Re: HP 8753D In Circuit Calibration
Dr Kirkby,
Quite true, of course.? I was aiming to verify that the cal kit constants assumed "near perfect" standards.? If the cal kit assumes offset short and open then measuring a non-offset short or open will not appear as a small point at the left or right of the Smith chart.
--John Gord
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On Fri, Oct 25, 2024 at 03:28 PM, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
The 8753D 7mm cal kit setting assumes nearly perfect standards.? As I remember, only the open has any corrections, and that is something like 90fF of fringing capacitance.?
If you select the 7mm kit and then calibrate at the solder end of your pigtails with a 50ohm SMD resistor, a "short" short and a "short" open, you should get decent results.? Verify by measuring your short, open, and load after calibration to see if you get the results you expect.? Try to keep the leads at the end of your pigtail very short.
--John Gord
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Measuring the standards use to perform a calibration will not provide any verification. If a 10 ohm resistor was used during calibration, it will read 50 ohms on the VNA.?
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Re: HP 8753D In Circuit Calibration
I use a length of semirigid coax to insert into small places and on small SMT PCBs.? ? Made reasonably good measurements to and maybe beyond 500 MHz this way.? ??
I found a length of this coax with SMA or SMB connectors on each end and removed one of them to expose the center conductor which is made of silver plated steel.? This is the probe tip.? For the ground side I lash a a gold plated brass header pin to the outer conductor using fine wire and carefully solder it to get a secure rigid ground pin.? ?This creates a small useful probe that can get across surface mount components or to just get in a small point on a circuit board trace.? ? ?To perform an open-short-load calibration:? I solder a pair of 100 ohm resistors on top of each other with one leg of the parallel-connected stack on a PCB ground plane and the other end floating so I can get a secure and repeatable connection to the 50 ohm stack.? For a short, I scratch the center pin and the ground pin along the ground plane copper on the same PCB (with the 50 ohm stack for convenience).? ?The scratch marks indicate that I am getting a good connection for the short part of the cal.? ?For an open I simply leave the little fork open.? ?
I used this for years on SMT PCBs as a product support engineer (worked on product improvements after intro to the factory and during production when test results were not trending the right direction etc..).? ?I know the results were decent because impedance data from the measurements made using this method when applied in circuit simulation program (ADS ) and after implementation, performance was improved with reliable outcomes.? ?The products were mil radios so we tested very thoroughly after any change no matter how insignificant the change was made.? ? ? ? ??
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Re: HP 8753D In Circuit Calibration
The 8753D 7mm cal kit setting assumes nearly perfect standards.? As I remember, only the open has any corrections, and that is something like 90fF of fringing capacitance.?
If you select the 7mm kit and then calibrate at the solder end of your pigtails with a 50ohm SMD resistor, a "short" short and a "short" open, you should get decent results.? Verify by measuring your short, open, and load after calibration to see if you get the results you expect.? Try to keep the leads at the end of your pigtail very short.
--John Gord
Measuring the standards use to perform a calibration will not provide any verification. If a 10 ohm resistor was used during calibration, it will read 50 ohms on the VNA.?
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I have a 16702A that worked fine when I put it on the shelf a couple
years ago. Pulled it out the other day for a project and the LCD
is glitchy. There's random jitter and sometimes lines shoot through
the display. Plain text, before X takes over, can be almost unreadable.
Display on an external monitor is fine.
Anyone else see this problem? I normally use a remote display so this
doesn't impact my project, but it is annoying.
Paul
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Linux/Unix - We don't do windows
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Re: HP 8753D In Circuit Calibration
The 8753D 7mm cal kit setting assumes nearly perfect standards.? As I remember, only the open has any corrections, and that is something like 90fF of fringing capacitance.?
If you select the 7mm kit and then calibrate at the solder end of your pigtails with a 50ohm SMD resistor, a "short" short and a "short" open, you should get decent results.? Verify by measuring your short, open, and load after calibration to see if you get the results you expect.? Try to keep the leads at the end of your pigtail very short.
