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  • Minicircuits ZFL-500 directivity question

    From bitrex@21:1/5 to All on Sat Nov 4 16:55:01 2023
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12| then something seems wrong with my setup and/or
    the amp.

    Doing the measurements on a (unfortunately not my personal home-lab
    machine!) Keysight 5080.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to bitrex on Sat Nov 4 16:59:33 2023
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12|

    Or rather |S12| - |S21|

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John May@21:1/5 to bitrex on Sat Nov 4 15:01:11 2023
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec but if it's |S21 - S12|
    Or rather |S12| - |S21|

    It's just the difference in dB, from the datasheet s21 is about 25dB, directivity about 38db, so s12 is 38dB below s21, or -13dB.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John May@21:1/5 to John May on Sat Nov 4 15:34:08 2023
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote:
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks? Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to John May on Sun Nov 5 17:18:12 2023
    On 11/4/2023 6:34 PM, John May wrote:
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote:
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something >>>> dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec >>>> but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB

    Thanks for your reply but I don't quite follow - do you know how they
    calculate the ~40dB figures of the top table on page 2?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John May@21:1/5 to bitrex on Sun Nov 5 16:53:16 2023
    On Sunday, November 5, 2023 at 10:18:21 PM UTC, bitrex wrote:
    On 11/4/2023 6:34 PM, John May wrote:
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote:
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB
    Thanks for your reply but I don't quite follow - do you know how they calculate the ~40dB figures of the top table on page 2?

    It is just the magnitude of the amplifier isolation (reverse gain) minus the (forward) gain. If reverse gain was -80dB and forward gain 20dB direcivity would be 60dB.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to John May on Sun Nov 5 22:58:36 2023
    On 11/5/2023 7:53 PM, John May wrote:
    On Sunday, November 5, 2023 at 10:18:21 PM UTC, bitrex wrote:
    On 11/4/2023 6:34 PM, John May wrote:
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote:
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something >>>>>> dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec >>>>>> but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB
    Thanks for your reply but I don't quite follow - do you know how they
    calculate the ~40dB figures of the top table on page 2?

    It is just the magnitude of the amplifier isolation (reverse gain) minus the (forward) gain. If reverse gain was -80dB and forward gain 20dB direcivity would be 60dB.

    Gotcha, thanks!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to bitrex on Mon Nov 6 13:25:32 2023
    bitrex <user@example.net> wrote:
    On 11/5/2023 7:53 PM, John May wrote:
    On Sunday, November 5, 2023 at 10:18:21 PM UTC, bitrex wrote:
    On 11/4/2023 6:34 PM, John May wrote:
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote:
    On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks? >>>>>>> Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> >>>>>>>
    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, >>>>> directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB
    Thanks for your reply but I don't quite follow - do you know how they
    calculate the ~40dB figures of the top table on page 2?

    It is just the magnitude of the amplifier isolation (reverse gain) minus
    the (forward) gain. If reverse gain was -80dB and forward gain 20dB
    direcivity would be 60dB.

    Gotcha, thanks!


    Isolation is 1/(reverse gain), and it’s a straight subtraction, so 60 dB is correct for the wrong reason.

    One way of keeping it straight is that an N-dB pad has 2N dB isolation.
    (Using the magnitude would predict an isolation of 0 dB.) The idea is to
    say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs

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

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to Phil Hobbs on Mon Nov 6 11:24:47 2023
    On 11/6/2023 8:25 AM, Phil Hobbs wrote:
    bitrex <user@example.net> wrote:
    On 11/5/2023 7:53 PM, John May wrote:
    On Sunday, November 5, 2023 at 10:18:21 PM UTC, bitrex wrote:
    On 11/4/2023 6:34 PM, John May wrote:
    On Saturday, November 4, 2023 at 10:01:15 PM UTC, John May wrote: >>>>>> On Saturday, November 4, 2023 at 8:59:41 PM UTC, bitrex wrote:
    On 11/4/2023 4:55 PM, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks? >>>>>>>> Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> >>>>>>>>
    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12|
    Or rather |S12| - |S21|
    It's just the difference in dB, from the datasheet s21 is about 25dB, >>>>>> directivity about 38db, so s12 is 38dB below s21, or -13dB.

