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I have an HP 8920A that I would like to run the Per-Cal proceedure on but I don't have a good description about how to do it. The manual says very little about what all the steps are. I have another calibrated HP8920A and a 10 MHZ GPSDO available. I understand the basic idea of what is happening but am unclear about how to do it. I would pay for a ZOOM session to get some instruction. Thanks!

I would suggest you first find a stable signal source that will allow you to map the warmup characteristics of your instrument over time.?
It is easier to get an idea from a signal at 500Mhz as opposed to a signal at 10Mhz.? You can try with internal vs your external ref.
It will be different depending on if you have the standard TCXO or the optional OCXO.? This will also give you an idea how long you
should wait for a warmup and what you might expect as a "before" calibration.? There is always some drift and there is a difference
between a TCXO at lab temp and the OCXO that must be heated up to temp.? You could beat your head against a wall over a few
Hertz if you don't understand it will be only that accurate if you always exactly duplicate the warmup time and ambient.? I have used
the ATSC pilot signal from off-air TV stations in saved screens for evaluating the warmup of the instrument.? Although they generally
don't have enough signal to meet the standard of PER_CAL function, they are a quick check.? My 8920a has an optional OCXO so
I have calibrated it after 2 hours warmup -+1 hz and I consider it ready after 30min for accurate -+10hz frequency readings.? I have
another IFR with a battery and a TCXO that I consider "ready enough" for -+20hz at 10 minutes.

There is also a manual adjustment that can be made that will be lost at reboot that can be used.? They input directly to the memory
positions for the coarse and fine adjustments of the ref-osc.? There is a sheet that tells of that adjustment on

Three documents of interest:
8920A-B-and-8921A-Test-Set-Assembly-Level-Repair-08920-90168.pdf???? File name may be abbreviated to the HP/Agilant # 08920-90168
The procedures, either manual or semi-automated from an external reference are on page 121.? It is very simple to do.? All you do is feed
a strong stable signal into the front input (rather than the REF input in the rear) that meets the minimum and follow the instructions on the
screen.? In the TESTS menu find Per_CAL.? It is I BASIC program that is included in the instrument.? You essentially run the program and
follow the directions.? If you screw up you can always do it again.

Also look in the FILES/HP-8920A and HP8920B related/ folder in this group and get:
08920-90126.pdf?? ??? Applications manual and-
8920A-RF-Communications-Test-Set-Users-Guide-(Apr00)-08920-90219.pdf ? the User manual.

There are several other documents there that might be of interest such as the "Quick User Guide".? It was included in the lid of unit and any
of the copies I have seen are kind of crude and low res but handy printed and put in a 3 ring binder.

Jim, you GPSDO is fine for this. I turn mine on for a day or 2 before I intend to use it. Most come from CDMA cell sites so have to lock pretty quick for power supply cuts and such.
I think PER_CAL also needed an accurate DC 4 !/2 digit DVM to set +/- 5V? on the measurement unit. Might be another procedure but if your setting up frequency you should also set the measurement unit 5V rails.

The PER_CAL procedure itself is pretty easy step by step - just follow on screen prompts. Do a dry run if you like and don't change anything. If you get to a point you confused or not sure, just power off, wait a minute then power on. I've done it heaps of time on a 8924, 8935 & E8285.

73 de Chris ZL1CVD

Per_Cal means periodic calibration and Ref osc is one that should be checked every 6 mo. and maybe every couple of days at first to make
sure everything is OK.?

Yes your GPSDO is fine so long as the signal level and quality meets the expectation of the Per_cal routine, but you should read up the whole
instrument calibration procedure and realize if you don't have accurate enough equipment for one of the steps, you might wind up screwing up
a relatively good calibration.? Make sure you verify you have a DVM that is real accurate.? The 8920 may be more accurate than the rest of your
equipment.? An adjustment there could throw off other adjustments.? A good idea to check things a variety of ways to get an idea what you can
do with what you have.

Focus on calibrations that you can make with the equipment you have and understand the relationship between each adjustment and interactions
with other calibrations.

Thanks to all who replied to my question. I had success setting the DAC's and running Per-Cal on my 8920A. It went from 2445 HZ off at 950MHZ to 6 HZ off. Neat capability!