NTE789 Stereo Multiplex Decoder
Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a lowdistortion
preamplifier and simultaneously applied to both signal, generated by a local voltagecontrolled oscillator
(VCO), is counted down by two frequency dividers to a 38kHz signal and to two 19kHz pilottone supplied
by the FM detector is compared to the locally generated 19kHz signal in a synchronous detector.
The resultant signal controls the voltage controlled oscillator (VC)) so that it produces an output signal to
phaselock the stereo decoder with the pilot tone. A second sychronous detector compares the locally generated
19kHz signal with