The radio audio input is probably a higher level because of the electret cartridge inside the mic. And some mics might also have a small preamplifier stages inside. I would guess the electret cartridge first and maybe followed with a preamplifier stage... Mototorola does it on some of their microphones.
You should also watch for some radio mic inputs to have both the preamplifier and dc audio voltage on the same line. There are straight forward was to add and extract dc voltage off a mic and line audio leads with simple resistors (and sometimes chokes) with capacitors. You can find a really nice mic preamplifier circuit for the controller output tx side on the Midland group radio page. If you're not a member you can ask one of us to get a copy of the mic preamp for you. It's a very simple but great working two-stage transistor job that's pretty easy to make and easily powered of a single ended supply. Impedance mis-match is probably not the bigest reason for the low audio level problem... cheers, s. > "georgiaskywarn" <[EMAIL PROTECTED]> wrote: > > Started a project at the end of LAST summer and never got finished. > Using a ADI247 as a 220mhz link radio. Blew something up in it (in > looking for cos), sent it off, got fixed, now just getting back to the > project. *I Thought* I had decent tx audio out of it into the RC210 > controller hooked to it. However now I barely get a whisper out of my > tx audio. I can hook a mic to it...no problem with the audio, works > fine. Almost sounds like an impedance mismatch. > > Ideas? > Thanks, > Robert > KD4YDC >
