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Pilot USA high noise cancelling mic question


New Member
Apr 23, 2018
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I have a Tigermoth and have just fitted a Trig VHF com, 12v .
Impedance of the set is 300 ohms.
My Campbell Classics flying helmet always had issues transmitting, always garbled to the reciever. I could always hear just fine , transmit was always readability 2 !. Helmet has a 2 position switch to internally match mil to ga impedance as required, tried both, settings ,no luck.
To resolve the issue I parted company with the Icom a200, installed a new aerial set up, VSWR 1.5, and have now decided to replace the mic in the headset.
I purchased a Pilot USA branded Electret Mic that need a voltage supply to operate. How can I hook this into my existing system ? The old carbon dynamic mic is non powered. I unable to locate any info on this any where, was hoping some instructions may come with the mic, but doubt it. The mic is the PA-9EHM
version specifically for high noise environments like the Tiger.
Happy to make a battery box if that’s what’s needed.
Any help here would be greatly appreciated.
Aussie Tiger driver.


Well-Known Member
Jan 9, 2013
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Did you purchase an amplified electret mic kit? For example, David Clark's M-7/DC Amplified Electret Mic kit is a direct replacement for the carbon mic's that come on their H10-30 and H10-40 headsets.

If you have a naked electret mic there are ciruit drawings out on the ham radio web sites that will get you going.

Best of luck,



Well-Known Member
Oct 5, 2007
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Hi there, I know your situation well, the Tiger, the helmet and the mic.

A few things will cause a bit of grief here. The Campbell helmet uses an extra amplifier within the earcup of the helmet as the mics they use are unamplified dynamic mics (not the best quality ones either), they way they wire them will likely mean the electric won't work. I have done several change overs to the PA-9EHN and usually I just remove the amplifier from within the earcup.
These mics work well with the Trig but you may find you need to wind the squelch right up on the radio as they don't like rogue emf, which the Tiger produces a huge amount of. Do you have a shielded harness on your Tiger? Are you using BTH mags or have you the Slick Mag conversion.


Registered Users
Supporting Member
May 30, 2009
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Springfield, WV
Alas, those old biplanes were just NOT made for radios.:rolleyes:

That said, Good luck!


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