>>>>>> but mostly with oscillators I was building and in the >>>>>>>>>>>>>>>>>> process of trying to iron out the wrinkles of and >>>>>>>>>>>>>>>>>> certainly NOT a critical reference oscillator from a >>>>>>>>>>>>>>>>>> respected manufacturer. Can anyone tell what's most >>>>>>>>>>>>>>>>>> likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of >>>>>>>>>>>>>>> those inexplicable mysteries that no one knows the answer >>>>>>>>>>>>>>> to. :)

    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with >>>>>>>>>>>>> a resistor somewhere, the impedance presented to the feed >>>>>>>>>>>>> coax may be 50 ohms for positive input voltage, and say 10 >>>>>>>>>>>>> Kohm for negative. At the very least one could get an >>>>>>>>>>>>> inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things. >>>>>>>>>>>
    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>>> service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>>> mixer,
    with not hint of for instance a TTL input. So, the problem must >>>>>>>>>>> be elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>>> xdevs.com/doc/HP_Agilent_Keysight/
    HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>>> found it was to look at the schematics. Look for module A22. >>>>>>>>> Don't think search works on such images, but visual search didn't >>>>>>>>> take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, >>>>>>> near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower >>>>>>> left region. Just above, look for INT and EXT jacks. The EXT jack >>>>>>> is where an external reference enters.

    Joe Gwinn

    It's just a block diagram of the reference oscillator module. There's >>>>>> no detailed schematic of the oscillator itself. At least that's the >>>>>> case with the PDF version of the Service Manual I have.

    It's probably in the book that I don't have, if it was ever released. >>>>>
    Joe Gwinn

    HP actually published at least 5 manuals of various kinds about this
    analyzer, so it's possible it's in one of the others. However, the
    actual service manual is where I'd expect to find it if they published >>>> it at all.
    The other titles are:

    HP 8566B Operator's Manual HP 8566B Installation and Verification
    Manual HP 8566B Test and Adjustments Manual HP 8566B Troubleshooting
    and Repair Manual

    So if the answers are not in *any* of the above, it'd be jolly rotten
    luck indeed!



    Looking at that waveform again...

    Could it be that the wavform you are seeing there is not a harmonic but
    just a partial cancelation due to reflections ?

    If you look at one peak vs. the other, they look about the same time to
    me. About 1 scope division. Just the amplitude looks different on
    alternating cycles. A non-linearity I would think would make an even
    harmonic.

    I thought I said the wrong thing ! I mean odd harmonic(s) from a
    non-linearity.


    2nd harmonic is usually due to non 1/2 wave symetry (DC
    offset bascially)


    Here, I meant even harmonic(s) not just second harmonic.

    It's rather hot today in Phoenix..

    1. Everybody makes careless mistakes.
    2. I don't need high temperatures to make them!

    I've taken a shot of the waveform into the 50 ohm input. It's around 850mV peak-peak. Hopefully the slight distortion I spoke about is visible; the slightly more leisurely negative-going excursions WRT their positive-going counterparts. So it's not a pure sine wave as one would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Sat Jun 1 16:34:16 2024
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around
    850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as one
    would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is 0.425x0.636 = 0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find it,
    that is, as PDF manuals are a nightmare to navigate IME.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Sat Jun 1 14:28:35 2024
    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote: >>>>
    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've >>>>>>>>>>>>>>> found the 10Mhz reference oscillator is generating an >>>>>>>>>>>>>>> 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>> critical reference oscillator from a respected
    manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd >>>>>>>>>>>>> harmonic.

    I don't understand how a reflection can account for it either. >>>>>>>>>>>> THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>> resistor somewhere, the impedance presented to the feed coax may >>>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>> negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must be >>>>>>>>elsewhere. Or, it's just busted.

    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>xdevs.com/doc/HP_Agilent_Keysight/ >>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>found it was to look at the schematics. Look for module A22. Don't >>>>>>think search works on such images, but visual search didn't take that >>>>>>long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack is >>>> where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd harmonic >>>distortion goes away when the scope input impedance is set to 50 ohms. >>>There is some slight distortion on it, but not enough to cause an
    out-of- lock error. Furthermore, since that osc is the pace-setter for >>>every other module in every other loop in this analyzer, its failure >>>would give rise to way more error messages than a mere "YTO unlock" as
    it stands at present. The manual suggests the most likely areas where
    the fault is located are in one of the boards A19, A20, A21 or A11. If >>>A22 were the culprit, there would be over a dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms
    2.68V P-P on 1 Meg

    No issues there AFAIC.

    Not so fast there. It's the scope that is being set to 1 Meg or 50
    ohm, and at 1 Meg we are observing the drive into the 50 ohm input
    impedance of the EXT ref input of the spectrum analyzer.

    That 2.7 Vpp over 50 ohms is about +13 dBm, which exceeds +10 dBm. So
    the EXT input may be over-driven. Install a 5-dB inline attenuator and
    see what happens.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Sat Jun 1 19:21:29 2024
    On Sat, 01 Jun 2024 14:28:35 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>>> critical reference oscillator from a respected >>>>>>>>>>>>>>>> manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>>> resistor somewhere, the impedance presented to the feed coax >>>>>>>>>>> may be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>>> negative. At the very least one could get an inverted
    reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must >>>>>>>>>be elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>found it was to look at the schematics. Look for module A22. >>>>>>>Don't think search works on such images, but visual search didn't >>>>>>>take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge,
    near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower
    left region. Just above, look for INT and EXT jacks. The EXT jack
    is where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd >>>>harmonic distortion goes away when the scope input impedance is set to >>>>50 ohms. There is some slight distortion on it, but not enough to
    cause an out-of- lock error. Furthermore, since that osc is the >>>>pace-setter for every other module in every other loop in this >>>>analyzer, its failure would give rise to way more error messages than
    a mere "YTO unlock" as it stands at present. The manual suggests the >>>>most likely areas where the fault is located are in one of the boards >>>>A19, A20, A21 or A11. If A22 were the culprit, there would be over a >>>>dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms 2.68V P-P on 1 Meg

    No issues there AFAIC.

    Not so fast there. It's the scope that is being set to 1 Meg or 50 ohm,
    and at 1 Meg we are observing the drive into the 50 ohm input impedance
    of the EXT ref input of the spectrum analyzer.

    Unless I misunderstand what you're saying, that's not the case, though.
    What we are observing is the output of the analyzer's 10Mhz reference oscillator taken from a BNC socket on the rear of it which HP have
    thoughtfully provided and fed directly into a scope switchable between 1M
    and 50 Ohms.

    That 2.7 Vpp over 50 ohms is about +13 dBm, which exceeds +10 dBm. So
    the EXT input may be over-driven. Install a 5-dB inline attenuator and
    see what happens.

    It's not an external input. They've put it there in order to make it easy
    to check the frequency of the reference oscillator and adjust it to
    precisely 10.000000Mhz if necessary (after a *minimum* 72 hour warm-up!)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Sat Jun 1 17:18:03 2024
    On Sat, 1 Jun 2024 19:21:29 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sat, 01 Jun 2024 14:28:35 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock it's >>>>>>>>>>>>>>>>> main PLL. I've come across this waveshape before, but >>>>>>>>>>>>>>>>> mostly with oscillators I was building and in the process >>>>>>>>>>>>>>>>> of trying to iron out the wrinkles of and certainly NOT a >>>>>>>>>>>>>>>>> critical reference oscillator from a respected >>>>>>>>>>>>>>>>> manufacturer. Can anyone tell what's most likely going on >>>>>>>>>>>>>>>>> here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of those >>>>>>>>>>>>>> inexplicable mysteries that no one knows the answer to. :) >>>>>>>>>>>>>
    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with a >>>>>>>>>>>> resistor somewhere, the impedance presented to the feed coax >>>>>>>>>>>> may be 50 ohms for positive input voltage, and say 10 Kohm for >>>>>>>>>>>> negative. At the very least one could get an inverted >>>>>>>>>>>> reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things.

    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem must >>>>>>>>>>be elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>>found it was to look at the schematics. Look for module A22. >>>>>>>>Don't think search works on such images, but visual search didn't >>>>>>>>take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, >>>>>> near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower >>>>>> left region. Just above, look for INT and EXT jacks. The EXT jack >>>>>> is where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd >>>>>harmonic distortion goes away when the scope input impedance is set to >>>>>50 ohms. There is some slight distortion on it, but not enough to >>>>>cause an out-of- lock error. Furthermore, since that osc is the >>>>>pace-setter for every other module in every other loop in this >>>>>analyzer, its failure would give rise to way more error messages than >>>>>a mere "YTO unlock" as it stands at present. The manual suggests the >>>>>most likely areas where the fault is located are in one of the boards >>>>>A19, A20, A21 or A11. If A22 were the culprit, there would be over a >>>>>dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms 2.68V P-P on 1 Meg

    No issues there AFAIC.

