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BOOM (Swan neck) MICROPHONES

A short note about microphone types:

Most new avionics (Xcom, Icom etc) are designed to work with "Carbon type" or "Carbon Equivalent" microphones.

"Electret" microphones designed for "AVIONICS" are very small, electronic "condenser" microphones that also work on the same bias voltages as do Carbon type microphones. "Most" telephone, cellular telephone microphones are of "electret" types, but will not work with the bias voltages provided by "AVIONICS" and are not suitable for this use thus it is necessary to add a pre-amp to the Electret and then it is equivalent to the old style carbon microphones which we once used in aviation.

Dynamic microphones can be of an "Amplified Dynamic" (equivalent to Carbon Microphone)  or "Un-Amplified". Most European avionics (Becker, Dittel etc) are designed to operate NON-Amplified Dynamic microphones and have microphone circuits for these types, however, most newer European (eg Becker 6201) avionics typically also have additional circuits to allow for use of "Electret" or Amplified Dynamic microphones as well, either by jumpers within the radios or specific pin-outs in the wiring.

Electret microphones offer excellent noise cancellation and are smaller, more inexpensive and typically lighter than Dynamic types; however it is generally agreed that the Dynamic microphones produce a more natural sound and higher microphone volume output than do typical Electret types, and do not require the user to be as close to the microphone, or in many cases have the microphone touching the lips of the user as may be necessary with the Electret element type microphone.

Thus "Amplified Electret" in my opinion are best used in motorgliders where when mic is near your mouth it works well, but when the microphone is 25cm away from lips there is almost no volume in the transmitted signal. This is adjusted through microphone gain in the radio and often these days is in the software.

Ian Mcphee
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