Consider a continuous wave signal being displayed on a spectrum analyzer at f=5GHz. It's a single peak. When I put marker on the peak it shows me the peak measured power. Now when I decrease the span of the instrument from 10MHz to, lets say, 1MHz, the measured peak power is increased. Can someone explain why this is so?
I am sure it has something to do with the RBW of the instrument. Also if the power changes with span, if I just need to measure the peak power should I be using zero span mode?