    Not so fast there. It's the scope that is being set to 1 Meg or 50 ohm,
    and at 1 Meg we are observing the drive into the 50 ohm input impedance
    of the EXT ref input of the spectrum analyzer.

    Unless I misunderstand what you're saying, that's not the case, though.
    What we are observing is the output of the analyzer's 10Mhz reference >oscillator taken from a BNC socket on the rear of it which HP have >thoughtfully provided and fed directly into a scope switchable between 1M
    and 50 Ohms.

    That 2.7 Vpp over 50 ohms is about +13 dBm, which exceeds +10 dBm. So
    the EXT input may be over-driven. Install a 5-dB inline attenuator and
    see what happens.

    It's not an external input. They've put it there in order to make it easy
    to check the frequency of the reference oscillator and adjust it to
    precisely 10.000000Mhz if necessary (after a *minimum* 72 hour warm-up!)

    Maybe. But it's simpler to just try the attenuator.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Sat Jun 1 21:46:10 2024
    On Sat, 01 Jun 2024 17:18:03 -0400, Joe Gwinn wrote:

    On Sat, 1 Jun 2024 19:21:29 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sat, 01 Jun 2024 14:28:35 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com>
    wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn >>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs >>>>>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock >>>>>>>>>>>>>>>>>> it's main PLL. I've come across this waveshape before, >>>>>>>>>>>>>>>>>> but mostly with oscillators I was building and in the >>>>>>>>>>>>>>>>>> process of trying to iron out the wrinkles of and >>>>>>>>>>>>>>>>>> certainly NOT a critical reference oscillator from a >>>>>>>>>>>>>>>>>> respected manufacturer. Can anyone tell what's most >>>>>>>>>>>>>>>>>> likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of >>>>>>>>>>>>>>> those inexplicable mysteries that no one knows the answer >>>>>>>>>>>>>>> to. :)

    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>>> output?mis-terminating it will cause all sorts of
    frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with >>>>>>>>>>>>> a resistor somewhere, the impedance presented to the feed >>>>>>>>>>>>> coax may be 50 ohms for positive input voltage, and say 10 >>>>>>>>>>>>> Kohm for negative. At the very least one could get an >>>>>>>>>>>>> inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things. >>>>>>>>>>>
    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem >>>>>>>>>>>must be elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>>>found it was to look at the schematics. Look for module A22. >>>>>>>>>Don't think search works on such images, but visual search didn't >>>>>>>>>take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, >>>>>>> near the bottom, which is not marked as a page X of Y, but is.

    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower >>>>>>> left region. Just above, look for INT and EXT jacks. The EXT
    jack is where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd >>>>>>harmonic distortion goes away when the scope input impedance is set >>>>>>to 50 ohms. There is some slight distortion on it, but not enough to >>>>>>cause an out-of- lock error. Furthermore, since that osc is the >>>>>>pace-setter for every other module in every other loop in this >>>>>>analyzer, its failure would give rise to way more error messages >>>>>>than a mere "YTO unlock" as it stands at present. The manual >>>>>>suggests the most likely areas where the fault is located are in one >>>>>>of the boards A19, A20, A21 or A11. If A22 were the culprit, there >>>>>>would be over a dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two
    castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms 2.68V P-P on 1 Meg

    No issues there AFAIC.

    Not so fast there. It's the scope that is being set to 1 Meg or 50
    ohm,
    and at 1 Meg we are observing the drive into the 50 ohm input
    impedance of the EXT ref input of the spectrum analyzer.

    Unless I misunderstand what you're saying, that's not the case, though. >>What we are observing is the output of the analyzer's 10Mhz reference >>oscillator taken from a BNC socket on the rear of it which HP have >>thoughtfully provided and fed directly into a scope switchable between
    1M and 50 Ohms.

    That 2.7 Vpp over 50 ohms is about +13 dBm, which exceeds +10 dBm. So
    the EXT input may be over-driven. Install a 5-dB inline attenuator and
    see what happens.

    It's not an external input. They've put it there in order to make it
    easy to check the frequency of the reference oscillator and adjust it to >>precisely 10.000000Mhz if necessary (after a *minimum* 72 hour warm-up!)

    Maybe. But it's simpler to just try the attenuator.

    Joe Gwinn

    If I can find a reverse attenuator, I'd be happy to try it.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to Cursitor Doom on Sat Jun 1 22:00:58 2024
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around
    850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as one
    would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be corrected, but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is 0.425x0.636 = 0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?



    --
    piglet

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Sat Jun 1 18:03:01 2024
    On Sat, 1 Jun 2024 21:46:10 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sat, 01 Jun 2024 17:18:03 -0400, Joe Gwinn wrote:

    On Sat, 1 Jun 2024 19:21:29 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sat, 01 Jun 2024 14:28:35 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 22:17:37 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 14:48:28 -0400, Joe Gwinn wrote:

    On Fri, 31 May 2024 17:29:47 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:

    On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> >>>>>>>> wrote:

    On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn >>>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com> >>>>>>>>>>wrote:

    On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn >>>>>>>>>>><joegwinn@comcast.net>
    wrote:

    On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs >>>>>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-05-29 18:59, Joe Gwinn wrote:
    On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs >>>>>>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>>>
    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck >>>>>>>>>>>>>>>>> <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote: >>>>>>>>>>>>>>>>>>> Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, >>>>>>>>>>>>>>>>>>> I've found the 10Mhz reference oscillator is generating >>>>>>>>>>>>>>>>>>> an 'unsatisfactory waveform'
    which may be causing the device to be unable to lock >>>>>>>>>>>>>>>>>>> it's main PLL. I've come across this waveshape before, >>>>>>>>>>>>>>>>>>> but mostly with oscillators I was building and in the >>>>>>>>>>>>>>>>>>> process of trying to iron out the wrinkles of and >>>>>>>>>>>>>>>>>>> certainly NOT a critical reference oscillator from a >>>>>>>>>>>>>>>>>>> respected manufacturer. Can anyone tell what's most >>>>>>>>>>>>>>>>>>> likely going on here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm >>>>>>>>>>>>>>>>>> termination.

    Arie

    If the drive is a sine wave, a cable can't generate that >>>>>>>>>>>>>>>>> 2nd harmonic.

    I don't understand how a reflection can account for it >>>>>>>>>>>>>>>> either.
    THe cable's only 4' long! However, with the 50 ohm input >>>>>>>>>>>>>>>> enabled, the 2nd harmonic disappears. It's just one of >>>>>>>>>>>>>>>> those inexplicable mysteries that no one knows the answer >>>>>>>>>>>>>>>> to. :)

    That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>>>> output?mis-terminating it will cause all sorts of >>>>>>>>>>>>>>> frequency-response whoopdedoos.

    It also occurs to me that if there is a diode in series with >>>>>>>>>>>>>> a resistor somewhere, the impedance presented to the feed >>>>>>>>>>>>>> coax may be 50 ohms for positive input voltage, and say 10 >>>>>>>>>>>>>> Kohm for negative. At the very least one could get an >>>>>>>>>>>>>> inverted reflection on negative.

    Joe Gwinn

    Yeah, or an emitter follower. Good point.

    Plus some LC filter wiggles, to distort and smooth things. >>>>>>>>>>>>
    I dug around and found a copy of the HP 8566B spectrum analyzer >>>>>>>>>>>>service manual. The 10 MHz ref input is an amplifier driving a >>>>>>>>>>>>mixer,
    with not hint of for instance a TTL input. So, the problem >>>>>>>>>>>>must be elsewhere. Or, it's just busted.
    .<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https:// >>>>>>>xdevs.com/doc/HP_Agilent_Keysight/ >>>>>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>

    Joe Gwinn

    334 pages! Where is the issue?

    The pagination was unclear, so I didn't see a way to say. How I >>>>>>>>>>found it was to look at the schematics. Look for module A22. >>>>>>>>>>Don't think search works on such images, but visual search didn't >>>>>>>>>>take that long.

    Joe Gwinn

    Too much work for free consulting.

    I took another look. There is a page reference on the right edge, >>>>>>>> near the bottom, which is not marked as a page X of Y, but is. >>>>>>>>
    Anyway, look at pages 59 and 77. At 77, look for A22 in the lower >>>>>>>> left region. Just above, look for INT and EXT jacks. The EXT >>>>>>>> jack is where an external reference enters.

