SEM 35 microphone
 

I am having problems getting any volume out of my SEM 35 set while transmitting. It has good range but the volume of the mike is too low. There is a screw in the back of the mike in the handset. Does anybody know if turning it will increase or decrease the sensitivity. The screw was factory sealed so I really don't want to touch it unless I have to. If you have some manpack radio experiance and can help me, let me know.

Cam

Found the fix
 

This was posted on a different board and works quite well.


While chatting with a friend on 6m, I started playing with the
element. One a whim, I unscrewed the mic mouthpiece and tried a
transmission with just the mic elemen held in place with my fingers.
Buckets of audio! Noticable difference even in the "sidetone" on the
earpiece.

Put it back togther, no audio. Hmm, something is up.

If you remember, the German H-33's have a little metal screen to
protect the mic element as well as a rubber cup/gasket with a piece of
clear plastic film glued in place.

From appearances it would be logical to conclude that the screen fit's
inside the rubber cup. And that's how most of the H-33's I've seen
with SEM's have been setup. But that presents a problem, the plastic
film is stretched tight by the bulge in the screen, and not allowed to
move. Since it's rubber sealed, virtually no sound pressure makes it
past the film/screen to the element, and thus low audio.

While it appears to be part of the screw on cap, the gasket/film is
really a removable piece. You can gently pull the rubber cup out of
the screw on cap, and you are good.

After looking at this parts, it's clear the order should be:

Screw on cap
Metal Screen (bulge toward the hole in the cap
Rubber gasket with metal film
Mic Element (carbon button)
Handset

This all assumes the handset is held with the hole for the mic facing
upwards.

When setup this way, the screen does it's job of protecting the film,
while not restricting the audio. (It makes no sense to have the screen
behind the film, it does not protect anything!)

This one simple fix has made the several SEM's used by myself and
friends much more usable. I had been blaming the carbon elements and
planned to replace them with dynamic or electret with a simple amp.
But now the fidelity is quite good!