Automatic Retransmitting Makeshift Repeater

Automatic Retransmitting Makeshift Repeater with MOSFET

This circuit will be of interest to the radio amateur and anyone posessing two radios, (one of which must be able to transmit i.e. a transceiver). It is a self powered (audio derived) repeater circuit for receiving a signal and re-transmitting it via the other radio.

This little circuit can turn two hand-held radios into a makeshift repeater. Any radio will work fine as Radio 1, but Radio 2 must be a Yaesu, or some other type that also goes on the air when its microphone input is shunted with 1-2 kiloohms.

As soon as a radio signal opens Radio 1′s squelch circuit, a tiny amount of energy stolen from the audio signal turns on the MOSFET and it conducts as long as the audio is present. While it conducts, Radio 2 is on the air, retransmitting the content supplied by Radio 1 through C1 and P1.

The BS108 has a conveniently low G-S threshold voltage. The other components’ characteristics are not critical, but it would be wise to stay close to the values shown in the picture, or at least take them as a starting point for testing.

Circuit : Miroslav Adzic

Source: http://www.zen22142.zen.co.uk/Circuits/rf/rxtx.htm

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