I'm trying to calculate measurement accuracy for a spectrum analyzer noise measurement. I have a conditioning circuit with some filtering and switchable dither noise. My test calls for verifying that output noise with the input terminated and dither noise turned off is less than 5 dB above the instrument noise floor. This maybe should have been a noise figure test, but follow on testing uses the SA to verify dither noise band parameters. I can get the SA detector accuracy from the spec and I've used the uncertainty calculator for the U2002A to find an expanded uncertainty of 3.92%. I'm not sure how to determine the S-parameter accuracy using the PNA-X uncertainty calculator to include in the SA total absolute amplitude accuracy.