    Joe Gwinn

    I don't believe the 10Mhz ref osc is the problem, John. The 2nd >>>>>>>harmonic distortion goes away when the scope input impedance is set >>>>>>>to 50 ohms. There is some slight distortion on it, but not enough to >>>>>>>cause an out-of- lock error. Furthermore, since that osc is the >>>>>>>pace-setter for every other module in every other loop in this >>>>>>>analyzer, its failure would give rise to way more error messages >>>>>>>than a mere "YTO unlock" as it stands at present. The manual >>>>>>>suggests the most likely areas where the fault is located are in one >>>>>>>of the boards A19, A20, A21 or A11. If A22 were the culprit, there >>>>>>>would be over a dozen error messages.

    What is the 10 MHz signal power level at the EXT input in these two >>>>>> castes, 1 Mohm and 50 Ohm? The expected range is 0 to +10 dBm.

    Joe Gwinn

    7.68dBm on 50 Ohms 2.68V P-P on 1 Meg

    No issues there AFAIC.

    Not so fast there. It's the scope that is being set to 1 Meg or 50
    ohm,
    and at 1 Meg we are observing the drive into the 50 ohm input
    impedance of the EXT ref input of the spectrum analyzer.

    Unless I misunderstand what you're saying, that's not the case, though. >>>What we are observing is the output of the analyzer's 10Mhz reference >>>oscillator taken from a BNC socket on the rear of it which HP have >>>thoughtfully provided and fed directly into a scope switchable between
    1M and 50 Ohms.

    That 2.7 Vpp over 50 ohms is about +13 dBm, which exceeds +10 dBm. So >>>> the EXT input may be over-driven. Install a 5-dB inline attenuator and >>>> see what happens.

    It's not an external input. They've put it there in order to make it
    easy to check the frequency of the reference oscillator and adjust it to >>>precisely 10.000000Mhz if necessary (after a *minimum* 72 hour warm-up!)

    Maybe. But it's simpler to just try the attenuator.

    Joe Gwinn

    If I can find a reverse attenuator, I'd be happy to try it.

    I don't think you need such a thing. Inline attenuators (male-female)
    are symmetric, and don't care which way the signal travels.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to piglet on Sat Jun 1 22:24:37 2024
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around
    850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as one >>>> would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be corrected, >> but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is 0.425x0.636 = >> 0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find it,
    that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.

    --
    piglet

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to piglet on Sun Jun 2 10:32:58 2024
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around
    850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as
    one would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find
    it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly speaking
    IIRC, so that's why I took the average figure; not that it makes much difference in practice. it does seem a bit on the low side, but despite
    reading through the most likely sources (the service manual and the trouble-shooting/repair manual) I can find nothing stated for what that
    signal level should be! This may be due to the user-unfriendliness of very large PDF manuals; I just don't know. Anyway, not very satisfactory! Later today I plan to do a direct power meter measurement of the ref osc (since
    none of us here seem to agree on what 850mV vs 50 ohms equates to!!)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to Cursitor Doom on Sun Jun 2 11:17:58 2024
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around >>>>> 850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as
    one would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find
    it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly speaking IIRC, so that's why I took the average figure; not that it makes much difference in practice. it does seem a bit on the low side, but despite reading through the most likely sources (the service manual and the trouble-shooting/repair manual) I can find nothing stated for what that signal level should be! This may be due to the user-unfriendliness of very large PDF manuals; I just don't know. Anyway, not very satisfactory! Later today I plan to do a direct power meter measurement of the ref osc (since none of us here seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why not measure the peak to peak voltage on the scope and power on the power meter
    and see which calculation 0.636 vs 0.707 gives the closest agreement?


    --
    piglet

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to piglet on Sun Jun 2 13:49:16 2024
    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's around >>>>> 850mV peak-peak. Hopefully the slight distortion I spoke about is
    visible; the slightly more leisurely negative-going excursions WRT
    their positive-going counterparts. So it's not a pure sine wave as one >>>>> would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 Ohms. >>>> Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be corrected, >>> but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is 0.425x0.636 = >>> 0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find it, >>> that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    What's the issue with RMS vs. average?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Sun Jun 2 12:09:48 2024
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke
    about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a
    pure sine wave as one would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find
    it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm
    ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power of
    that oscillator with my HP RF power meter and it comes out at 1.74mW (or
    about +2.5dBm off the top of my head). Seems a tad on the low side, but I
    can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they talk about "RMS Watts" is actually *average* power. I found this on the web
    which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to John R Walliker on Sun Jun 2 12:12:53 2024
    On Sun, 2 Jun 2024 13:00:21 +0100, John R Walliker wrote:

    On 02/06/2024 12:31, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>> about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a >>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators
    most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can
    find it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low
    side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find
    nothing stated for what that signal level should be! This may be due
    to the user-unfriendliness of very large PDF manuals; I just don't
    know. Anyway, not very satisfactory! Later today I plan to do a
    direct power meter measurement of the ref osc (since none of us here
    seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why
    not measure the peak to peak voltage on the scope and power on the
    power meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that
    power meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be
    accurate enough to meaningfully test your otherwise fine suggestion.

    I have an 8566B which is currently not working. Both the status leds on
    the front panel at the bottom are red. I haven't started to investigate
    yet.
    The fault developed slowly. At first it would sometimes work, then progressively less often and now never.
    However, if the signal being discussed is available on the rear panel I
    could measure mine and see what it looks like and what voltage is
    delivered.
    John

    Yes, that could be very helpful, John, since your fault is clearly totally different to mine. Peak to peak volts into 50 ohms on a scope will be fine
    if don't have access to an RF power meter.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to piglet on Sun Jun 2 11:31:33 2024
    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke
    about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a
    pure sine wave as one would expect. Does it matter? I don't know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most
    often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find
    it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm
    ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low side,
    but despite reading through the most likely sources (the service manual
    and the trouble-shooting/repair manual) I can find nothing stated for
    what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know.
    Anyway, not very satisfactory! Later today I plan to do a direct power
    meter measurement of the ref osc (since none of us here seem to agree
    on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why
    not measure the peak to peak voltage on the scope and power on the power meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate enough to meaningfully test your otherwise fine suggestion.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Doom on Sun Jun 2 12:34:29 2024
    On a sunny day (Sun, 2 Jun 2024 12:12:53 -0000 (UTC)) it happened Cursitor
    Doom <cd999666@notformail.com> wrote in <v3hnk5$3bda7$2@dont-email.me>:

    Peak to peak volts into 50 ohms on a scope will be fine
    if don't have access to an RF power meter.

    No idea what you are up to,
    but effective power can me measured this way:
    signal into dummy load, measure temperature rise of dummy load.
    Now try same with DC on dummy load, measure temperature rise
    set DC voltage to same temperature rise.
    Ohm's law gives you Watts,
    https://panteltje.nl/pub/250W_1_GHz_dummy_load_IMG_4563.JPG
    Or build you own power meter

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Cursitor Doom on Sun Jun 2 12:59:30 2024
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke
    about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a
    pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power of that oscillator with my HP RF power meter and it comes out at 1.74mW (or about +2.5dBm off the top of my head). Seems a tad on the low side, but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they talk about "RMS Watts" is actually *average* power. I found this on the web
    which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/


    It’s really not this hard.

    “RMS” stands for “root mean square”, which is a shorthand description of
    how you calculate the power delivered by an arbitrary voltage waveform (or equivalently current) in a resistive circuit.

    You square the instantaneous voltage, compute the mean (I. e. time
    average), and then take the square root.

    All those fudge factors like 0.5, 0.636, 0.707, and so forth, can be useful
    for quick calculations, but they just summarize the results of the above procedure _for_specific_situations_. Without first doing the math, and understanding the situation, they’re worse than useless.

    The ‘rms power’ thing came as a response to lying advertisements for stereo systems, starting in the 1970s iirc. Crappy stereos were advertised as producing “250 watts PMP”, for “peak music power”, as though that were a
    thing. That led to very optimistic numbers, even before actual lies were
    added, which they usually were.

    People started pushing back by insisting on knowing what sine wave power
    the amp could put out continuously without distorting or overheating.

    That’s a very conservative spec, since music waveforms have a high peak/rms ratio and the ear is most sensitive to transient distortion on the peaks.
    It does have some basis in reality, though, and is easy to measure unambiguously, which cuts through the Audio BS” (tm).

    While saying “rms watts“ is indeed redundant, strictly speaking, nevertheless it’s a useful shorthand for describing audio amps, Chinese switchers, and (I suppose) power FETs.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jan Panteltje on Sun Jun 2 13:51:31 2024
    On Sun, 02 Jun 2024 12:34:29 GMT, Jan Panteltje wrote:

    On a sunny day (Sun, 2 Jun 2024 12:12:53 -0000 (UTC)) it happened
    Cursitor Doom <cd999666@notformail.com> wrote in <v3hnk5$3bda7$2@dont-email.me>:

    Peak to peak volts into 50 ohms on a scope will be fine if don't have >>access to an RF power meter.

