HP8920A problem

[Stan]

Hi people
I have a HP8920A service monitor.
When I turn it on, I passed the test itself.
I have a problem measuring the transmitter power.
Namely, the measurement of power is about 20% less.
Also, while the transmitter is activated, the power level slowly decreases. For about 60 sec., it drops by 1W.
When measuring the power level on the spectrum analyzer, there is also slightly less reading (approximately 10%), but the level is stable.
Does anyone have any suggestions, where is it, and how to solve this problem?
I know the problem is not simple and it's probably necessary to calibrate.
However, calibration firms are mostly in the United States, so sending devices from Europe is very complicated and costly.
Thanks in advance!
Stan

[mojoe]

There are some built-in tests that you can run. The on screen instructions will walk you through them. You might also download the manuals from the Keysight/Agilent/HP web site.

How much power input is your unit rated for? There are several input attenuator options. It is marked on the front, at the RF input connector (assuming someone didn't swap it out and not mark the front panel correctly). How much transmitter power are you using?

The input attenuator is rated for continuous power input. It is derated to so many seconds per minute when you exceed that rating. For example, the standard 60 W attenuator can be used for 100 W for brief periods, with a longer cool down time. I don't remember the exact numbers, but it is in the manual.

As for the spectrum analyzer showing slightly different levels vs the power meter on the TX screen, that is normal. While you are downloading manuals, get the spec sheet as well, and look that over.

[mojoe]

One other thing. for a simple and inexpensive RF power reference, go to http://w1ghz.org/small_proj/small_proj.htm, scroll down the page, and look for "RF Power Reference". I have one and it provides a very accurate -10 dBm reference at 50 MHz.