Rec.radio.amateur.homebrew? There are several amateur projects out there
for spectrum analyzers, but none of them go to 30GHz directly. However,
often people use a low frequency spectrum analyzer and a transverter to move
the entire spectrum down, which works fine for many purposes. The amateur
radio guys have a band at 27GHz, so transverters from, e.g., Down East
Microwave could probably be tweaked to instead operate around 30GHz.
Actually building your own equipment at 30GHz is doable but rather involved;
the wavelength is 10mm -- or under 5mm on a typical circuit board, so
anything that you're going to consider 'lumped' is very, very tiny (0201
resistors are great fun... and do you have a wire bonder at home?) and
mecahanical dimension tolerances become critical. Last month at Microwave
Update in Seattle, Paul Drexler presented a 47GHz waveguide filter where his
mechanical tolerances had to be within half a mill (.0005") to insure good
You might want to provide a few more details as to what you need -- how much
bandwidth you need would be a good start.