Ok, gotta finish the mic amp and speech amp stages today. My 50 year old D104 mic, that I found on eBay for $35, came today. It is filthy, old, and the cable is crap but it does work if you bypass the cable.

I happened to have the Aeroflex here for the weekend, which is helpful, as it has an OUTSTANDING general purpose scope in it, in addition to the suite of RF test functions. Second photo is the D104 wired temporarily to the CH1 scope input. The mic cartridge is almost unmanageably sensitive on the '3920, it sounds good over the test channel, but it's a bit echo-y even at low setting. I think my transmitter will be way less sensitive so probably not going to be a problem, the 3920 is an outstanding instrument.