END_OF_TRANSMISSION_BEEPER

Published:2009/7/13 5:21:00 Author:May | From:SeekIC

Release of push-to-talk (PTT) switch at end of radio conversation activates time delay for antenna changeover relay, keeping transmitter on air long enough to transmit 800-Hz tone burst indicating transmission termination. Tone is generated in simple one-transistor phase-shift oscillator powered by voltage present between PTT terminal and ground in receive mode of transceiver, which may be any voltage between 6 and 30 VDC. Transistor can be any small-signal NPN silicon with gain of at least 300 at 1 mA, such as 2N930. Parts marked with asterisk must be matched within 5%.-E. Hombostel, Automatic Beeper for Station Control, Ham Radio, Sept. 1976, p 38-39.



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