[Milsurplus] Carbon Mic Subs

[Jim Haynes]

On Sat, 23 Mar 2013, David Stinson wrote:

> Put me down for Hi-Z Dynamic.
> Most commonly available non-computer,
> non-electret mics.  I do NOT like electrets, which pick up every
> flea-fart in the county.

Someone pointed out in QST a while back that there are different kinds
of electret mikes.  Most of them, the ones you get at Radio Shack, are
pretty flat over a pretty wide frequency range.  But there are some
with the frequency response tailored for voice communication.  At the
time of the QST article the writer noted that the one he had been
recommending was no longer available, but that there was probably
something to take its place.

I don't know anything about the electret elements in the carbon telephone
transmitter replacements I bought, but I would assume they have a
frequency response appropriate for telephones.  Maybe not - maybe they
depend on the bandwidth of the rest of the telephone plant to restrict
the bandwidth of the whole system.

I got the elements from Mike Sandman www.sandman.com who deals in
telephone stuff.  They are made to fit into a G-type telephone handset
and were quite inexpensive, less than $5 as I recall.  I suppose you could
cut one up to make it fit into something else.

There's an article on the web about putting an electret into an H-33
handset, but it's pretty serious surgery.  Replacing a T1 element is
duck soup with the part from Mike Sandman.

Aside from militar stuff:
There has recently been a lot of discussion of microphones on an Icom 
IC-7200 list.  It seems the earlier HM-36 mikes made in Japan are good
right out of the box, but the later ones made in China are horrid.
There are several versions out there of simple modifications to the
circuit to improve the Chinese model.  I have a Chinese one and made
the modification without ever trying it first; after modification I
tested with a friend across town and he said it sounds fine.

Jim W6JVE