--John Gord
?
On Fri, Oct 25, 2024 at 01:40 PM, <fpgadaemon@...> wrote:
I'm trying to measure S21 of a filter on a PCB. Due to space restrictions, I am unable to connect SMA connectors for measurement, instead I'm looking to solder pigtails to appropriate points. However, I'm unsure as to what my calibration approach should be?
?
I vaguely recall seeing somewhere that it is possible to calibrate by soldering appropriate short/50R in/out of the circuit - not extremely accurate, but perhaps better than nothing. However, when I'm looking to perform a cal on my 8753D, it seems like it always wants to apply coefficients from 'proper' cal kits. To what extent will these affect the above cal approach?
?
I've tried searching the manual and online, but can't seem to find an accessible source going through good practice. If anyone can provide refs to app notes and/or the appropriate section of the 8753D manual, I would be very grateful.
?
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Re: HP 8753D In Circuit Calibration
Thank you both for your replies.
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I should say I am measuring at 2.4GHz, so will try the port extension method.
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Re: HP 8753D In Circuit Calibration
At probably <3 GHz, port extension will work fine.? > 20 GHz, no way.? Depends on your frequency range of interest.? ?HTH.? Jim Ford, Laguna Hills, California, USA (but vacationing in Mexico at the moment)
On Fri, Oct 25, 2024 at 1:48 PM, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote: On Fri, Oct 25, 2024 at 01:40 PM, <fpgadaemon@...> wrote:
I'm trying to measure S21 of a filter on a PCB. Due to space restrictions, I am unable to connect SMA connectors for measurement, instead I'm looking to solder pigtails to appropriate points. However, I'm unsure as to what my calibration approach should be?
?
I vaguely recall seeing somewhere that it is possible to calibrate by soldering appropriate short/50R in/out of the circuit - not extremely accurate, but perhaps better than nothing. However, when I'm looking to perform a cal on my 8753D, it seems like it always wants to apply coefficients from 'proper' cal kits. To what extent will these affect the above cal approach?
?
I've tried searching the manual and online, but can't seem to find an accessible source going through good practice. If anyone can provide refs to app notes and/or the appropriate section of the 8753D manual, I would be very grateful.
?
An approach which will get you somewhere near correct is to perform a calibration with SMA, attach your pigtails, then apply a short where you want to measure.
?
CAL >> Port Extensions (turn on), adjust port 1 or port 2.
?
Then look at the phase of the short. An ideal short will be 18i0 degrees. Add a port extension to bring that phase to 180 degrees at the frequency of interest. It should be flat with frequency if the transmission line is ideal, which it will not be. Make sure the port extension in mm looks about right, considering the length of the cable and velocity factor.
?
?
Dave
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Re: HP 8753D In Circuit Calibration
On Fri, Oct 25, 2024 at 01:40 PM, <fpgadaemon@...> wrote:
I'm trying to measure S21 of a filter on a PCB. Due to space restrictions, I am unable to connect SMA connectors for measurement, instead I'm looking to solder pigtails to appropriate points. However, I'm unsure as to what my calibration approach should be?
?
I vaguely recall seeing somewhere that it is possible to calibrate by soldering appropriate short/50R in/out of the circuit - not extremely accurate, but perhaps better than nothing. However, when I'm looking to perform a cal on my 8753D, it seems like it always wants to apply coefficients from 'proper' cal kits. To what extent will these affect the above cal approach?
?
I've tried searching the manual and online, but can't seem to find an accessible source going through good practice. If anyone can provide refs to app notes and/or the appropriate section of the 8753D manual, I would be very grateful.
?
An approach which will get you somewhere near correct is to perform a calibration with SMA, attach your pigtails, then apply a short where you want to measure.
?
CAL >> Port Extensions (turn on), adjust port 1 or port 2.
?
Then look at the phase of the short. An ideal short will be 18i0 degrees. Add a port extension to bring that phase to 180 degrees at the frequency of interest. It should be flat with frequency if the transmission line is ideal, which it will not be. Make sure the port extension in mm looks about right, considering the length of the cable and velocity factor.