    No idea what you are up to,
    but effective power can me measured this way:
    signal into dummy load, measure temperature rise of dummy load.
    Now try same with DC on dummy load, measure temperature rise set DC
    voltage to same temperature rise.

    My old HP RF power meter uses this principle. It has a thermistor sensor
    head which is remarkably sensitive down into the microwatt range. Not only that, but there isn't any noticeable thermal lag, even at very low power levels, so the meter needle instantly flicks over to give the power
    reading. I've often wondered how they do that. More modern meters use a different principle IIRC.

    Ohm's law gives you Watts,
    https://panteltje.nl/pub/250W_1_GHz_dummy_load_IMG_4563.JPG
    Or build you own power meter

    Building myown RF power meter to emulate what a commercial one can do is
    way above my capabilities, sadly, Jan.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Phil Hobbs on Sun Jun 2 13:53:55 2024
    On Sun, 2 Jun 2024 12:59:30 -0000 (UTC), Phil Hobbs wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>> about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a >>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators
    most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can
    find it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power
    of that oscillator with my HP RF power meter and it comes out at 1.74mW
    (or about +2.5dBm off the top of my head). Seems a tad on the low side,
    but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they
    talk about "RMS Watts" is actually *average* power. I found this on the
    web which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/


    It’s really not this hard.

    “RMS” stands for “root mean square”, which is a shorthand description of
    how you calculate the power delivered by an arbitrary voltage waveform
    (or equivalently current) in a resistive circuit.

    You square the instantaneous voltage, compute the mean (I. e. time
    average), and then take the square root.

    All those fudge factors like 0.5, 0.636, 0.707, and so forth, can be
    useful for quick calculations, but they just summarize the results of
    the above procedure _for_specific_situations_. Without first doing the
    math, and understanding the situation, they’re worse than useless.

    The ‘rms power’ thing came as a response to lying advertisements for stereo systems, starting in the 1970s iirc. Crappy stereos were
    advertised as producing “250 watts PMP”, for “peak music power”, as though that were a thing. That led to very optimistic numbers, even
    before actual lies were added, which they usually were.

    People started pushing back by insisting on knowing what sine wave power
    the amp could put out continuously without distorting or overheating.

    That’s a very conservative spec, since music waveforms have a high
    peak/rms ratio and the ear is most sensitive to transient distortion on
    the peaks.
    It does have some basis in reality, though, and is easy to measure unambiguously, which cuts through the Audio BS” (tm).

    While saying “rms watts“ is indeed redundant, strictly speaking, nevertheless it’s a useful shorthand for describing audio amps, Chinese switchers, and (I suppose) power FETs.

    Cheers

    Phil Hobbs

    Phil, I believe you also have an 8566B. Do you know what the 10Mhz
    reference oscillator output level should be? Is yours anything close to +2.5dBm?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Sun Jun 2 16:55:28 2024
    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>> about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a >>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators
    most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can
    find it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low
    side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find
    nothing stated for what that signal level should be! This may be due
    to the user-unfriendliness of very large PDF manuals; I just don't
    know. Anyway, not very satisfactory! Later today I plan to do a
    direct power meter measurement of the ref osc (since none of us here
    seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why
    not measure the peak to peak voltage on the scope and power on the
    power meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that
    power meter hasn't been calibrated for "quite a while" so to speak. :) >>It'll give a 'good enough' reading for my purposes, but won't be
    accurate enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the analyzer's allowed range. All that's needed to fix this is a 3dB inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/
    B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the
    scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or
    thereabouts and when I measured it with an actual power meter, came out at about +2.5dBm so within the range you stated; no attenuation needed
    (thanks for the range, by the way; I needed to know that).

    I've now measured the 100Mhz oscillator and that seems fine, although I
    only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz
    oscillator's output.
    So far, I've not measured anything which screams "the fault's here!" as
    all the expected signals are present - although admittedly I have many
    more to test. But certainly all the *major* signals within this complex
    beast are present. It's looking like it could be an issue with one of the
    phase detectors or LPFs. Sigh....

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Sun Jun 2 12:19:05 2024
    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke
    about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a
    pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low side,
    but despite reading through the most likely sources (the service manual
    and the trouble-shooting/repair manual) I can find nothing stated for
    what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know.
    Anyway, not very satisfactory! Later today I plan to do a direct power
    meter measurement of the ref osc (since none of us here seem to agree
    on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why
    not measure the peak to peak voltage on the scope and power on the power
    meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power >meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate >enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to boB on Sun Jun 2 17:39:45 2024
    On Wed, 29 May 2024 18:19:40 -0700, boB wrote:

    On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

    On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck
    <noreply@ademu.com>
    wrote:

    On 2024-05-29 19:07, Cursitor Doom wrote:
    Gentlemen,

    Whilst fault-finding on my HP 8566B spectrum analyzer, I've found
    the 10Mhz reference oscillator is generating an 'unsatisfactory
    waveform'
    which may be causing the device to be unable to lock it's main PLL.
    I've come across this waveshape before, but mostly with oscillators
    I was building and in the process of trying to iron out the wrinkles >>>>> of and certainly NOT a critical reference oscillator from a
    respected manufacturer. Can anyone tell what's most likely going on
    here?

    https://disk.yandex.com/i/z6fYbeVfPRK7aA


    Looks like reflections in the cable. Try the 50 Ohm termination.

    Arie

    If the drive is a sine wave, a cable can't generate that 2nd harmonic.

    I don't understand how a reflection can account for it either. THe
    cable's only 4' long! However, with the 50 ohm input enabled, the 2nd >>harmonic disappears. It's just one of those inexplicable mysteries that
    no one knows the answer to. :)


    Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
    bandpass filter, so they accept most anything.

    Weird but I'm not surprised that 4 feet if coax, unloaded at 10 MHz
    gives a strange waveform. Can simulate this, I believe, in LTspice
    using the transmission line element(s).

    Learned something here though.
    e
    I'm guessing there should have been a 50 ohm load screwed into the rear
    10Mhz reference oscillator output BNC socket when the analyzer's in use.
    There wasn't one but there is now. Unfortunately it hasn't cleared the PLL unlock issue.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Cursitor Doom on Sun Jun 2 20:05:43 2024
    On 6/2/24 14:09, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke
    about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a
    pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50
    Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power of that oscillator with my HP RF power meter and it comes out at 1.74mW (or about +2.5dBm off the top of my head). Seems a tad on the low side, but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they talk about "RMS Watts" is actually *average* power. I found this on the web
    which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/

    Average power is not the same as average voltage! Average power is
    proportional to the average of the voltage squared. It makes a
    difference!

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Sun Jun 2 14:08:48 2024
    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low
    side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find
    nothing stated for what that signal level should be! This may be due >>>>> to the user-unfriendliness of very large PDF manuals; I just don't
    know. Anyway, not very satisfactory! Later today I plan to do a
    direct power meter measurement of the ref osc (since none of us here >>>>> seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why >>>> not measure the peak to peak voltage on the scope and power on the
    power meter and see which calculation 0.636 vs 0.707 gives the closest >>>> agreement?

    It wouldn't prove anything one way or ther other, though, since that >>>power meter hasn't been calibrated for "quite a while" so to speak. :) >>>It'll give a 'good enough' reading for my purposes, but won't be
    accurate enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB inline
    attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/ >B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the
    scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or >thereabouts and when I measured it with an actual power meter, came out at >about +2.5dBm so within the range you stated; no attenuation needed
    (thanks for the range, by the way; I needed to know that).

    What we don't know is exactly how you made the various measurements.
    If you are observing the signal from the 10 MHz reference where it
    enters the analyzer, I would expect that there is a T-connector with
    the scope (set to 1 Mohm) listening in to passing signals.

    In this case, the load seen by the incoming reference is that provided
    by the input on the analyzer. Which input is +10 dBm max. If you set
    the observing scope input to 50 ohm, the reference will see a 25 ohm
    load, cutting the signal seen by the analyzer by 3 dB. Which will
    take +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is
    delivered to everybody at +13 dBm, and it is the receivers'
    responsibility to attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine, although I
    only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz
    oscillator's output.
    So far, I've not measured anything which screams "the fault's here!" as
    all the expected signals are present - although admittedly I have many
    more to test. But certainly all the *major* signals within this complex
    beast are present. It's looking like it could be an issue with one of the >phase detectors or LPFs. Sigh....

