I have a friend that has a boat , and he would like to mount a loudspeaker in his cokpit.
The loudspeaker would play FM-Radio , but when there is activity on his VHF radio he would like it to automaticly come out of the same loudspeaker.
The VHF has a 3watt external speaker connection , and it is there i have to conecct some kind senso circuit to detect activity , above squelch level.
I was thinking of something along the input circuit of this velleman kit.
And then connect it to an AVR that activates a relay , with a timer that keeps the relay (VHF) active for some adjustable delay 30sec ... 2 min. But it seems like this one requires 2 watt to activate , and was hoping for some suggestion to an appropriate input sensor circuit , to the VHF radio.
Maybe a cap in front of the resistor (i just need to trig on ac activity) , and a lower resistor value , and maybe a zener along with the 1n4148 or ????
Any hints are welcome.