Spectrum Analyzer Accuracy

[damn_dirty_ape]

Hello,

I have two spectrum analyzers that are giving me very different results.

Using the first analyzer, I used the 'channel power' measurement function on a local FM station.  The result is about 39.5 dBuV.

I then unplug the first analyzer and plug in the second one at the antenna feed.  Using all the same settings, the new result is 30.97 dBuV.

I'm not trying to do certification testing or anything, so accuracy isn't crucial, but a 10 dBuV difference is a lot.

The two analyers are the Anritsu MS2720T and the Keysight N9343C.  They advertise .5 dB and 1.3 dB accuracy, respectively.

Are the channel power measurements (39.5 dBuV and 30.97 dBuV) inside the range of variability that you would expect, or am I doing something wrong?

Thanks,
Pete

edit:  i accidentally a word

[w2aew]

Are you certain that you have the same Channel Power settings (channel BW, RBW, detector type, etc.) for each analyzer?  Make sure that there aren't any amplitude corrections on one of the analyzers.

[Kalvin]

Compute the error in dB and see how much that is compared to the advertised accuracies. You may also want to check how far you are from the noise floors of the instruments.

[German_EE]

Depending on where your antenna is I would expect to see a change of 9uV as you moved around the room. The only way I would consider testing two spectrum analyzers side by side is a signal generator, three calibrated lengths of coax and a resistive 50 ohm splitter. Just for good measure I would swap the connections over after the measurement and see if I could repeat the results.

Finally, if two spectrum analyzers give different results then the obvious next step is a third spectrum analyzer. See the 'Test Equipment Anonymous' post in the General Chat section.