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
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
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.
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
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. :)
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. :)
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
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. :)
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.
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.
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
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. :)
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.
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
On 2024-05-29 18:59, Joe Gwinn wrote:
On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil HobbsYeah, or an emitter follower. Good point.
<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: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
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. >>>>
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
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 HobbsYeah, or an emitter follower. Good point.
<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:I don't understand how a reflection can account for it either. THe cable's
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. >>>>>
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
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
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 HobbsYeah, or an emitter follower. Good point.
<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:I don't understand how a reflection can account for it either. THe cable's
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. >>>>>>
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
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?
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 HobbsYeah, or an emitter follower. Good point.
<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>I don't understand how a reflection can account for it either. THe cable's
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. >>>>>>>
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
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
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 HobbsYeah, or an emitter follower. Good point.
<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
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.
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 HobbsYeah, or an emitter follower. Good point.
<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
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
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 HobbsYeah, or an emitter follower. Good point.
<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
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
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 HobbsYeah, or an emitter follower. Good point.
<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
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.
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 HobbsYeah, or an emitter follower. Good point.
<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
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.
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>
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
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
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>
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
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
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>
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
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.
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>
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
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!
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>>
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
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
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 HobbsYeah, or an emitter follower. Good point.
<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
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 (DCHere, I meant even harmonic(s) not just second harmonic.
offset bascially)
It's rather hot today in Phoenix..
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>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>
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:Yeah, or an emitter follower. Good point.
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
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/
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 (DCHere, I meant even harmonic(s) not just second harmonic.
offset bascially)
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
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.
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>
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
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.
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>>
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
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.
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 HobbsYeah, or an emitter follower. Good point.
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Cursitor Doom <cd999666@notformail.com> wrote:
On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: >>>>>>>>>>>>>>That?s pretty diagnostic. There must be an LC filter on the >>>>>>>>>>>>> output?mis-terminating it will cause all sorts of
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. :) >>>>>>>>>>>>>
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
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!)
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:Yeah, or an emitter follower. Good point.
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
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
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.
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:Yeah, or an emitter follower. Good point.
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
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.
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 ?
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?
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.
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:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?
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.
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!!)
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.
On 6/2/24 00:24, piglet wrote:
piglet <erichpwagner@hotmail.com> wrote:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm
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.
?
rather than the 0.85v figure of your message.
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?
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:Since you have a power meter, a signal source, and an oscilloscope why
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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.
+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!!)
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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:Since you have a power meter, a signal source, and an oscilloscope why
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm
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.
?
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!!)
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?
Peak to peak volts into 50 ohms on a scope will be fine
if don't have access to an RF power meter.
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:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?
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.
rather than the 0.85v figure of your message.
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/
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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sun, 2 Jun 2024 13:49:16 +0200, Jeroen Belleman wrote:It’s really not this hard.
On 6/2/24 00:24, piglet wrote:
piglet <erichpwagner@hotmail.com> wrote:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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.
+2.6dBm ?
rather than the 0.85v figure of your message.
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/
“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
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:Since you have a power meter, a signal source, and an oscilloscope why
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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.
+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!!)
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.B07MP9D9GC?th=1>
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/
Just buying a few of these and doing some experiments will be far
cheaper and faster than the various alternatives discussed.t
Joe Gwinn
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:Since you have a power meter, a signal source, and an oscilloscope why
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?
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.
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!!)
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.
On Wed, 29 May 2024 20:49:27 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:e
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.
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:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>> ?
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.
rather than the 0.85v figure of your message.
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/
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: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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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. >>>>>>>
+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!!)
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....
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:Since you have a power meter, a signal source, and an oscilloscope why
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>> ?
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.
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!!)
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
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:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope pic
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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.
+2.6dBm ?
rather than the 0.85v figure of your message.
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
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: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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>> ?
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.
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!!)
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.
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:Since you have a power meter, a signal source, and an oscilloscope
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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. >>>>>>>>
+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!!)
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
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: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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>>> ?
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.
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!!)
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
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:To CD:
Cursitor Doom <cd999666@notformail.com> wrote: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.
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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. >>>>>>>
+2.6dBm ?
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!
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:To CD:
Cursitor Doom <cd999666@notformail.com> wrote:Or +2.9dBm if using the 0.88v pk-pk I think is shown in the scope
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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. >>>>>>>>
+2.6dBm ?
pic rather than the 0.85v figure of your message.
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
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: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
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm >>>>>>>> ?
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. >>>>>>>>>
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!!)
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.
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>
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?Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>> +2.6dBm ?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. >>>>>>>>>
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!!)
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
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:And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>
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>
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?Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>> +2.6dBm ?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.
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!!)
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
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:And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>
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>
B07MP9D9GC?th=1>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?Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>>> +2.6dBm ?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.
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!!)
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/
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.
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:And <https://disk.yandex.com/i/z6fYbeVfPRK7aA>
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>
B07MP9D9GC?th=1>Since you have a power meter, a signal source, and anUse 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or >>>>>>>>>>> +2.6dBm ?The shape looks perfectly acceptable to me. This is +3dBm >>>>>>>>>>>>> into 50 Ohms.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,
Is that what it's supposed to be? Canned reference
oscillators most often deliver +13dBm, sometimes +10dBm. >>>>>>>>>>>>
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.
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!!)
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/
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,To my eye, it does scream.
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.... >>>>>
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
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:Since you have a power meter, a signal source, and an oscilloscope
Cursitor Doom <cd999666@notformail.com> wrote:
On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or
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. >>>>>>>>
+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!!)
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
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