Hello !
I have an IC-725 and I use the Heil HC-4.
To adapt the mic to the radio I use a very small and
basic mic amplifier (a mic pre-amp kit I bought in electronics
store). The amp uses one single transistor and a get the power
from mic plug that has a pin with +8V DC.
It is working OK, just as well as my desktop mic, the SM-20 !
Before this I used to connect it just using a capacitor in series
with the mic to cut the DC offset, but the audio didn't have
enough punch to drive full power of the rig.
Good Luck !
| Pedro Pedroso | CT1ELP |
| Eng. Electrotecnica e Computadores | Founder member of GPDX |
| (Telecomunicacoes e electronica) | ct1elp@amsat.org |
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| Address: P.O.Box 116 , 2801-902 Almada , PORTUGAL |
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---------- Forwarded message ----------
From: kl7ra <kl7ra@blizzard.gcgo.nasa.gov>
To: Robert Thain <g0hgw@yahoo.com>, CQ-Contest@contesting.com
Subject: Re: [CQ-Contest] Heil mics and the Icom-735
Hi Robert
The resistor that needs changing in the 781 is impossible to
get to and I have had the radio mostly apart for other reasons.
Changing the resistor may help but adding mic gain by their
Icom amp (which is the same thing) didn't do much for the VOX
and it was still "fussy".
The best fix that works great is to get their ICOM Heil headset
which uses the Icom DC voltage to power its electret element.
It's new and now available.
73 Rich KL7RA
>
>Following a recent message regarding Heil microphones
>and Icom radios:
>
>I'm trying to locate the feedback resistor in the mike
>amplifier that Heil recommends increasing.
>Its the feedback resistor you have to increase by
>150K.
>
>1) Has anyone done this mod and what did you think of
>the results? Was it worth while ?
>
>2) I have been told that it is resistor R235.
>Can anyone confirm this and help me locate it ?
>
>Thanks
>Robert
>G0HGW@yahoo.com
>
>
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>CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
>Administrative requests: cq-contest-REQUEST@contesting.com
>
>
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