Doug Smith W9WI wrote in message ...
CL Vancil wrote:
Hello,

I have a project that requires more than 10 headsets that get lots of
rough uses.

I have looked at using multimedia headsets as a cheap source. But
worry about impedance matching and making a remote PTT for them. This
is all for GMRS radios (several brands)using the common mono 1/8
speaker mono 3/32 mic connector.

I have made an experimental box with two stereo 1/8 jacks that just
carry the speakers straight thru and use a simple push button for the
mic's PTT. But get a load "s****zt" just as I press the button.

I've used these with success with HF gear. (TS-940, IC-765, FT-1000MP)

They require DC bias on the mike element. The HF gear has a source of
+8 or +9V DC on the mike jack - I connect that to the tip of the mike
jack through a 10-20K resistor, then tap the audio from the same point
using a 1uF tantalum blocking capacitor. Works great.

Of course the headphone part works fine without modification.

Finding the DC biasing voltage on the GMRS radios might be a problem.


I don't really have access to all the radios to do some hunting and
modifying to each. So it would seem a bias circuit using a battery in
the PTT box is in order. That is if getting rid of this minor
distortion is worth the effort. Something like a .5 uf cap between
the switch and the mic element with a 1K resistor and a single AA
going to ground? Sound about right?

--Chris Vancil