[Elecraft] re: Proper connections for Heil Pro-Set?

[Mike McCoy]

Date: Thu, 16 Jan 2003 16:42:06 -0800
To: elecraft@mailman.qth.net
From: Richard Fall <rfall@witsend.com>
Subject: [Elecraft] Proper connections for Heil Pro-Set?

> I recently bought a Heil Pro-Set with the HC-5 microphone
> element to use with the K2 for SSB operation.

> What does the Heil microphone "appear to be" in terms of
> the proper P1 wiring--i.e., which section of table 2 in the
> K2SB manual should I use?  The Elecraft MH2, because it's
> really a Heil microphone? Or, because the MH2 was specially
> made for the K2, with a high-output condenser element, is a
> different connection appropriate?

> Also, the Elecraft website has a design for an external
> microphone amplifier for the *HC-4* Heil element--does this
> also apply to the HC-5 element?  That is, *must* I have this amp
> to use the Pro-Set?

> I currently have the K2 microphone configuration block wired
> for an ICOM HM-12 microphone, and I'm hopeful that the Heil will
> work without rewiring, but the evidence I've seen indicates
> otherwise.

> Any thoughts?

> - Rich
>   WA6FXP

Since I had an extra HM-36 laying around I too initially wired my K2 header
for an Icom mic. I then picked up a Heil BM-10 headset at a swapmeet and
found myself in a delimma... I wanted to keep use of the HM-36 AND have the
use of the Heil BM-10 but having to change mic header plugs every time I
wanted to change mics would be a major PITA.

So I built my own Heil adapter for the BM-10 with parts from Radioshack
(inline 1/8" & 1/4" jacks, 8 pin mic plug & 1/8" headphone plug and using
some shielded audio cable I had laying around). That way I could wire BM-10
signals to the 8 pin mic connector like an Icom to 'satisfy' the K2 Mic
header plug. Note the Heil BM-10 doesn't like/want 5v on the audio line so I
had to place a teeny 100uf cap in series with the signal on pin 1 to block
the 5v coming from the K2 that normally powers the HM-36 preamp.

I also added a PTT switch to the 'Homebrew Heil adapter', something the real
Heil adapter doesn't provide. I found a small momentary pushbutton switch at
Radioshack that fit almost perfectly in the (extra) black plastic strain
relief housing of their inline 1/4" jack. Assembled you have a pushbutton
PTT switch with a nice 'grip'.

The BM-10 doesn't provide the gain the HM-36 does (then again, it isn't
preamped either) but it works great when you're needing 'hands off'
operation.

73,
Mike K5PU

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