VS: [TenTec] Orion TX Audio: Update

Dr. Gerald N. Johnson, electrical engineer geraldj at isunet.net
Fri Oct 31 09:43:30 EST 2003

elstar-mt wrote:
> Audio / Mic;
> I still say:  Most of homemade mic cables has been produced wrong.
> Same on orders, how to do it as in 565 manual.
> Never ground both ends of shield , on rig end.
> Otherwise you cona have a lot of troubles on your audio quality.
> Mark OH3LX.

Depends on whether you are trying to avoid a 50/60Hz ground loop or RF.
In the ham shack where the radio filter ignores that low frequency, and
there IS RF, grounding the shield at the radio end to the case and at
the microphone end to the microphone case is important to keep RF out.
In some microphones it may be possible to not connect the microphone
return wire to ground in the microphone case and so have good RF
shielding AND no ground loop. In my experience, the buzz of a
fluorescent light ballast as acoustical input to the microphone will
make more hum in WIDE band recording situations than any "ground loops"
caused when grounding the shields at both ends.

In the ham station RF into the microphone is a far greater destroyer of
audio quality than ground loops.

73, Jerry, K0CQ

Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.

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