I’ve gotten used to using the Icom HS-85 headset with my Icom IC-92AD HT in the car, and would like to be able to use it with the Icom IC-2820H mobile rig I’m contemplating. The speaker-to-earphone connection looks fairly straightforward – the 2820 specs show a 3-conductor 3.5mm phone jack, driven at 8 ohms, and the HS-85 has a 3-conductor 3.5mm phone plug, with an 8ohm earbud, so a simple extension cord ought to work. It looks like Heil makes an adapter cord, AD-1iCM, that has the right connectors for the mike (modular plug on one end, and a 2-conductor 2mm phone jack on the other,) and the HS-85 mike connector is a 2-conductor 2mm phone plug. But the 2820 specs say the mike impedance ought to be 600ohms, and the HS-85 mike is 2Kohms. Should I look for a small transformer with 3.33:1 winding ratio, or something close? Also, I’m not sure what the capacitor is/does on the AD-1iCM (the “C” in the product ID.) Suggestions?