Two-way FM radio system operating on a single channel and provid

Details Two-way FM radio system operating on a single channel and provid Two-way FM radio system operating on a single channel and provid

1976-03-31

1977-07-19

Griffin, Robert L.

Telegraphy

Systems

Printing

178 58R, 325 57, 343178, H04B 144, H04B 154

Patent

active

040371581

ABSTRACT:
A two-way FM radio transmitter-receiver operates on a single channel and automatically samples the channel during transmissions to sense the presence of a carrier wave. The transmitter is actuated by use of a transmit key which starts timing means to produce a time interval, and at the end of the time interval a sample generator is actuated for a very short time period to turn off the transmitter, disconnect the antenna from the transmitter, and connect the antenna to the receiver. A detector coupled to the squelch circuit of the receiver at the transmitting station detects the presence of a carrier wave on the channel, and the detector output produced in response to a carrier wave acts to hold the transmitter off and allow the receiver to reproduce the received wave. When the transmitter is turned off for the short time period, the absence of the carrier will cause the FM receiver at the receiving station to produce a burst of noise. This results in an output from the squelch detector which is utilized to blank the audio output by initiating action of the timing means to produce the first and second time intervals followed by a blanking period. The time interval produced by the timing means, and the blanking period, can be somewhat longer than the time interval and the sampling period used during transmissions. By changing the duration thereof, the same monostables are used to provide the blanking action during reception as are used to provide the sampling action during transmission.

REFERENCES:
patent: 2435010 (1948-01-01), Knapp et al.
patent: 2501986 (1950-03-01), Brockman

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