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HP 8566B - What to look for?
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KE5FX:
You're set to 1 dB/division, so you can't see anything but the peak.  Try these settings:



(from 27xx serial #)
G0HZU:
Thanks! The plot I posted up is taken from the B manual but it is a reprint from the A manual. It looks like the loop response is different on the later models. Close in phase noise is better but the phase noise at 50kHz offset is higher.
Quite surprisingly, my analyser still uses the same loop response on a 50kHz span and this really doesn't look good. Maybe there is a way to upgrade it to emulate the later versions. However, that is a topic for another day...


--- Quote ---My pleasure! Is this what you are looking for? Or did I miss a step?
--- End quote ---
Can you set it to 10dB/div as shown by KE5FX. I think you will then see a similar plot as the one from KE5FX's analyser.
G0HZU:
If you have access to a VNA (even a nanovna) that can cover up to 3GHz or higher, then you should be able to connect the VNA to the input port of the 8566B and then set the 8566B to (say) 2.7GHz on a 1MHz span and then set the input attenuator to 0dB. Then set the VNA to an s11 measurement. Set the VNA source power to -10dBm or less.

You should then be able to see a dip in the return loss at 2.7GHz if the YIG preselector is working and tracking correctly. It should show a return loss of >10dB across about a 20MHz? bandwidth (at a guess).

It is then also possible to press 'SHIFT' 'GHZ' and this should bring up an oncreen YIG DAC control feature. You can rotate the wheel on the front panel of the 8566B and then the YIG filter frequency can be tuned over a limited frequency range either side of 2.7GHz.

This should give an indication of the health of the YIG spheres and also the YIG tuning and control sections without having to take anything apart inside the analyser.

If you don't have a VNA then maybe make or borrow a directional coupler and use it with your Anritsu analyser + tracking gen to do the same thing.
W4PJB:

--- Quote from: G0HZU on June 22, 2024, 10:49:24 am ---If you have access to a VNA (even a nanovna) that can cover up to 3GHz or higher, then you should be able to connect the VNA to the input port of the 8566B and then set the 8566B to (say) 2.7GHz on a 1MHz span and then set the input attenuator to 0dB. Then set the VNA to an s11 measurement. Set the VNA source power to -10dBm or less.



--- End quote ---

A 3 GHz VNA... funny you should mention that :D

Thank you for your advice!
W4PJB:

--- Quote from: G0HZU on June 22, 2024, 10:42:14 am ---Thanks! The plot I posted up is taken from the B manual but it is a reprint from the A manual. It looks like the loop response is different on the later models. Close in phase noise is better but the phase noise at 50kHz offset is higher.
Quite surprisingly, my analyser still uses the same loop response on a 50kHz span and this really doesn't look good. Maybe there is a way to upgrade it to emulate the later versions. However, that is a topic for another day...


--- Quote ---My pleasure! Is this what you are looking for? Or did I miss a step?
--- End quote ---
Can you set it to 10dB/div as shown by KE5FX. I think you will then see a similar plot as the one from KE5FX's analyser.

--- End quote ---

Here you go! Sorry about the first go-around; my unit is butterflied out on my bench right now, so everything is either upside down, sideways, or both, depending on how I crane my neck to see anything.
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