I have been on and off battling this for a few weeks now. It's either too soft, too loud, overdriven, humming, whatever... So I dug into it this weekend and started ripping things apart. I also have a Squelch board that I want to install, The squelch board uses discriminator audio to sence quieting and then give the controller a COR signal. The TKR-820 does not have a COR signal when the internal controller / signaling board is removed, at least none that I can find, I will still look into that.