James Thompson wrote:

Has anyone got a good but cheap circuit to eliminate or surpress feedback.
Im making my son some low power fm mikes to use in his church, but they
get feedback real easy. Is there a simple notch filter per say that I can
add
the the mike section of this. My pcb is only 1.5 by 2" right now.
Thanks.

You can try an equaliser in the amplifier input feed, and try to notch out
the worst feedback frequencies. This will work, but is quite a limited
approach.

The best method is to use a frequency shifter that moves the whole audio
spectrum a few hertz up or down. Surrey Electronics here in England make
such a device, and it's transparent in use - you can't hear it working, but
feedback problems are almost entirely eliminated.
http://reflectionseurope.com/surreyelectronics.html

Chris

--
Everything gets easier with practice, except getting up in the morning!