[Elecraft] Re: Aviation headset

[jhaynes@alumni.uark.edu]

I sent a hint and kink on this topic to QST but I don't think they have
ever published it.

The modern aviation headset is designed to be compatible with the old
radios that used carbon mikes.  The earphones are obvious; and they are
higher impedance than the 8 ohm stereo earphones but will probably work
with no problem.  To run the microphone you need to supply DC, and the
easiest way is to use the DC that is available on the mike jack of
most radios and use a transformer.  DC into the transformer, the other
end of the winding to the ring of the 3 conductor mike plug, and the
sleeve of the plug to ground.  Then the other winding of the transformer
goes to the mike input and mike ground on the radio.

Now here we get into an area that I know little about.  My Kenwood TS-940
uses a low-level mike, and all the amplification inside the radio, so I
use the Radio Shack 1000:8 ohm stepdown transformer.  I have the K-2 wired
like a Kenwood, for what that's worth.  The guy I did this for also has a
Kenwood radio, so that's how we did it.  I have another friend who has an
older ICOM radio and there the microphone has a built-in amplifier.  So
I guess it needs a higher-level mike signal than the Kenwood and the
Radio Shack 600:600 ohm transformer might be more appropriate.  Somewhere
I wrote down the number of the appropriate Switchcraft jack for the 
aviation headset.  Anyway, you can make a tin box with the jack and the
transformer inside and a mike plug for your K2 coming out the other side,
all parts available at Radio Shack.

Jim W6JVE