Advantest R4131D Spectrum Analyser, 10 kHz - 3.5 GHz

The Advantest R4131D spectrum analyser is a wide band, very sensitive receiver. It works on the priciniple of "super-heterodyne receiver" to convert higher frequencies (normally ranging up to several 10s of GHz) to measurable quantities. The received frequency spectrum is slowly swept through a range of pre-selected frequencies, converting the selected frequency to a measurable DC level (usually logarithmic scale), and displaying the same on the CRT of the Advantest R4131D. The CRT displays received signal strength (y-axis) against frequency (x-axis).