K3 Hum on mic between 2 rigs

[Elecraft mailing list]

I built a nice boom microphone switch to swap my Heil PR781 between my
K3S and my K3.  The switchbox uses XLR connectors so I can use the Heil
K3 "proper" cables to each rig.  I bought a regular XLR extension cable
for the mic to swithbox.

Well, I used a DPDT switch to switch both pins 1 and 2.  Hum. Then I
used a 3PDT switch for switching all pins, 1, 2, 3.  Hum.

Notice both Heil cables have outer shell at rig tied to mic low. Don't
wanna cut this wire, or should I?

Now all this said, I am powering each rig from a separate power supply.  
My question is, before I go to the expense of purchasing a power supply
large enough to power box rigs at the same time, will this eliminate my
hum or ground loop?

Thanks in advance.

73,
Dan

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[Jim Brown-10]

On Thu,9/24/2015 9:48 AM, Dan Atchison via Elecraft wrote:
> I built a nice boom microphone switch to swap my Heil PR781 between my
> K3S and my K3.  The switchbox uses XLR connectors so I can use the
> Heil K3 "proper" cables to each rig.  I bought a regular XLR extension
> cable for the mic to swithbox.

An important question. Is what you hear HUM (60Hz only) or BUZZ
(harmonics of 60Hz)? It makes a VERY large difference in the cause and
the solution.

73, Jim K9YC


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