electret mic hookup

[mrat]

I put together this mini FM transmitter. It seems to work because I
can hear the buzz in my radio change whenever I mess with the coil or
the on/off switch. But I can never hear the audio that should be
coming through.

I don't know that much about this type of thing, but I took the mic (I
got it at Radio Shack) and tried to hook it up directly to a speaker
using several different schematics I found for electret mics.

www.epanorama.net/documents/audio/electret.html

All I got was nothing except for when I attached the battery I can
hear the speaker flutter a bit.

Does this mean I have a bad mic or am I just not hooking it up
properly?

 

[Walter Harley]

"mrat" <frustratedmaster@yahoo.com> wrote in message
news:6d9556ef.0404051522.22db94db@posting.google.com...

I put together this mini FM transmitter. It seems to work because I
can hear the buzz in my radio change whenever I mess with the coil or
the on/off switch. But I can never hear the audio that should be
coming through.

I don't know that much about this type of thing, but I took the mic (I
got it at Radio Shack) and tried to hook it up directly to a speaker
using several different schematics I found for electret mics.

www.epanorama.net/documents/audio/electret.html

All I got was nothing except for when I attached the battery I can
hear the speaker flutter a bit.

Does this mean I have a bad mic or am I just not hooking it up
properly?

Microphones, even when they are working properly, only generate a very weak
signal. They require amplification in order to be heard on a speaker.

Have you tried powering the FM transmitter with a known-good source of
signal, such as the output of a CD player? That could help you determine
whether the problem is with your microphone circuit or with your mini
transmitter.

By the way, if you study carefully you'll see that the two schematics on the
web page you cite are identical except for the value of the capacitor. That
suggests that the author of the page is simply posting circuits he's found
elsewhere, without any effort to understand or test them. That will tend to
lead to frustration on the part of people who build those circuits, such as
you.