[CQ-Contest] ClearMic use with QC15 or QC25

[Bob Henderson]

I am one of those who purchased a ClearMic for QC15 from Headset Buddy only
to find problems due to feedback between headphone output and mic input
made it unusable for SO2R.

I contacted Headset Buddy to explain their ClearMic was incompatible with
my radio set up.  I use a pair of K3s.  They offered me a full refund
inclusive of shipping costs and told me to keep the mic.

The ClearMic languished in a corner of the shack for a while before I
decided to investigate the problem.  It quickly became apparent this was
due to use of a high resistance ground lead shared between mic and
headphones.  The lead is 1.2m in length but the screen (shared ground) has
a DC resistance of roughly 1 ohm which is enough to see a proportion of
headphone audio shared with mic output.

I solved the problem by cutting the supplied lead around 7cm from the plug
which attaches to the QC15 phones.  I re-used the lead I had just chopped
off for the headphones and paralleled a separate single core screened cable
for the mic.

With the mic and QC15 grounds now separated the feedback problem is solved
and the ClearMic QC15 works very well.

I guess a few other folks might have ClearMics sat around waiting to have
their grounds separated.

73 Bob, 5B4AGN