Prdufresne
Member
I'm building a mobile cross-band repeater using a 2M mobile station and a 70cm HT.
Getting the audio to repeat from 2M to 70cm was simple enough as I fed the audio output of the 2M radio to the external MIC input of the HT and turned on VOX.
Getting the audio to repeat in the other direction has proven more tricky. I built a simple VOX circuit that triggers a relay DPDT relay to simulate the PTT press and connects between the HT headset output and the MIC input of 2M radio. The issue I run into is that since the audio is switched by the relay, when the transmission ends, and the VOX releases the relay, the EMI generated by the relay switching triggers the VOX again which causes a feedback loop with the relay clicking on and off continuously.
So one side of the relay is switching the input audio, and the other is triggering the transmitter (by attaching a pin to ground).
I tried filtering the relay "click" with a capacitor, but it has been hit and miss.
My alternatives, are:
- Find a solid-state alternative to the relay that will pass the audio un-altered and provide ground
- Get rid of the VOX altogether and trigger the relay on carrier detection. (requires modification of HT)
Suggestions?
I know someone will suggest getting a dual-band mobile unit with cross-band repeat function, but I've come so far, I'd like to make this work.
ThanX
Getting the audio to repeat from 2M to 70cm was simple enough as I fed the audio output of the 2M radio to the external MIC input of the HT and turned on VOX.
Getting the audio to repeat in the other direction has proven more tricky. I built a simple VOX circuit that triggers a relay DPDT relay to simulate the PTT press and connects between the HT headset output and the MIC input of 2M radio. The issue I run into is that since the audio is switched by the relay, when the transmission ends, and the VOX releases the relay, the EMI generated by the relay switching triggers the VOX again which causes a feedback loop with the relay clicking on and off continuously.
So one side of the relay is switching the input audio, and the other is triggering the transmitter (by attaching a pin to ground).
I tried filtering the relay "click" with a capacitor, but it has been hit and miss.
My alternatives, are:
- Find a solid-state alternative to the relay that will pass the audio un-altered and provide ground
- Get rid of the VOX altogether and trigger the relay on carrier detection. (requires modification of HT)
Suggestions?
I know someone will suggest getting a dual-band mobile unit with cross-band repeat function, but I've come so far, I'd like to make this work.
ThanX