Aviation Headset Microphone Interface

I had completed version number two some time ago with the help of a nice aluminum chassis, a Hammond 1590B case that is popular with the Guitar Pedal and the Box Mod enthusiasts. In my case it’s not an amp or a current booster but a passive audio exchange for Aviation Headphones that uses a microphone for amateur radio communications.

In this application I use a Push To Talk built in and also a switch for some passive filtering as well as some knobs for some adjustment of mic tone.

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The phono jack goes to the audio output in the radio and the 8 pin mic plug is where a normal handheld mic would go. The other connections are jacks for aviation microphone and aviation headphone earphones.  Power for this is supplied by the radio and powers the electret microphone in a boom on the headset.

 

IMG_20151121_171926The circuitry inside is all point to point wiring as this was much easier to deal with than any circuit board. Went together fast and is pretty solid construction.

All controls are at hand with tone, mic tone and PTT control easily at hand.

This unit is fun to use, and is practical and works with all the brands of aviation headsets. Telex, David Clarke, and Lightspeed with ANC. I tested them all. but I prefer the Lightspeed with this system the best. Features that can be added later are two more buttons for up and down frequency control.

Aviation Headset Microphone Interface Version 1

Headset Mic Schmatic 3This is the interface I designed that allows me to plug my aviation headset with mic, into my transceiver.  It is relatively simple but took some planning to get the microphone portion to work. The unit chassis is a metal box that I obtained from some other system, perhaps from some other torn apart radio. It is nothing more than a 2.5 x 2.5 inch cube. Any project box could work as long as there is room for phono type jacks.

 

Headset Mic Schmatic 2The microphone circuit was built on a simple perf board and installed into the interface box.

 

 

 

 

Headset Mic Schmatic 4The mic circuit is powered from the # 5 pin out on my TS-570 Mic socket. The mic input is DC blocked by two capacitors and a resistor. The resistors can be variable to allow for adjustments. The 8 volts is adjusted by a 2k variable resistor for gain.

 

Sockets were obtained from an old push to talk system and built into this box. The socket for headphones is also installed into the box but it is direct through to a male 1/4 that also plugs into the radio phono jack.

Attached is the switch part of my old Push to Talk switch and it is wired to the radio jack as a normal grounded switch that is typical for these types of radios. Consult your radio manual for the PTT pinouts.

I used a cable from a old hand held mic that attaches to the mic circuit and this supplies 8v and mic PTT ground to the box.

 

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