I had an Icom SM-20 for several years that I used with my Icom 775 radio.
I really didn't care much for the SM-20 as the up and down buttons stopped
working also, the mic stand was to short and I had to hunch over to talk on
it. As far as I am concerned, the SM-20 is not worth what it cost. I had a
chance to trade the SM-20 even for an Icom SM-10 and I jumped at the chance.
Before trading, I had the SM-20 repaired and cleaned up good. I now use an
Icom SM-8 with my Icom 775 radio. I believe your best bet might be the Heil
ICM mic that the guys were talking about. At least the audio is good and the
price is much better. Good luck
Best Wishes,
FRED ADAMS W4HC
FIGHT TRUTH DECAY