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Author Topic: who knows about aircraft mic/headsets?  (Read 839 times)
WB4SPT
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Posts: 141




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« on: April 08, 2013, 04:49:12 PM »

I've got a couple.  One is a Telex, the other is a low end Procom something.  Anyway, I did a somewhat successful "converter box" to make these work with my T4X.   It took the usual low voltage DC source thru a resistor, series cap, and a step up transformer to get enough voltage to drive the Drake.  My issue is EMI.  One headset is affected by high power fields on 75m, the other on 40m.  High power being 1kw into a dipole 60' away.  Now, I know that old time airplane mics used to be carbon type, and these are a far cry from what modern headsets use, and sure enough, there is a IC inside these headsets with a bunch of supportive passives.  I'll take it that the IC mimics the carbon mic action, basically feeding a more modern electret mic from the boom.  I tried some ferrite beads with no good effect.  Anyone out there solve aviation headset EMI issues? 
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VA7CPC
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Posts: 2383




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« Reply #1 on: April 08, 2013, 10:53:42 PM »

Try google:

ham radio "dave clark" headset

will get you quite a few hits.

Have you tried the obvious -- putting a few turns of the mic lead through a ferrite bead, to form a little toroid inductor?  That often works.

.          Charles
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K0IZ
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Posts: 737




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« Reply #2 on: April 09, 2013, 08:42:40 AM »

Your step-up transformer is likely the EMI problem.  Aviation headsets are "carbon mike equivalent", meaning the external specs are basically same as the old aviation standard carbon mike.  I suggest you take a look at my Hints and Kinks article in April 2010 QST.  It has an adapter (no tranformer).  It works well for me, and for the many who have copied the circuit.  Even being used by at least two "super" contest stations.
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