[Elecraft] RF in Microphone

[Jim Kutsch]

First, thanks to all who answered personally and on the list reflector. To
provide more info as several have requested, here's the setup:

The K3S is connected to a KPA500 then to a KAT500 then 25 feet of coax out
to the back porch. There, the coax ends in a  common mode choke, which  in
turn is connected by an 18 inch coax to a DX Engineering 4:1 BALUN. That
feeds a Cobra UltraLite Senior via its 81 feet of 450 Ohm ladder line. The
mic distortion happens with and without the KPA500 but reports say it's
worse at 500 Watts.

The power supply is an Astron RS35 providing 13.8V idle and 13.5V CW key
down at 100 Watts.

The mic gain is set to 45 and compression to 10. Those seemed to give the
correct indication in the ALC meter but the distortion still occurs with 0
compression. I cannot read the ALC indicator myself due to no vision so had
another local ham assist with that part of the K3S setup.

Jim


-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim
Kutsch
Sent: Sunday, March 26, 2017 12:31 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] RF in Microphone

I am a new K3S owner and very pleased. However, on SSB, I am getting reports
that my audio is distorted sounding like RF is getting into the microphone.
I'm using a Heil PR-781 with the XLR3 to 8-pin microphone adapter cable. I
had some RF microphone issues earlier using the PR-781 with a KX3 but a
better shielded mic cable and a common mode choke resolved it. Any
suggestions before I go in search of a different mic? Also, any
recommendations for a boom mount microphone that would be a better choice
for the K3S than this PR-781?

 

Thanks and 73, Jim, KY2D

 

 

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