    That's wrong - would be -(25+38)dB
    Thanks for your reply but I don't quite follow - do you know how they
    calculate the ~40dB figures of the top table on page 2?

    It is just the magnitude of the amplifier isolation (reverse gain) minus >>> the (forward) gain. If reverse gain was -80dB and forward gain 20dB
    direcivity would be 60dB.

    Gotcha, thanks!


    Isolation is 1/(reverse gain), and it’s a straight subtraction, so 60 dB is correct for the wrong reason.

    One way of keeping it straight is that an N-dB pad has 2N dB isolation. (Using the magnitude would predict an isolation of 0 dB.) The idea is to
    say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs





    Thank you, so just S21 - S12? S21 for the ZFL-500 was about 20 dB and
    S21 -40, that would seem to imply 60 dB directivity while the spec says
    around 40 in the mid band, seems hard to believe it's beating the spec
    by that much.

    But I'm unsure how much input power affects this, does the datasheet
    table imply these measurements are taken at the 1dB compression point?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to bitrex on Mon Nov 6 11:25:29 2023
    On 11/6/2023 11:24 AM, bitrex wrote:

    One way of keeping it straight is that an N-dB pad has 2N dB isolation.
    (Using the magnitude would predict an isolation of 0 dB.)  The idea is to >> say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs





    Thank you, so just S21 - S12? S21 for the ZFL-500 was about 20 dB and
    S21 -40

    Sorry S12 was about -40, rather

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to bitrex on Mon Nov 6 11:32:07 2023
    On 11/6/2023 11:24 AM, bitrex wrote:

    Isolation is 1/(reverse gain), and it’s a straight subtraction, so 60
    dB is
    correct for the wrong reason.

    One way of keeping it straight is that an N-dB pad has 2N dB isolation.
    (Using the magnitude would predict an isolation of 0 dB.)  The idea is to >> say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs





    Thank you, so just S21 - S12?
    To clarify I mean the log magnitudes here, as a VNA so conveniently can
    display for us

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to bitrex on Mon Nov 6 19:05:45 2023
    bitrex <user@example.net> wrote:
    On 11/6/2023 11:24 AM, bitrex wrote:

    One way of keeping it straight is that an N-dB pad has 2N dB isolation.
    (Using the magnitude would predict an isolation of 0 dB.)  The idea is to >>> say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs





    Thank you, so just S21 - S12? S21 for the ZFL-500 was about 20 dB and
    S21 -40

    Sorry S12 was about -40, rather


    A reverse gain of-40 dB is an isolation of +40 dB, so the directivity is
    40-20 = 20 dB.

    If you put a short or open on the output, it will reflect the full output
    power back into the output port. That’s 20 dB above the input power, so assuming a matched input and 40 dB isolation, you’d get an input return
    loss of 20 dB. That’s what the directivity expresses.

    Cheers

    Phil Hobbs

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

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to Phil Hobbs on Mon Nov 6 16:36:14 2023
    On 11/6/2023 2:05 PM, Phil Hobbs wrote:
    bitrex <user@example.net> wrote:
    On 11/6/2023 11:24 AM, bitrex wrote:

    One way of keeping it straight is that an N-dB pad has 2N dB isolation. >>>> (Using the magnitude would predict an isolation of 0 dB.)  The idea is to >>>> say how much a mismatch affects the input impedance.

    Cheers

    Phil Hobbs





    Thank you, so just S21 - S12? S21 for the ZFL-500 was about 20 dB and
    S21 -40

    Sorry S12 was about -40, rather


    A reverse gain of-40 dB is an isolation of +40 dB, so the directivity is 40-20 = 20 dB.

    If you put a short or open on the output, it will reflect the full output power back into the output port. That’s 20 dB above the input power, so assuming a matched input and 40 dB isolation, you’d get an input return loss of 20 dB. That’s what the directivity expresses.

    Cheers

    Phil Hobbs


    I see why JL loves his time domain.

