[Elecraft] K3 Microphone Hum

[Eric Ross]

I also had a hum caused when my SIgnalink device was connected to the
computer but NOT powered on.

Eric - WB7SDE

On Thu, Oct 23, 2014, at 11:01 AM, Bill Breeden wrote:
> 
> I noticed an AC hum in the monitor audio in my headphones while calling 
> with one of the W1AW portables.  While wondering if the hum was really 
> in my transmit audio, the W1AW Operator came back to me and reported the 
> hum.  I use a Heil Proset K2/K3 via the front panel microphone connector 
> through a Kenwood style (red band) Heil pigtail.  After completing the 
> QSO I switched to Test mode and I could still hear the hum when I 
> transmitted.  Thinking I had a poor connection, I disconnected and 
> reconnected both ends of the pigtail, but the hum persisted.  While 
> doing that I noticed there was no hum if I activated the push to talk 
> with microphone unplugged from the pigtail.  That had me baffled for a 
> few moments until I remembered that the Proset K2/K3 requires bias 
> voltage from the K3.  At that point I used the "2" button in the "MIC 
> SEL" menu to turn the bias off and on a few times and the hum was 
> disappeared.  I haven't researched the details of the bias switching 
> arrangement in the K3 but it appears that mine needed some exercise to 
> clear a bad connection.  I thought I would pass this on to the rest of 
> the group in case someone else encounters this issue.
> 
> 73,
> 
> Bill - NA5DX
> 
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