Well, I need the radio to be able to use the microphone. I know that it is not the easy solution but it is the one that I am going for. I do not want to open up the radio so I am going to try and design a circuit so that the mic and the URI can be connected into the microphone jack. I will also include some digital logic so that if both the URI and the mic a trying to key up, then only the signal from the mic will go through. I will try and upload a schematic later.
You didn't say what kind of radio it is (or if you did, I didn't see it). The best and/or easiest way to implement this is going to vary with the type of radio. At the very worst, you need is a SPDT switch (CD4053 appropriately biased, reed relay, whatever) and a couple of steering diodes. But depending on the radio, it could be as simple as hard-OR'ing the PTT's together and resistively summing the audio. You likely have way more audio output available from the URI than you'll need to drive the mic input, so there's a good chance all you need to do is add enough series R in the audio coming from the URI to prevent loading the hand mic. Assuming you're using the AC-coupled output from the URI you don't even have to worry about DC-blocking the mic bias. --- Jeff WN3A --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus