spectrum analyzer

a laboratory measuring instrument used for studying the frequency spectra observed on the screen of an electron-ray tube as well as the pulse- and amplitude-modulated oscillations in 3– and 10–cm wave bands. In order to obtain oscillographic patterns of the spectra of the oscillations under investigation in “power-frequency” coordinates, a superheterodyne radio receiver is used in the spectrum analyzer. In this receiver the incoming oscillations are weakened (if necessary) by attenuators, transformed according to frequency, and strengthened; then they enter on the vertically deflected plate of the electron-ray tube. The frequency of the receiver’s oscillator varies linearly by ±8 mHz (in a 10–cm band) or ±30 mHz (in a 3–cm band) in step with the saw-toothed tension sweep, which is simultaneously fed into the loops that change the heterodyne’s frequency and on the horizontal plates of the electron-ray tube. Frequency calibration is provided for in the analyzer by an oscillator with calibrated markers, having smooth control of amplitude and frequency ranging from 1 to 10 mHz. The spectrum analyzer can measure the oscillator’s frequency drift, minor differences in the frequency of two oscillators, and so forth.