The data sheet that came with my HC4 element a number of years ago
describes the HC3, HC4 and HC5 elements as ceramic having 2000 ohm
nominal impedance. They are designed to work into low (500 - 600 ohms)
impedance inputs and medium (2,000 - 5,000 ohms) impedance inputs. When
used with high-Z inputs, they load down the input circuit and produce
very low output. Heil recommends a transformer to correct this problem.
I use the HC5 in a Heil ProSet to operate my Icom IC-765 but I found it
necessary to build up a small 2N2222 preamp to avoid operating the 765
with the mic gain wide open. Bob Heil assures me that the HC5 will more
than adequately drive the new Kachina that Santa is delivering tomorrow
(!).
>From all this, I gather that the load on the HCx mikes has a lot to do
with their output, and it may be that some of the TenTec rigs are not a
good match while others are. Perhaps in some cases, a transformer might
do the job and avoid using a preamp.
72/73, George
Fairview, TX 30 mi NE Dallas in Collin county
Amateur Radio W5YR, in the 54th year and it just keeps getting better!
R/C since 1964 - AMA 98452 RVing since 1972
W7CW Jay Ostrem wrote:
>
> This may have been dealt with already.
>
> My understanding is that the TenTec factory mic is an electret with a
> preamp built in. (I'm not sure about the mobile mic offering) The Heil
> set up is dynamic with no preamp.
>
> The audio reports from both the HC-5 and HC-4 are excellent, but the major
> gripe appears to be the lack of output to operate the vox.
>
> Heil offers a preamp unit for Icom to deal with the lack of output, as the
> Icom mics operate with a built in preamp.
>
> I've heard mixed reports on adapting the Icom preamp unit for the TenTec.
>
> Should we start bugging Bob Heil, and see if a "TenTec preamp" should be
> offered?
> 73 Jay W7CW
>
> 1AB Ranch
> Gillette, Wyoming
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