K3 Microphone Hum

[Bill Breeden]

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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[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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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