    The 5080 is a nice instrument, it seems to boot to Windows 7. Crashes to Windows 7, too..

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Simon S Aysdie@21:1/5 to Simon S Aysdie on Tue Nov 7 14:45:30 2023
    On Tuesday, November 7, 2023 at 2:42:48 PM UTC-8, Simon S Aysdie wrote:
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec but if it's |S21 - S12| then something seems wrong with my setup and/or the amp.

    Doing the measurements on a (unfortunately not my personal home-lab machine!) Keysight 5080.
    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002


    I should say:
    D = -|S12| (dB)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Simon S Aysdie@21:1/5 to bitrex on Tue Nov 7 14:42:44 2023
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12| then something seems wrong with my setup and/or
    the amp.

    Doing the measurements on a (unfortunately not my personal home-lab machine!) Keysight 5080.

    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to Simon S Aysdie on Wed Nov 8 11:11:31 2023
    On 11/7/2023 5:42 PM, Simon S Aysdie wrote:
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12| then something seems wrong with my setup and/or
    the amp.

    Doing the measurements on a (unfortunately not my personal home-lab
    machine!) Keysight 5080.

    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002

    Thanks Simon, yes that seems right, this amp was bang on within spec
    otherwise so I'd have been surprised if it was way off there.

    They're nice lil modules, I didn't have this purpose in mind but I
    wonder if they make a LNA suitable to replace the shit ass front end on
    my DTV antenna, I live in a fringe area so reception varies by the day.
    and I'm in a condo so mounting stuff outdoors not really feasible

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From bitrex@21:1/5 to Fred Bloggs on Wed Nov 8 13:12:02 2023
    On 11/8/2023 11:47 AM, Fred Bloggs wrote:
    On Wednesday, November 8, 2023 at 11:11:40 AM UTC-5, bitrex wrote:
    On 11/7/2023 5:42 PM, Simon S Aysdie wrote:
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something >>>> dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec >>>> but if it's |S21 - S12| then something seems wrong with my setup and/or >>>> the amp.

    Doing the measurements on a (unfortunately not my personal home-lab
    machine!) Keysight 5080.

    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002
    Thanks Simon, yes that seems right, this amp was bang on within spec
    otherwise so I'd have been surprised if it was way off there.

    They're nice lil modules, I didn't have this purpose in mind but I
    wonder if they make a LNA suitable to replace the shit ass front end on
    my DTV antenna, I live in a fringe area so reception varies by the day.
    and I'm in a condo so mounting stuff outdoors not really feasible

    Your reception is probably being degraded by suboptimal antenna pointing, the sun, and unpredictable multi-path signal impingement [ coastal is littoral causes no end of propagation anomalies ]. It doesn't cost the manufacturer anything to provide a
    high performance front end amplifier

    It doesn't?

    all of which intended for satellite reception are LN-A's. The
    customers pay for everything, do you think it's wise then for them to
    provide junk performance parts making customers into ex-customers?

    Could apply the same argument to many other industries...and conclude
    all products are high-quality because otherwise the manufacturer might
    lose customers.

    Hey, I have a cool idea, I'll see if I can put it on the 5080 next time
    I have a chance and see how it compares to a Minicircuits gain block for similar bandwidth, I think I can get a hold of one..

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From upsidedown@downunder.com@21:1/5 to bitrex on Thu Nov 9 00:02:39 2023
    On Wed, 8 Nov 2023 11:11:31 -0500, bitrex <user@example.net> wrote:

    They're nice lil modules, I didn't have this purpose in mind but I
    wonder if they make a LNA suitable to replace the shit ass front end on
    my DTV antenna, I live in a fringe area so reception varies by the day.
    and I'm in a condo so mounting stuff outdoors not really feasible

    That ZFL-500 is not very suitable as antenna amplifier for DTV. First
    of all it is quite noisy, noise figure NF = 4.2 dB (typical). These
    days a good antenna amplifier the NF should be below 3 dB. That
    amplifier is specified only up to 500 MHz, thus most UHF channels are
    out of range. However, it might still work since the specs are good at
    500 MHz, wonder why the specs ends at 500 MHz.

