Back when I was in school I used to work a lot with the spectrum analyzer, to the point that I was able to dig up low power signals from bad noise conditions and plot very fancy results. A few years of not using the spectrum analyzer made me forget quite a few things. However, reading this document that Anritsu is offering for free brought back all my memory. It is also a very interesting resource to read just for the fun of it.

Guide to Spectrum Analysis