Stuart Longland wrote:
C2 is an EMI supression thing... I have gotten away without it on
radio, but I found I got *lots* of complaints when I tried to use a
headset lacking C2 on my Nokia 3310 mobile phone. (I did have C2, but
I had it down near the plug in the phone.) If you take apart a GSM
mobile hands-free kit, you'll see a small chip capacitor soldered on
the back of the electret capsule.

Ah. I've not tried that circuit on VHF, let alone UHF, let alone a phone, but I'm quite familiar with the mess a mobile phone can make of a
microphone signal!

(I work for a TV station. Our newsreaders used to think if they turned off the ringer, they could leave their phones in their pockets while on the
air. Two or three interrupted stories later, they learned to leave their phones in their office....)

On amateur radio, it can't hurt, and can only make your signal better
IMO... I think Heil and other companies do a similar thing for
electret microphones.

What value are you using? (I would suppose something on the order of 500pF would be adequate. I've seen people use rather large values in an attempt
to reduce HF audio response..)

--

Doug Smith W9WI
Pleasant View, TN EM66