?
?
Dave
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HP 8753D In Circuit Calibration
I'm trying to measure S21 of a filter on a PCB. Due to space restrictions, I am unable to connect SMA connectors for measurement, instead I'm looking to solder pigtails to appropriate points. However, I'm unsure as to what my calibration approach should be?
?
I vaguely recall seeing somewhere that it is possible to calibrate by soldering appropriate short/50R in/out of the circuit - not extremely accurate, but perhaps better than nothing. However, when I'm looking to perform a cal on my 8753D, it seems like it always wants to apply coefficients from 'proper' cal kits. To what extent will these affect the above cal approach?
?
I've tried searching the manual and online, but can't seem to find an accessible source going through good practice. If anyone can provide refs to app notes and/or the appropriate section of the 8753D manual, I would be very grateful.
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HP1000F system to give away.
My Swiss high altitude lab was many years ago using two HP1000F computers. These were shipped to a computer museum in Lausanne but we kept a functional system in Li¨¨ge (Belgium) where my university is located. The idea was to have a minimum system able to read the tapes on which we saved the atmospheric spectra observed at the lab in case we missed something.?
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Now, I am close to retirement and all tapes have probably been transferred on modern media so this HP1000F system located in Li¨¨ge is not useful anymore and I would like to avoid an ill fate to this nice piece of equipment and find for it a nice home with a caring HP lover. Seeing it sent to metal recyclers or digested for its gold looks terrible.
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The system is made of a HP1000F CPU unit, 2 Kennedy 9000 tape units, 1 Kennedy 9218 Format Unit, 1 HP7912 Disk drive unit(rack version).
I don't know much more about the details except that I believe all was functional at the time when it was stocked. So I imagine that everything needed to link the units is probably there and perhaps connected. I didn't look but I suppose there is the necessary documentation lying around.
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Please send a PM if you are interested and have the resources to remove the units from the racks and transport them.
Don't forget any of these units except the formatter are in the 50-70 Kg range and the 5 units fill two racks. I did not have access to the back to give more info.
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Please also feel free to transfer this text to somebody you know who could fit the goal of this message. Since I have been a member of this group for many years, I know for sure that it is more lab oriented than computing.
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Christian.
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Re: HP 8657B af generator problem
thanks for your help ! In fact, it s not a very serious problem !? its not very important !
tanks again for your help, I will check all the other parameters before closing it !
have a good day
jacques
Be happy if that's the only problem. RF/microwave synthesizers usually focus on the precision and phase noise of the main carrier frequency, while the various modulation functions are of secondary importance.
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Ed.
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Re: HP8753B VNA question regarding if I purchase one
Hello, I don¡¯t know the rules offhand for trading on this forum, but if you want some APC-7 to SMA adapters private message me. I have a few I can sell at a price I am sure we can agree on. Gary WA2OMY ? ?
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From: [email protected] <[email protected]> On Behalf Of G H via groups.io
Sent: Thursday, October 24, 2024 7:37 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP8753B VNA question regarding if I purchase one? Well Gang, Here is some followup for all to read. I went ahead and purchased some units. I have a HP8753C coming sometime next week. It comes with option 10. I also purchased a HP85047A test set, (going to 6GHz). Also coming next week. I contacted the source on Kirkby Microwave Ltd on how to enable options 002 and 006 and received a reply, with the necessary info. So all I need now is the connection cables between the two units. Some APC-7 to SMA adapters, and SOLT terminations. The group is correct in advising me regarding costs. Looks like I will be eating a lot of peanut butter jelly sandwiches here in the future. So thanks for all the information that has been passed on, regarding this topic. I hope this helps someone else down the road on their decision process, regarding VNAs.
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Re: HP8753B VNA question regarding if I purchase one
So all I need now is the connection cables between the two units. Some APC-7 to SMA adapters, and SOLT terminations.
