From: "Jim Morgan" <>
> Klas - Does the added moisture make the membrane more sticky? If so,
> couldn't you surround the mic with a DC heating element the keep the
> membrane and electrode dry? Would the steady state magnetic field created=
by
> the heating coil affect the mic?
The electric charge on the capsule is always drawing the membrane toward
the backplate. I'm not sure the membrane get's more sticky to end up
sticking. In any case that's mostly with pretty large diaphragms.
The heater I think of for this would be from Astronomy. With the
telescopes radiating to space, they easily end up colder than the air
around them, thus collecting dew easily.
The solution is dew heaters. These are heating straps in various lengths
that are wrapped around in the appropriate places. It's a fabric strap
with velcro. The heater is controlled by a small solid state controller,
and powered by 12 volts, usually from a car battery. I use them, but use
a small motorcycle battery. The brand that has more or less owned this
market is Kendrick, available via places that sell astronomy stuff. It
would be about $100 list for the controller plus one heater, the
controller can run up to 4 heaters. You can find lower prices, and they
do turn up on ebay.
As far as the magnetic field, it's a little worse. It's DC, but the
controller is cycling the heater to control it's temp. I doubt it would
be a problem, but only test would find out. I've got the heaters, but
don't have the mic to try.
Note the power used is just a few watts per heater, you don't have to
warm things very much. The homemade is just a string of resistors
soldered together.
Note it would take some time for this heater to warm a already cold and
damp mic, you have to use them from the beginning so the damp never gets
going. If I turn it on for my 8" SCT, with dew on the front optics it
would take nearly a hour to clear the dew.
Walt
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