Tony,
Every single "military microphone" I've ever encountered [a lot]
required very close talking to get any output. They're often used in
extreme noise environments and that's one simple way of removing the
ambient noise such as on an aircraft. They are often used right up next
to your mouth, and would be "breathy" except they had limited high freq
response. Designed for a very specific purpose. Don't know how any
would sound in ham service with a pre-amp, but Jim, K9YC, is on this
list, he retired from a career as an audio professional and so far, he's
my go-to-guy. Maybe he'll read this and offer his take.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
Tony wrote on 3/20/2022 4:25 PM:
All:
I finally got the chance to test the Knowles HC-3 military microphone
element I ordered. The eBay seller claimed that it had the same
frequency response as the vintage Heil HC-5 and it is very close in
that respect. However, it's not nearly as sensitive as the Heil HC-5
so it requires A LOT more mic gain.
It also needs to be close-talked to the point where you're lips touch
the element screen. Move 1/2 inch away from the mic and the audio
drops off to nothing. The Heil HC-5/4 I have were also made to be
close-talked, but they have enough sensitivity so you can be 2 or 3
inches from the element and still maintain good output.
I asked Bob Heil about all this and he said Knowles built the HC-3 for
him which eventually morphed into the original HC-4 and HC-5. He also
mentioned that a pre-amp could be used with the HC-3 to make it work.
So the $40 dollar military surplus HC-3 has the same high articulation
as the HC-5, but it lacks sensitive. I should also mention that the
HC-3 is larger by a 1/4 inch give or take so it's not a drop in
replacement for Heil headsets like the BM-10.
Tony -K2MO
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