? The 4 coaxial cables are trivial to make. They don't need to be phase matched, but you don't want to use really poor cable that leaks like a sieve. Aesthetically it looks better if all 4 are the same length, but that's all you need to worry about.
IIRC there's a 25 pin DIN cable that corrects the test set to the VNA. But make sure you have one with all the conductors connected, as some of the cheap ones probably only have enough to get a printer to work.
Some test sets have a mechanical switch, and others electronic. I'll add some information about that on my site when I have a bit of time.
-- Dr David Kirkby Ph.D Kirkby Microwave Ltd Email: drkirkby@... Web: Telephone 07910 441670 (UK) or +44 7910 441670 (international) Registered in England and Wales, company number 08914892.? Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT
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Re: HP 8657B af generator problem
Be happy if that's the only problem. RF/microwave synthesizers usually focus on the precision and phase noise of the main carrier frequency, while the various modulation functions are of secondary importance.
?
Ed.
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Re: HP 8657B af generator problem
You have no adjustment for both frequencies, and only one common adjustment for the output level. ? ? 
? Yves ? hi all! I'm looking for help for a problem with my 8657B.
AF generator is slightly low on 1khz (997hz) 400hz is perfect ! I cant find the adjustment in servicing manual. ? I adjusted the oscillator to 0.707 vac. I can't find a way to calibrate my 1khz? thank you for your HELP AND HAVE A GOOD DAY JACQUES
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Re: HP 8657B af generator problem
Hi Jacques,
As Dan mentioned, the manual says that the allowable frequency error
is +/-2%, so your unit is well within spec.
A quick look at the schematic doesn't show any adjustments. The
frequency is set by the RC values of the bridged-T feedback network
around U21A. If a 0.3% error is important to you for reasons other
than "a measurable error bugs me", post back. Otherwise, I'd just
leave well enough alone.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 10/24/2024 7:07 PM, jack wrote:
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hi all! I'm looking for help for a problem with my 8657B.
AF generator is slightly low on 1khz (997hz) 400hz is perfect ! I cant find the adjustment in servicing manual.
I adjusted the oscillator to 0.707 vac. I can't find a way to calibrate my 1khz? thank you for your HELP AND HAVE A GOOD DAY
JACQUES
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Re: HP 8657B af generator
Hi, ? Hi, I guess you mean the MOD in/out, in my case I get: @1kHz => 997.2Hz and 0.996Vpeak. @400Hz => 398.1Hz and 0.996Vpeak. ? The frequency is specified at ¡À2% with 997Hz, you have -0.3% For the level it is 1Vpeak, it is ¡À5%, that is from .995Vpeak to 1.05Vpeak. ? Yves ? ? Good morning ! hp 8657b the problem is that the AF generator is slightly low at 1k 997Hz I can't find the AF adjustment in the manual I have 2 volts on the audio board, I adjusted the oscillator to 0.707 v. the 400hz is perfect, the 1kz remains to be adjusted! thank you for your help
jack
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Re: HP 8657B af generator problem
On 10/24/2024 7:07 PM, jack wrote:
hi all! I'm looking for help for a problem with my 8657B.
AF generator is slightly low on 1khz (997hz) 400hz is perfect !
It is not a problem Jacques, apart from the fact it is specified
to +/- 2% so it is in spec, in practice it wouldn't make
any difference.
Dan
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Good morning ! hp 8657b
the problem is that the AF generator is slightly low at 1k 997Hz
I can't find the AF adjustment in the manual
I have 2 volts on the audio board, I adjusted the oscillator to 0.707 v. the 400hz is perfect, the 1kz remains to be adjusted!
thank you for your help
jack
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HP 8657B af generator problem
hi all! I'm looking for help for a problem with my 8657B.
AF generator is slightly low on 1khz (997hz) 400hz is perfect ! I cant find the adjustment in servicing manual.
I adjusted the oscillator to 0.707 vac. I can't find a way to calibrate my 1khz? thank you for your HELP AND HAVE A GOOD DAY
JACQUES
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Dr. David Kirkby, Kirkby Microwave Ltd