Methods of Measuring Adjacent-Band Radiation from Radio Transmitters

A review of three possible methods of measuring or estimating adjacent-band radiation characteristics of a radio transmitter is given. These three methods differ in the type of signal applied to the transmitter and may be termed the two-tone, normal signal, and thermal noise methods. Measurements on a multichannel single-sideband transmitter using each of these methods are presented to show that there is a good correlation between the normal signal and thermal noise methods. An empirical method for calculating the slope of the adjacent-band radiation as a function of frequency from the measured two-tone distortion values is given, and the measured and calculated slopes are shown to be in fairly good agreement.