W7ZOI/K7TAU Spectrum Analyzer - RF Chain Construction

The W7ZOI/K7TAU Spectrum Analyzer, quite simply, is a double conversion, superheterodyne receiver. The two key differences are (1) the first local oscillator is "swept" over a range of frequencies (set by the Timing Base center frequency tune and the span controls) and (2) the output is an electrical signal indicating the relative strength of the signal received. This second difference is quite interesting--it says that at it's core, a Spectrum Analyzer is a radio who's output is the "S" meter (that is, we're really not interested in what the signal "sounds like," but rather, what it "looks like" (e.g. the strength of the signal in the passband).