A Transistorized Multiplex Demodulator for FM Stereophonic Reception

This paper describes two FM multiplex demodulators which have been designed for systems employing transistorized FM tuners and stereo AF amplifiers. One adapter uses a frequency doubler as a carrier regenerator and employs the sum-and-difference method of restoring the two stereo channels. The other adapter uses a locked oscillator as a carrier regenerator, a time-share detector, and a stereo program indicator. Automatic switching is accomplished between stereo and monaural reception. Performance of both adapters is discussed, as well as design problems encountered