Thanks! I tried but I don’t see the effect with noise gen, maybe my measurement is not quite right. Simply punching in a couple of frequencies (60Hz and 200Hz) that I’ve already seen differ in amplitude with the Measure function also has different peak amplitudes in FFT output. Since the frequencies are so low I’ve verified stability of siggen amplitude output with an AC voltmeter and it’s stable within 50uV or so, nowhere near the diff in magnitude measured by the scope. Hmm…