This covers a small number of questions. If you need any additional help please do not hesitate to contact us.
When I plug my military helicopter helmet into my general aviation radio, I can hear but I can't transmit. What is wrong?
Your military helmet has a 5 ohm dynamic microphone and 19 ohm dynamic earphone elements. Your general aviation radio needs a carbon-compatible microphone & 150 ohm to 600 ohm receivers. The best solution would be to purchase a new electret microphone ($65.00) backed by an 18 month guarantee.
Add an amplifier to your dynamic microphone. This is an expensive alternative and only recommended for special purposes.
Purchase a new pair of 300 ohm speakers ($35.00) backed by an 18 month guarantee.
Alternate Solution: Keep your old speakers. This presents two problems. First you will never get max volume from these earphones. Second, because your impedance at the plug is 9.5 ohms, your radio reads this as 15 headsets and draws down the power to the other headsets in your system, so the others with you cannot hear!
If this is an older model helicopter helmet you should remove the Sonex ear cups and replace them with the newer style crushable ear cups. A way to tell the difference is that the crushable have 8 tabs holding them into the ear cup retainer. The Sonex ear cups do not. This simple $45.00 solution provides your helmet with enhanced lateral protection. They are also contoured for a better fit and are found to be lighter & quieter.