[Elecraft] Mics

[Augie Hansen]

Hi Don,

> Can some one tell me what the "magic" is with the heil headsets? I
> already own a bunch of them, plus I prefer the original BM10 over the
> ProSet unless the ambient noise is high. I think I read one post
> indicating that it might just be the Icom element.

Being a long-time Icom user before (and since) building K2 #3302 I have
plenty of experience with rigs that need to be driven with higher level
audio. 

I, too, like the light-weight Heil BM-10 series boomsets, but the standard
Heil dynamic elements (HC-5 or HC-4) have way too low an output level (10dB
below typical dynamic) to reliably drive Icom radios and the K2.

A solution that I have used since the late 1980s is to replace the Heil key
element with an inexpensive (about $2.00) Radio Shack two-lead electret
element. It has a built-in FET preamp that is powered by the 8 VDC provided
on the mic hot lead by Icom rigs. I wired my K2 to do the same, except that
it's a 5-volt level. The electret element preamp can run on 2-10 volts.

If you modify a BM-10 that is wired for Icom you'll need to remove any
series DC blocking capacitor in the connector shell because it will prevent
the electret from operating properly. You'll be rewarded with a mic that can
drive the K2 to full output and you'll be able to successfully trigger the
VOX without shouting.

The easy but expensive way to solve your problem is to spend about $100 to
buy the Heil BM-10-i, which Bob introduced to his product line in recent
years. The Icom versions of his microphones use electrets that are virtually
identical to the ones you can buy at RS or via mail order from a number of
suppliers. [He used to call these mics the solution to the "Icom problem" in
his ads, but they are really the solution to the "Heil problem" of low
output dynamic mics.)

Good luck,
Gus Hansen / KB0YH

Email: KB0YH@arrl.net