Microair Mic Problem

Working with a friend on his radio problem and his mic seems to be
overdriving. He's sure it's an electret mic, and it's an older Microair
radio. I seem to recall having to use an r-c network across the mic of
another radio last year in Houston on a club glider, but I didn't make
notes and don't remember the values of the resistor or capacitor. The
other possibility is to turn down the mic gain at the pot on the side
of the radio... Suggestions... Experience....

Thanks in advance.

Jack Womack