Figure 3-7. Simplified FMFB receiver block diagram.
LEARNING EVENT 25: AGC LOOP
The 800-kHz IF is also applied to the AGC detector and amplifier. The AGC amplifier provides an amplified
DC correction voltage to the 60-MHz IF amplifier. The AGC voltage is capable of varying the 60-MHz IF
amplifier's gain over a range of 20 dB.
LEARNING EVENT 26: FMFB LOOP
1. The FMFB loop uses degenerative feedback to effectively compress the FM signal deviation in order to
maintain a narrow IF bandpass. A demodulator using FMFB permits an increase in the output S/N above that of
a conventional FM demodulator at low-signal levels. The increase in the S/N ratio is obtained by processing the
signal input
SS0031
3-22
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