    To my eye, it does scream.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Joe Gwinn on Sun Jun 2 20:18:50 2024
    On 6/2/24 18:19, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>> about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a >>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>> ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low side, >>>> but despite reading through the most likely sources (the service manual >>>> and the trouble-shooting/repair manual) I can find nothing stated for
    what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know.
    Anyway, not very satisfactory! Later today I plan to do a direct power >>>> meter measurement of the ref osc (since none of us here seem to agree
    on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why
    not measure the peak to peak voltage on the scope and power on the power >>> meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power >> meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate
    enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.

    Joe Gwinn

    What scope picture are you looking at? I see only 0.88Vpp.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Sun Jun 2 19:37:26 2024
    On Sun, 2 Jun 2024 20:05:43 +0200, Jeroen Belleman wrote:

    On 6/2/24 14:09, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's
    around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>> about is visible; the slightly more leisurely negative-going
    excursions WRT their positive-going counterparts. So it's not a >>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators
    most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load
    impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can
    find it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
    rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power
    of that oscillator with my HP RF power meter and it comes out at 1.74mW
    (or about +2.5dBm off the top of my head). Seems a tad on the low side,
    but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they
    talk about "RMS Watts" is actually *average* power. I found this on the
    web which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/

    Average power is not the same as average voltage! Average power is proportional to the average of the voltage squared. It makes a
    difference!

    Jeroen Belleman

    Sorry, but I don't recall anyone claiming average power and average
    voltage were the same thing!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to jeroen@nospam.please on Sun Jun 2 15:44:31 2024
    On Sun, 2 Jun 2024 20:18:50 +0200, Jeroen Belleman
    <jeroen@nospam.please> wrote:

    On 6/2/24 18:19, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>> ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it
    makes much difference in practice. it does seem a bit on the low side, >>>>> but despite reading through the most likely sources (the service manual >>>>> and the trouble-shooting/repair manual) I can find nothing stated for >>>>> what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know.
    Anyway, not very satisfactory! Later today I plan to do a direct power >>>>> meter measurement of the ref osc (since none of us here seem to agree >>>>> on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why >>>> not measure the peak to peak voltage on the scope and power on the power >>>> meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power >>> meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate >>> enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.

    Joe Gwinn

    What scope picture are you looking at? I see only 0.88Vpp.

    This one, posted by CD on 1 June '24:

    .< https://disk.yandex.com/i/7cuuBimDbOIBZw>

    This is the one with the funny stuff at the bottom. If you look at
    the upper waveshape, the peak amplitude to the inflection point near
    the bottom is about 1.5 Vp, which implies 3 Vpp, which is +13 dBm into
    50 ohms. Why the inflection point? Because in a undistorted sine
    wave, the zero crossing is linear, and does not flair. The scope
    picture does not show where zero volts is, so had to use the
    inflection point.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Sun Jun 2 20:58:45 2024
    On Sun, 02 Jun 2024 14:08:48 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't >>>>>>>>>> know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it >>>>>> makes much difference in practice. it does seem a bit on the low
    side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find
    nothing stated for what that signal level should be! This may be
    due to the user-unfriendliness of very large PDF manuals; I just
    don't know. Anyway, not very satisfactory! Later today I plan to do >>>>>> a direct power meter measurement of the ref osc (since none of us
    here seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope
    why not measure the peak to peak voltage on the scope and power on
    the power meter and see which calculation 0.636 vs 0.707 gives the
    closest agreement?

    It wouldn't prove anything one way or ther other, though, since that >>>>power meter hasn't been calibrated for "quite a while" so to speak. :) >>>>It'll give a 'good enough' reading for my purposes, but won't be >>>>accurate enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/ >>B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the >>scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or >>thereabouts and when I measured it with an actual power meter, came out
    at about +2.5dBm so within the range you stated; no attenuation needed >>(thanks for the range, by the way; I needed to know that).

    What we don't know is exactly how you made the various measurements. If
    you are observing the signal from the 10 MHz reference where it enters
    the analyzer, I would expect that there is a T-connector with the scope
    (set to 1 Mohm) listening in to passing signals.

    You did ask me this before and did post an answer. See Message-ID: <v3fsbp$2u0a6$1@dont-email.me>

    You also still appear to think that the 10Mhz signal is going into the analyzer. It isn't. It's coming out. Again, see Message-ID: <v3fsbp$2u0a6$1@dont-email.me>



    In this case, the load seen by the incoming reference is that provided
    by the input on the analyzer. Which input is +10 dBm max. If you set
    the observing scope input to 50 ohm, the reference will see a 25 ohm
    load, cutting the signal seen by the analyzer by 3 dB. Which will take
    +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is delivered
    to everybody at +13 dBm, and it is the receivers' responsibility to
    attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine, although I >>only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz >>oscillator's output.
    So far, I've not measured anything which screams "the fault's here!" as
    all the expected signals are present - although admittedly I have many
    more to test. But certainly all the *major* signals within this complex >>beast are present. It's looking like it could be an issue with one of
    the phase detectors or LPFs. Sigh....

    To my eye, it does scream.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Joe Gwinn on Sun Jun 2 23:45:43 2024
    On 6/2/24 21:44, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 20:18:50 +0200, Jeroen Belleman
    <jeroen@nospam.please> wrote:

    On 6/2/24 18:19, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>>>>> it, that is, as PDF manuals are a nightmare to navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>>> ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it >>>>>> makes much difference in practice. it does seem a bit on the low side, >>>>>> but despite reading through the most likely sources (the service manual >>>>>> and the trouble-shooting/repair manual) I can find nothing stated for >>>>>> what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know.
    Anyway, not very satisfactory! Later today I plan to do a direct power >>>>>> meter measurement of the ref osc (since none of us here seem to agree >>>>>> on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why >>>>> not measure the peak to peak voltage on the scope and power on the power >>>>> meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power >>>> meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate >>>> enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.

    Joe Gwinn

    What scope picture are you looking at? I see only 0.88Vpp.

    This one, posted by CD on 1 June '24:

    .< https://disk.yandex.com/i/7cuuBimDbOIBZw>

    This is the one with the funny stuff at the bottom. If you look at
    the upper waveshape, the peak amplitude to the inflection point near
    the bottom is about 1.5 Vp, which implies 3 Vpp, which is +13 dBm into
    50 ohms. Why the inflection point? Because in a undistorted sine
    wave, the zero crossing is linear, and does not flair. The scope
    picture does not show where zero volts is, so had to use the
    inflection point.

    Joe Gwinn

    I'm afraid you have lost me there... I see only a roughly
    sine-shaped wave framed with cursors along the peaks being
    0.88V apart. I don't care about the DC level, only the 10MHz
    component matters. Its amplitude is only 0.44V.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Cursitor Doom on Sun Jun 2 23:31:38 2024
    On 6/2/24 21:37, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 20:05:43 +0200, Jeroen Belleman wrote:

    On 6/2/24 14:09, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be
    corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic >>>>> rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the power
    of that oscillator with my HP RF power meter and it comes out at 1.74mW
    (or about +2.5dBm off the top of my head). Seems a tad on the low side,
    but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they
    talk about "RMS Watts" is actually *average* power. I found this on the
    web which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/

    Average power is not the same as average voltage! Average power is
    proportional to the average of the voltage squared. It makes a
    difference!

    Jeroen Belleman

    Sorry, but I don't recall anyone claiming average power and average
    voltage were the same thing!

    Earlier, you said, I cite, "Average power is average volts squared
    divided by the load impedance".

    It isn't. It's RMS volts squared divided by load impedance.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Sun Jun 2 21:59:22 2024
    On Sun, 2 Jun 2024 23:31:38 +0200, Jeroen Belleman wrote:

    On 6/2/24 21:37, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 20:05:43 +0200, Jeroen Belleman wrote:

    On 6/2/24 14:09, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:

    On 6/2/24 00:24, piglet wrote:
    piglet <erichpwagner@hotmail.com> wrote:
    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't >>>>>>>>>> know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?




    Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope
    pic rather than the 0.85v figure of your message.


    To CD:

    The above is what I did. 30 + 10*log( (0.88/(2*sqrt(2)))^2 / 50) =
    2.869 dBm. Rounded to 3dBm.

    OK, thanks for that clarification. Anyway, I finally measured the
    power of that oscillator with my HP RF power meter and it comes out
    at 1.74mW (or about +2.5dBm off the top of my head). Seems a tad on
    the low side,
    but I can't find what it's supposed to be in the manual.


    What's the issue with RMS vs. average?

    When you dig into it, you find that what people really mean when they
    talk about "RMS Watts" is actually *average* power. I found this on
    the web which attempts to explain it:

    https://agcsystems.tv/rms-power-fallacy/

    Average power is not the same as average voltage! Average power is
    proportional to the average of the voltage squared. It makes a
    difference!

    Jeroen Belleman

    Sorry, but I don't recall anyone claiming average power and average
    voltage were the same thing!

