On 7/3/2013 7:37 PM, Joshua Hintze wrote:
Thank you for all the suggestions thus far.
I'm using an ICOM IC-A110 VHF radio. I was able to find some schematics/block diagrams in the service manual here:
http://elektrotanya.com/icom_ic-a110,_a110e_service_manual.pdf/download.html
This is my first time trying to dig through a radio and find a COR. I'm not sure either where to get a discriminator audio signal either.
Detecting squelch break in AM is a lot different that breaking squelch in FM... iirc, you have to depend on the AGC circuit to do what it's supposed to do in order to detect a signal level delta greater than the background hash, which is a variable. FM looks for the detector to open up when the frequency swing happens...a bit more binary than AM transmissions, which means there's a constant noise level vice AM (just listen on the HF bands to see the difference in the noise levels from minute to minute...). Kind of hard to detect amplitude changes as being a legitimate carrier vice noise, since they're both the same general modulation envelope, whereas in FM, the intelligence is carried in a different mode than the background noise. Don't know whether I'm explaining it clearly enough, but it's in that general neighborhood or some such. Just what are you trying to do? BB