HP 54710A User's Reference Manual page 341

FFT Menu
FFT Basics
Amplitude Measurements
For best amplitude accuracy on peaks
1 In the channel menu, make sure the source impedance and probe
attenuation are set correctly for your application.
2 In the acquisition menu, set the Sampling mode to real time and set
Interpolate to off.
3 In the channel menu, set the Scaling for almost full scale deflection.
4 In the FFT menu, use the flattop window.
5 Press the shift key, then the More meas key on the keypad. Then, make an
FFT magnitude measurement.
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