    Earlier, you said, I cite, "Average power is average volts squared
    divided by the load impedance".

    It isn't. It's RMS volts squared divided by load impedance.

    Jeroen Belleman

    Thanks for that clarification.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to jeroen@nospam.please on Mon Jun 3 07:43:41 2024
    On Sun, 2 Jun 2024 23:45:43 +0200, Jeroen Belleman
    <jeroen@nospam.please> wrote:

    On 6/2/24 21:44, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 20:18:50 +0200, Jeroen Belleman
    <jeroen@nospam.please> wrote:

    On 6/2/24 18:19, Joe Gwinn wrote:
    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't know! >>>>>>>>>>>
    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into 50 >>>>>>>>>> Ohms.
    Is that what it's supposed to be? Canned reference oscillators most >>>>>>>>>> often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is >>>>>>>>> 0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can find >>>>>>>>> it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>>>> ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly >>>>>>> speaking IIRC, so that's why I took the average figure; not that it >>>>>>> makes much difference in practice. it does seem a bit on the low side, >>>>>>> but despite reading through the most likely sources (the service manual >>>>>>> and the trouble-shooting/repair manual) I can find nothing stated for >>>>>>> what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't know. >>>>>>> Anyway, not very satisfactory! Later today I plan to do a direct power >>>>>>> meter measurement of the ref osc (since none of us here seem to agree >>>>>>> on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope why >>>>>> not measure the peak to peak voltage on the scope and power on the power >>>>>> meter and see which calculation 0.636 vs 0.707 gives the closest
    agreement?

    It wouldn't prove anything one way or ther other, though, since that power
    meter hasn't been calibrated for "quite a while" so to speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be accurate >>>>> enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.

    Joe Gwinn

    What scope picture are you looking at? I see only 0.88Vpp.

    This one, posted by CD on 1 June '24:

    .< https://disk.yandex.com/i/7cuuBimDbOIBZw>

    This is the one with the funny stuff at the bottom. If you look at
    the upper waveshape, the peak amplitude to the inflection point near
    the bottom is about 1.5 Vp, which implies 3 Vpp, which is +13 dBm into
    50 ohms. Why the inflection point? Because in a undistorted sine
    wave, the zero crossing is linear, and does not flair. The scope
    picture does not show where zero volts is, so had to use the
    inflection point.

    Joe Gwinn

    I'm afraid you have lost me there... I see only a roughly
    sine-shaped wave framed with cursors along the peaks being
    0.88V apart. I don't care about the DC level, only the 10MHz
    component matters. Its amplitude is only 0.44V.

    I copied the wrong yandex.

    Try this (29 May 2024):
    .<https://disk.yandex.com/i/z6fYbeVfPRK7aA >

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to cd999666@notformail.com on Mon Jun 3 07:48:32 2024
    On Sun, 2 Jun 2024 20:58:45 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 14:08:48 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't >>>>>>>>>>> know!

    <https://disk.yandex.com/i/7cuuBimDbOIBZw>


    And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>


    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is >>>>>>>>> 0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>> +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly >>>>>>> speaking IIRC, so that's why I took the average figure; not that it >>>>>>> makes much difference in practice. it does seem a bit on the low >>>>>>> side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find >>>>>>> nothing stated for what that signal level should be! This may be >>>>>>> due to the user-unfriendliness of very large PDF manuals; I just >>>>>>> don't know. Anyway, not very satisfactory! Later today I plan to do >>>>>>> a direct power meter measurement of the ref osc (since none of us >>>>>>> here seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope >>>>>> why not measure the peak to peak voltage on the scope and power on >>>>>> the power meter and see which calculation 0.636 vs 0.707 gives the >>>>>> closest agreement?

    It wouldn't prove anything one way or ther other, though, since that >>>>>power meter hasn't been calibrated for "quite a while" so to speak. :) >>>>>It'll give a 'good enough' reading for my purposes, but won't be >>>>>accurate enough to meaningfully test your otherwise fine suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which is
    +13 dBm, a very common distribution level, but one that exceeds the
    analyzer's allowed range. All that's needed to fix this is a 3dB
    inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/ >>>B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the >>>scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or >>>thereabouts and when I measured it with an actual power meter, came out >>>at about +2.5dBm so within the range you stated; no attenuation needed >>>(thanks for the range, by the way; I needed to know that).

    What we don't know is exactly how you made the various measurements. If
    you are observing the signal from the 10 MHz reference where it enters
    the analyzer, I would expect that there is a T-connector with the scope
    (set to 1 Mohm) listening in to passing signals.

    You did ask me this before and did post an answer. See Message-ID: ><v3fsbp$2u0a6$1@dont-email.me>

    You also still appear to think that the 10Mhz signal is going into the >analyzer. It isn't. It's coming out. Again, see Message-ID: ><v3fsbp$2u0a6$1@dont-email.me>

    I did read that, but didn't know what to make of it. I think an
    annotated drawing is required.

    On this drawing, where do the various scope traces mentioned up-thread
    come from?

    Joe Gwinn






    In this case, the load seen by the incoming reference is that provided
    by the input on the analyzer. Which input is +10 dBm max. If you set
    the observing scope input to 50 ohm, the reference will see a 25 ohm
    load, cutting the signal seen by the analyzer by 3 dB. Which will take
    +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is delivered
    to everybody at +13 dBm, and it is the receivers' responsibility to
    attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine, although I >>>only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz >>>oscillator's output.
    So far, I've not measured anything which screams "the fault's here!" as >>>all the expected signals are present - although admittedly I have many >>>more to test. But certainly all the *major* signals within this complex >>>beast are present. It's looking like it could be an issue with one of
    the phase detectors or LPFs. Sigh....

    To my eye, it does scream.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Joe Gwinn on Mon Jun 3 15:43:25 2024
    On Mon, 03 Jun 2024 07:48:32 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 20:58:45 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 14:08:48 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I >>>>>>>>>>>> spoke about is visible; the slightly more leisurely
    negative-going excursions WRT their positive-going
    counterparts. So it's not a pure sine wave as one would >>>>>>>>>>>> expect. Does it matter? I don't know!

    <https://disk.yandex.com/i/7cuuBimDbOIBZw>


    And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>


    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is >>>>>>>>>> 0.425x0.636 =
    0.27V. Average power is average volts squared divided by the >>>>>>>>>> load impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I >>>>>>>>>> can find it, that is, as PDF manuals are a nightmare to
    navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>> +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly >>>>>>>> speaking IIRC, so that's why I took the average figure; not that >>>>>>>> it makes much difference in practice. it does seem a bit on the >>>>>>>> low side, but despite reading through the most likely sources
    (the service manual and the trouble-shooting/repair manual) I can >>>>>>>> find nothing stated for what that signal level should be! This >>>>>>>> may be due to the user-unfriendliness of very large PDF manuals; >>>>>>>> I just don't know. Anyway, not very satisfactory! Later today I >>>>>>>> plan to do a direct power meter measurement of the ref osc (since >>>>>>>> none of us here seem to agree on what 850mV vs 50 ohms equates >>>>>>>> to!!)





    Since you have a power meter, a signal source, and an oscilloscope >>>>>>> why not measure the peak to peak voltage on the scope and power on >>>>>>> the power meter and see which calculation 0.636 vs 0.707 gives the >>>>>>> closest agreement?

    It wouldn't prove anything one way or ther other, though, since that >>>>>>power meter hasn't been calibrated for "quite a while" so to speak. >>>>>>:)
    It'll give a 'good enough' reading for my purposes, but won't be >>>>>>accurate enough to meaningfully test your otherwise fine suggestion. >>>>>

    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which
    is +13 dBm, a very common distribution level, but one that exceeds
    the analyzer's allowed range. All that's needed to fix this is a
    3dB inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/ >>>>B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the >>>>scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or >>>>thereabouts and when I measured it with an actual power meter, came
    out at about +2.5dBm so within the range you stated; no attenuation >>>>needed (thanks for the range, by the way; I needed to know that).

    What we don't know is exactly how you made the various measurements.
    If you are observing the signal from the 10 MHz reference where it
    enters the analyzer, I would expect that there is a T-connector with
    the scope (set to 1 Mohm) listening in to passing signals.

    You did ask me this before and did post an answer. See Message-ID: >><v3fsbp$2u0a6$1@dont-email.me>

    You also still appear to think that the 10Mhz signal is going into the >>analyzer. It isn't. It's coming out. Again, see Message-ID: >><v3fsbp$2u0a6$1@dont-email.me>

    I did read that, but didn't know what to make of it. I think an
    annotated drawing is required.

    On this drawing, where do the various scope traces mentioned up-thread
    come from?

