I had great success looking at microwave signals with a contraprion made from a
surplus tektronix mixer(1-8ghz), a broadband input using a 3db attenuator before the mixer a low noise amplifier with resistive termination after the mixer? setting the gain of the whole signal path to 1. Using a PLL that has 4 programmable output frequencies (Made in Ukraine) I can look at signals all the way up to 8+Ghz with the most used frequencies at the flip of a switch. It tracks the signal as seen on my commercial analyzer to within about a db +-.I lose about 10db overall dynamic range by putting the amp after the mixer but it was a lot easier than to find a wideband high IP3 preamp that was flat from 1-8gig.
John
John Cunliffe W7ZQ