Use of Heil HM-10 Dual Element Microphone on Flex-6500

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I have a old Heil HM-10 Dual (HC-4 and HC-5 mic elements) microphone that uses a dynamic element. I would like to use it on my Flex-6500 radio. It has an 8 pin foster plug although I think the wiring on the 8 pin plug was modified at one time to work on my old Icom 735. My question is 1) will the HM-10 work on my Flex-6500 and 2) how do I wire the 8 pin plug to work properly on this radio? Any help or advice would be appreciated.
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Gary Robertson - KY5R

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Posted 5 years ago

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Ken - NM9P, Elmer

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Almost ANY mike will work on the 6500. The question is "will it work WELL!"
This depends upon:
1) is it wired correctly?
2) Do I need the Bias set on or off?
3) How does it need to be equalized?

The neat thing about FLEX and other SDR's is that the EQ can be adjusted to match your mike and voice almost perfectly, if you work at it.

On the HM-10, I would suggest:
a) First rewire the mike plug to match the layout in the Flex manual (or website page)
You will need to match the mike+, Mike-, Shield, and PTT lines. You may not need the PTT lines routed to the front foster connector if you are using the RCA PTT connector in the back with either a footswitch or hand switch. (I use a foot switch)..

b) I would use the wider frequency cartridge on the 6500 and adjust TX bandwidth to match your needs - Wider for Rag chew, more narrow for DX-ing, contesting or weak signals work.

c) I don't think the Heil cartridge needs any bias on the mike line.

d) Listen to your own signal in another receiver - preferably recording yourself and playing it back - so you can hear what you actually sound like and adjust TX EQ intil it is right.

e) If you have another Flex rig, watch the spectrum graph and adjust TX EQ until you get a balanced profile across the spectrum as you talk - the line should be fairly flat, with a slight dip at about 1Khz - not too much on the low end and not too much on the high end. A balanced audio profile is pleasant to listen to and has good articulation.
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Gary Robertson - KY5R

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I have discovered and ordered from DX Engineering a Heil CC-1-XLR-4 adaptor that allows one end of the cable to plug into the HM-10 microphone's 4-pin XLR socket with the other end plugging into the Flex-6500's rear 3-pin XLR socket. Hope it works.
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Ken - NM9P, Elmer

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That is good. I actually prefer the balanced input to the front panel connector. I feel that you can get better isolation/shielding that way. Good luck!
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Mike K5UX

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All of Ken's points are spot-on. The only thing I would add is if you don't want to rewire your old HM-10 cable for the 6500, you can order a HeiSound cable adaptor that mates the HM-10 to a Yeasu 8 pin foster connection from your favorite ham radio store.
All of the Flex radios use the Yaesu pin-outs. If I recall correctly, it's the CC-1Y (Yeasu Heil cables have the yellow band or color code). I rewired mine when my eyes/hands were younger. Now, after many years of ham radio, I have a Heil adaptor cable for all the major brands.
BTW, the Heil HC5 sounds good with the 6500. I have a friend (KB5VE) that has switched between a PR40 and Heil headset w/HC5 with excellent audio reports. EQ it by listening to your voice via the monitor or have a friend that knows your voice listen. One of the really neat things about the 6500/6700 is that you can probably make any mic sound good.

73
Mike