    Joe Gwinn






    In this case, the load seen by the incoming reference is that provided
    by the input on the analyzer. Which input is +10 dBm max. If you set
    the observing scope input to 50 ohm, the reference will see a 25 ohm
    load, cutting the signal seen by the analyzer by 3 dB. Which will
    take +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is
    delivered to everybody at +13 dBm, and it is the receivers'
    responsibility to attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine, although
    I only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz >>>>oscillator's output.
    So far, I've not measured anything which screams "the fault's here!"
    as all the expected signals are present - although admittedly I have >>>>many more to test. But certainly all the *major* signals within this >>>>complex beast are present. It's looking like it could be an issue with >>>>one of the phase detectors or LPFs. Sigh....

    To my eye, it does scream.

    Joe Gwinn

    Joe, I appreciate you're only trying to help, but don't worry about it. I
    don't believe the oscillator this thread relates to is causing the PLL
    unlock error so we've all gone down a bit of a rabbit hole with this one.
    I really need to look elsewhere for the culprit.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jeroen Belleman@21:1/5 to Cursitor Doom on Mon Jun 3 19:38:21 2024
    On 6/3/24 17:43, Cursitor Doom wrote:
    On Mon, 03 Jun 2024 07:48:32 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 20:58:45 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 14:08:48 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote: >>>>>>>>>>>
    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I >>>>>>>>>>>>> spoke about is visible; the slightly more leisurely
    negative-going excursions WRT their positive-going
    counterparts. So it's not a pure sine wave as one would >>>>>>>>>>>>> expect. Does it matter? I don't know!

    <https://disk.yandex.com/i/7cuuBimDbOIBZw>


    And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>


    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is >>>>>>>>>>> 0.425x0.636 =
    0.27V. Average power is average volts squared divided by the >>>>>>>>>>> load impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I >>>>>>>>>>> can find it, that is, as PDF manuals are a nightmare to
    navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>>> +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly >>>>>>>>> speaking IIRC, so that's why I took the average figure; not that >>>>>>>>> it makes much difference in practice. it does seem a bit on the >>>>>>>>> low side, but despite reading through the most likely sources >>>>>>>>> (the service manual and the trouble-shooting/repair manual) I can >>>>>>>>> find nothing stated for what that signal level should be! This >>>>>>>>> may be due to the user-unfriendliness of very large PDF manuals; >>>>>>>>> I just don't know. Anyway, not very satisfactory! Later today I >>>>>>>>> plan to do a direct power meter measurement of the ref osc (since >>>>>>>>> none of us here seem to agree on what 850mV vs 50 ohms equates >>>>>>>>> to!!)





    Since you have a power meter, a signal source, and an oscilloscope >>>>>>>> why not measure the peak to peak voltage on the scope and power on >>>>>>>> the power meter and see which calculation 0.636 vs 0.707 gives the >>>>>>>> closest agreement?

    It wouldn't prove anything one way or ther other, though, since that >>>>>>> power meter hasn't been calibrated for "quite a while" so to speak. >>>>>>> :)
    It'll give a 'good enough' reading for my purposes, but won't be >>>>>>> accurate enough to meaningfully test your otherwise fine suggestion. >>>>>>

    The 0 to +10 dBm range I mentioned came from the service manual.

    Looking at your scope picture, it looks like a 3 Vpp signal, which >>>>>> is +13 dBm, a very common distribution level, but one that exceeds >>>>>> the analyzer's allowed range. All that's needed to fix this is a
    3dB inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/
    B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far
    cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into the >>>>> scope's 1 Meg input. The 50 ohm trace is only 850mV peak-to-peak or
    thereabouts and when I measured it with an actual power meter, came
    out at about +2.5dBm so within the range you stated; no attenuation
    needed (thanks for the range, by the way; I needed to know that).

    What we don't know is exactly how you made the various measurements.
    If you are observing the signal from the 10 MHz reference where it
    enters the analyzer, I would expect that there is a T-connector with
    the scope (set to 1 Mohm) listening in to passing signals.

    You did ask me this before and did post an answer. See Message-ID:
    <v3fsbp$2u0a6$1@dont-email.me>

    You also still appear to think that the 10Mhz signal is going into the
    analyzer. It isn't. It's coming out. Again, see Message-ID:
    <v3fsbp$2u0a6$1@dont-email.me>

    I did read that, but didn't know what to make of it. I think an
    annotated drawing is required.

    On this drawing, where do the various scope traces mentioned up-thread
    come from?

    Joe Gwinn






    In this case, the load seen by the incoming reference is that provided >>>> by the input on the analyzer. Which input is +10 dBm max. If you set >>>> the observing scope input to 50 ohm, the reference will see a 25 ohm
    load, cutting the signal seen by the analyzer by 3 dB. Which will
    take +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is
    delivered to everybody at +13 dBm, and it is the receivers'
    responsibility to attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine, although >>>>> I only saw 0.61V p-p into 50 ohms, so somewhat less than the 10Mhz
    oscillator's output.
    So far, I've not measured anything which screams "the fault's here!" >>>>> as all the expected signals are present - although admittedly I have >>>>> many more to test. But certainly all the *major* signals within this >>>>> complex beast are present. It's looking like it could be an issue with >>>>> one of the phase detectors or LPFs. Sigh....

    To my eye, it does scream.

    Joe Gwinn

    Joe, I appreciate you're only trying to help, but don't worry about it. I don't believe the oscillator this thread relates to is causing the PLL
    unlock error so we've all gone down a bit of a rabbit hole with this one.
    I really need to look elsewhere for the culprit.

    For what it's worth, I found a manual on the web saying that the
    10MHz output should deliver +5dBm into 50 Ohms. It's a bit low,
    then, but I doubt that this is your problem.

    Jeroen Belleman

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to Jeroen Belleman on Mon Jun 3 17:53:50 2024
    On Mon, 3 Jun 2024 19:38:21 +0200, Jeroen Belleman wrote:

    On 6/3/24 17:43, Cursitor Doom wrote:
    On Mon, 03 Jun 2024 07:48:32 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 20:58:45 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 14:08:48 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 16:55:28 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 02 Jun 2024 12:19:05 -0400, Joe Gwinn wrote:

    On Sun, 2 Jun 2024 11:31:33 -0000 (UTC), Cursitor Doom
    <cd999666@notformail.com> wrote:

    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote: >>>>>>>>>>>>
    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. >>>>>>>>>>>>>> It's around 850mV peak-peak. Hopefully the slight
    distortion I spoke about is visible; the slightly more >>>>>>>>>>>>>> leisurely negative-going excursions WRT their
    positive-going counterparts. So it's not a pure sine wave >>>>>>>>>>>>>> as one would expect. Does it matter? I don't know! >>>>>>>>>>>>>>
    <https://disk.yandex.com/i/7cuuBimDbOIBZw>


    And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>


    The shape looks perfectly acceptable to me. This is +3dBm >>>>>>>>>>>>> into 50 Ohms.
    Is that what it's supposed to be? Canned reference
    oscillators most often deliver +13dBm, sometimes +10dBm. >>>>>>>>>>>>
    Is it? I only make it about half your figure: +1.65dBm. >>>>>>>>>>>> I admit I'm frequently prone to careless errors, so stand to >>>>>>>>>>>> be corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is >>>>>>>>>>>> 0.425x0.636 =
    0.27V. Average power is average volts squared divided by the >>>>>>>>>>>> load impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I >>>>>>>>>>>> can find it, that is, as PDF manuals are a nightmare to >>>>>>>>>>>> navigate IME.



    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>>>> +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power"
    strictly speaking IIRC, so that's why I took the average
    figure; not that it makes much difference in practice. it does >>>>>>>>>> seem a bit on the low side, but despite reading through the >>>>>>>>>> most likely sources (the service manual and the
    trouble-shooting/repair manual) I can find nothing stated for >>>>>>>>>> what that signal level should be! This may be due to the
    user-unfriendliness of very large PDF manuals; I just don't >>>>>>>>>> know. Anyway, not very satisfactory! Later today I plan to do a >>>>>>>>>> direct power meter measurement of the ref osc (since none of us >>>>>>>>>> here seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an
    oscilloscope why not measure the peak to peak voltage on the >>>>>>>>> scope and power on the power meter and see which calculation >>>>>>>>> 0.636 vs 0.707 gives the closest agreement?

    It wouldn't prove anything one way or ther other, though, since >>>>>>>> that power meter hasn't been calibrated for "quite a while" so to >>>>>>>> speak. :)
    It'll give a 'good enough' reading for my purposes, but won't be >>>>>>>> accurate enough to meaningfully test your otherwise fine
    suggestion.


