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EXA Signal Analyzer N9010A

Question asked by Janka on Oct 26, 2010
Latest reply on Oct 30, 2010 by xmo
We have a problem with measuring amplitude spectrum. Using sinus signal amplitude 20mv and frequency 100kHz, we measure the max value of the amplitude around 3mV (we tried it for many other value). In document 89601-90011 on page 509, we found
Attenuation=RefLevel+PreAmpGain+ExternalGain-RefLevOffSet-MaxMixerLevel+IFGain (we do not know any members of this equation e.g. difference between  PreAmpGain and ExternalGain (it is the same member on the menu) or how count with RefLevel and MaxMixerLevel in Volts or in dB and how transfer V to dB (20log or 10log)),
and we expected that it could solve our problem by setting ExternalGain. Experimentally we found out, that to get expected values, we have to change the ExternalGain according to frequency range. But we still do not find an universal algorithm, how to change this ExternalGain. Sometimes it is -10.5dB sometimes -2.25dB. Please could you let me know what to do?
Thank you very very much for answering