    An antenna amplifier should be installed _at_ the antenna, thus the
    cable between amplifier and DTV receiver can be long.

    You seem to suffer from tropospheric fading and the signal nulls can
    be quite deep and the signal is still momentary lost no matter what
    antenna amplifier you use. Only a proper outdoor antenna will really
    help.

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  • From bitrex@21:1/5 to upsidedown@downunder.com on Wed Nov 8 18:12:07 2023
    On 11/8/2023 5:02 PM, upsidedown@downunder.com wrote:
    On Wed, 8 Nov 2023 11:11:31 -0500, bitrex <user@example.net> wrote:

    They're nice lil modules, I didn't have this purpose in mind but I
    wonder if they make a LNA suitable to replace the shit ass front end on
    my DTV antenna, I live in a fringe area so reception varies by the day.
    and I'm in a condo so mounting stuff outdoors not really feasible

    That ZFL-500 is not very suitable as antenna amplifier for DTV. First
    of all it is quite noisy, noise figure NF = 4.2 dB (typical). These
    days a good antenna amplifier the NF should be below 3 dB. That
    amplifier is specified only up to 500 MHz, thus most UHF channels are
    out of range. However, it might still work since the specs are good at
    500 MHz, wonder why the specs ends at 500 MHz.

    Yeah it has gain for days. S21 is above 20dB well past 1 GHz.

    An antenna amplifier should be installed _at_ the antenna, thus the
    cable between amplifier and DTV receiver can be long.

    You seem to suffer from tropospheric fading and the signal nulls can
    be quite deep and the signal is still momentary lost no matter what
    antenna amplifier you use. Only a proper outdoor antenna will really
    help.

    I'll see if high pressure systems seem to make it better...atm with a
    planar antenna and associated amp I'm getting a station with a purported
    field strength of -70 dBm at 36 miles no problem if I kinda point it in
    that direction, but a station at 16 miles -50 dBm doesn't come in at all
    /shrug

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  • From Phil Hobbs@21:1/5 to Simon S Aysdie on Wed Nov 8 19:05:03 2023
    On 2023-11-07 17:45, Simon S Aysdie wrote:
    On Tuesday, November 7, 2023 at 2:42:48 PM UTC-8, Simon S Aysdie wrote:
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something >>> dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec >>> but if it's |S21 - S12| then something seems wrong with my setup and/or
    the amp.

    Doing the measurements on a (unfortunately not my personal home-lab
    machine!) Keysight 5080.
    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002


    I should say:
    D = -|S12| (dB)


    (Supernews doesn't seem to be registering my 3 PM EST reply just
    now--apologies for duplication if it shows up eventually.)

    It makes no sense to take the absolute value of a quantity expressed in decibels--that's saying that there's no difference between, say, a 100X
    voltage amp (+40 dB) and a 40-dB attenuator (-40 dB).

    The directivity is just |S12 * S21|, i.e. the effects at one port of a short-circuit load reflecting all of the signal backwards through the
    network. In decibels, it's

    D = 20 log(|S12 * S21|). Symmetrical. No big mystery.

    Cheers

    Phil Hobbs

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

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

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  • From Phil Hobbs@21:1/5 to Simon S Aysdie on Wed Nov 8 15:16:05 2023
    On 2023-11-07 17:42, Simon S Aysdie wrote:
    On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
    How is "directivity" defined for these Minicircuits gain blocks?
    Datasheet here:

    <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>

    Across the bandwidth of interest I'm measuring S21 as about 20-something
    dB give or take a dB which seems fine, S12 is at -40.

    If "directivity" in this context is just S12 then that seems within spec
    but if it's |S21 - S12| then something seems wrong with my setup and/or
    the amp.

    Doing the measurements on a (unfortunately not my personal home-lab
    machine!) Keysight 5080.

    They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you
    noted.

    Example:
    For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
    For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.

    Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

    !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
    # Hz S dB R 50
    100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002


    It isn't the absolute value in decibels. The directivity is just the
    magnitude of S21*S12. Otherwise you get the wrong answer for attenuators.

    Cheers

    Phil Hobbs

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

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

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