    The 0 to +10 dBm range I mentioned came from the service manual. >>>>>>>
    Looking at your scope picture, it looks like a 3 Vpp signal, which >>>>>>> is +13 dBm, a very common distribution level, but one that exceeds >>>>>>> the analyzer's allowed range. All that's needed to fix this is a >>>>>>> 3dB inline attenuator. Here is one for SMA connectors:

    .<https://www.amazon.com/MWRF-Source-Male-Female-Attenuator/dp/
    B07MP9D9GC?th=1>

    Just buying a few of these and doing some experiments will be far >>>>>>> cheaper and faster than the various alternatives discussed.t

    Joe Gwinn

    I think you're looking at the first picture with the signal into
    the scope's 1 Meg input. The 50 ohm trace is only 850mV
    peak-to-peak or thereabouts and when I measured it with an actual
    power meter, came out at about +2.5dBm so within the range you
    stated; no attenuation needed (thanks for the range, by the way; I >>>>>> needed to know that).

    What we don't know is exactly how you made the various measurements. >>>>> If you are observing the signal from the 10 MHz reference where it
    enters the analyzer, I would expect that there is a T-connector with >>>>> the scope (set to 1 Mohm) listening in to passing signals.

    You did ask me this before and did post an answer. See Message-ID:
    <v3fsbp$2u0a6$1@dont-email.me>

    You also still appear to think that the 10Mhz signal is going into
    the analyzer. It isn't. It's coming out. Again, see Message-ID:
    <v3fsbp$2u0a6$1@dont-email.me>

    I did read that, but didn't know what to make of it. I think an
    annotated drawing is required.

    On this drawing, where do the various scope traces mentioned up-thread
    come from?

    Joe Gwinn






    In this case, the load seen by the incoming reference is that
    provided by the input on the analyzer. Which input is +10 dBm max.
    If you set the observing scope input to 50 ohm, the reference will
    see a 25 ohm load, cutting the signal seen by the analyzer by 3 dB.
    Which will take +13 dBm down to +10 dBm, which is in range.

    A 3dB attenuator in line will drop the signal to 10 dBm as well.

    I've built lots of systems like that. The 10 MHz reference is
    delivered to everybody at +13 dBm, and it is the receivers'
    responsibility to attenuate it to whatever they need.


    I've now measured the 100Mhz oscillator and that seems fine,
    although I only saw 0.61V p-p into 50 ohms, so somewhat less than
    the 10Mhz oscillator's output.
    So far, I've not measured anything which screams "the fault's
    here!" as all the expected signals are present - although
    admittedly I have many more to test. But certainly all the *major* >>>>>> signals within this complex beast are present. It's looking like it >>>>>> could be an issue with one of the phase detectors or LPFs. Sigh.... >>>>>
    To my eye, it does scream.

    Joe Gwinn

    Joe, I appreciate you're only trying to help, but don't worry about it.
    I don't believe the oscillator this thread relates to is causing the
    PLL unlock error so we've all gone down a bit of a rabbit hole with
    this one.
    I really need to look elsewhere for the culprit.

    For what it's worth, I found a manual on the web saying that the 10MHz
    output should deliver +5dBm into 50 Ohms. It's a bit low, then, but I
    doubt that this is your problem.

    Jeroen Belleman

    Thanks, Jeroen. It would be a pretty simple matter to provide the analyzer
    with an external 10Mhz source of that level from an RF signal generator,
    but as we've both said now, I don't think that's the issue.
    The service manual only says to investigate boards A19,A20,A21 and A11 -
    which I have done superficially. But I've just noticed in the Repair & Troubleshooting manual it says A16 should also be checked, so I'll do that next.....
    Many thanks.

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  • From Cursitor Doom@21:1/5 to John R Walliker on Wed Jun 5 17:09:31 2024
    On Mon, 3 Jun 2024 22:44:19 +0100, John R Walliker wrote:

    On 02/06/2024 13:12, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 13:00:21 +0100, John R Walliker wrote:

    On 02/06/2024 12:31, Cursitor Doom wrote:
    On Sun, 2 Jun 2024 11:17:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

    Cursitor Doom <cd999666@notformail.com> wrote:
    On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:

    On 6/1/24 14:07, Cursitor Doom wrote:

    I've taken a shot of the waveform into the 50 ohm input. It's >>>>>>>>>> around 850mV peak-peak. Hopefully the slight distortion I spoke >>>>>>>>>> about is visible; the slightly more leisurely negative-going >>>>>>>>>> excursions WRT their positive-going counterparts. So it's not a >>>>>>>>>> pure sine wave as one would expect. Does it matter? I don't >>>>>>>>>> know!

    https://disk.yandex.com/i/7cuuBimDbOIBZw

    The shape looks perfectly acceptable to me. This is +3dBm into >>>>>>>>> 50 Ohms.
    Is that what it's supposed to be? Canned reference oscillators >>>>>>>>> most often deliver +13dBm, sometimes +10dBm.

    Is it? I only make it about half your figure: +1.65dBm.
    I admit I'm frequently prone to careless errors, so stand to be >>>>>>>> corrected,
    but here's my method:
    850mV peak to peak is 425mV peak voltage. Average of that is
    0.425x0.636 =
    0.27V. Average power is average volts squared divided by the load >>>>>>>> impedance of 50 ohms = 1.46mW = +1.65dBm.

    I shall consult the manual to see what it ought to be - if I can >>>>>>>> find it, that is, as PDF manuals are a nightmare to navigate IME. >>>>>>>>


    Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
    +2.6dBm ?

    Thanks, Erich. But there's no such thing as "RMS power" strictly
    speaking IIRC, so that's why I took the average figure; not that it >>>>>> makes much difference in practice. it does seem a bit on the low
    side, but despite reading through the most likely sources (the
    service manual and the trouble-shooting/repair manual) I can find
    nothing stated for what that signal level should be! This may be
    due to the user-unfriendliness of very large PDF manuals; I just
    don't know. Anyway, not very satisfactory! Later today I plan to do >>>>>> a direct power meter measurement of the ref osc (since none of us
    here seem to agree on what 850mV vs 50 ohms equates to!!)





    Since you have a power meter, a signal source, and an oscilloscope
    why not measure the peak to peak voltage on the scope and power on
    the power meter and see which calculation 0.636 vs 0.707 gives the
    closest agreement?

    It wouldn't prove anything one way or ther other, though, since that
    power meter hasn't been calibrated for "quite a while" so to speak.
    :)
    It'll give a 'good enough' reading for my purposes, but won't be
    accurate enough to meaningfully test your otherwise fine suggestion.

    I have an 8566B which is currently not working. Both the status leds
    on the front panel at the bottom are red. I haven't started to
    investigate yet.
    The fault developed slowly. At first it would sometimes work, then
    progressively less often and now never.
    However, if the signal being discussed is available on the rear panel
    I could measure mine and see what it looks like and what voltage is
    delivered.
    John

    Yes, that could be very helpful, John, since your fault is clearly
    totally different to mine. Peak to peak volts into 50 ohms on a scope
    will be fine if don't have access to an RF power meter.

    I measured the 10MHz output of my unit with an HP 54542A digital storage 'scope and found the following:
    1Mohm input via 5m coax 1.133 Vp-p 405.8 mVrms

    50ohm input via 5m coax 790.3 mVp-p 284.9 mVrms

    The waveform with 1Mohm load looked like a perfect sine wave, whereas
    the 50 ohm loaded waveform showed some second harmonic distortion
    visible as a slight narrowing of the top of the sine and a slight
    flattening of the bottom of the sine.

    The frequency measured with an HP 53131A frequency counter was
    10.000199MHz.
    The spectrum analyzer had been on standby for a few weeks and fully
    powered for a few hours, so the crystal oven should have been at
    equilibrium. I then substituted my rubidium oscillator which indicated 9.999997MHz on the counter.

    The connector that I used was the one labelled 10MHz at bottom right,
    not the adjacent reference output which is connected to a reference
    input with a short coax jumper. Is the same output that you measured?

    John

    Hi John, sorry for the delay in replying.
    You got some interesting results there. Not what I'd expected, to be
    honest. We have to bear in mind that the 8566B is a different beast to
    yours, of course, so a bit of leeway can be allowed for that.
    Nevertheless, the fact you're getting a decent sine wave into 1Meg is
    curious, given what I experienced. I'm taking my 10Mhz from a BNC socket
    on the rear panel which HP placed there to make it easier to check and
    adjust the 10.0000000Mhz out as precisely as possible. I'm sure yours
    *will* be different, but that shouldn't matter. I also got the same
    results by popping off one of the 50 ohm interconnects from the board the
    A22 10Mhz ref feeds into.
    Thanks for including the p-p voltage figures in your report; helps a lot.
    Many thanks again.

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