OK, I know I've mentioned this before, but I think I'm on to something now... I wanted to have a stand alone repeater linker, kind of a crossband repeater, that would link uhf and vhf repeaters together without needing to make any changes to either repeater. The problem I ran into is when the first repeater finishes transmitting, the linker will hear the second repeater (if the pl doesn't drop out) and will key up the first repeater again. This cycle will continue until you turn off the linker. I tried this with my crossband radio and it causes the same problem.
One solution is to have the repeater controller stop transmitting their pl right after the COR drops. Not all repeaters do this, so you would have to be selective as to which repeaters you link. The solution I came up with today is to use a microcontroller with a built in a/d converter. If after the first repeater stops transmitting, the microcontroller can sample the audio coming from the second repeater. If I go through a high pass filter, I should (might) be able to determine if the audio is 'dead air', a courtesy tone, or someone talking. If it's dead air or a tone, I won't key the linker. I can then wait for the COR from the second repeater to drop, or listen for audio. Do you think it will work? - Jerry
