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Frequency-Modulation Radio-Telephone Receivers

These are superheterodynes built to operate at the very high frequencies employed. The intermediate-frequency amplifier operates at about 10 megacycles in many sets. The set shown in Fig. 29 includes a limiter and a discriminator, but, of course, a ratio detector may be used instead.

Figure 29. Block diagram of the superheterodyne radio-receiving set for frequency-modulated signals.

In frequency-modulation broadcast transmitters pre-emphasis circuits2,51 are used which emphasize the high frequencies, and de-emphasis circuits2 are used in the receiver to return the frequencies to their proper relative strengths. Such circuits, which are used to further overcome noise, have been omitted from the drawings shown here. Frequency-modulation receivers52 using what is called a fre-modyne circuit for detection are also used. This circuit employs the principle of superregeneration discussed in many books on radio.5 The folded-dipole antenna5,6,53 is often used with frequency-modulation receivers.


Home Radio Systems Frequency-Modulation Radio- Telephone Receivers

Last Update: 2011-05-30