I'm trying to wire up an external mic with PTT and a speaker to my Yaesu FT-250R to basically use as a VHF base station when I'm not mobile. Unfortunately, I can't find anywhere a description of how to wire that up. The FT-250R has a single 3.5 mm TRRS plug for connecting an external mic/speaker. Just hooking up a plug with bare wire leads and fiddling around with things, I'm pretty sure I've figured out which are AUDIO OUT, GND, and PTT. However, a lot of the diagrams for similar radios that I've seen have MIC and PTT going to the same ring on the 3.5 mm connector. They then show you having to insert a capacitor in the MIC line and a resistor (typically ~2k) in the PTT line to decouple the two. In my fiddling around, inserting a 2k resistor between GND and any of the other leads did not cause the radio to key; but shorting one of the leads (the one I assume is PTT) to GND did cause it to key.
Anyway, I kind of have it figured out, but I want to be a little more confident in what I'm doing before I go much further so I don't ruin my radio. If anyone has any advice or access the the appropriate wiring diagram, I'd really appreciate it.
Yes this probably would be easier to buy the CT-44 adapter that Yaesu makes, but I'm a homebrew kind of guy and have enough spare parts to do this a few times over.