On Wed, 03 Mar 2010 13:45:23 -0500, johndtate@post.com wrote:
>Much of the hum was magnetic pickup and
>moving things and better grounding solved that.
Clarification. I can believe magnetic coupling as the cause of 60 Hz
hum, but a connection to EARTH has NOTHING to do with magnetic
coupling. Magnetic coupling requires a loop for current that couples
to a signal path, and that couples with a magnetic field.
If by "better grounding" you mean that you cleaned up wiring to
eliminate that current loop, I can believe that. But that isn't
"grounding." BTW -- magnetic coupling can also be reduced by putting
the field and the coupled circuit at 90 degrees to each other. For
example, by rotating the box containing the power supply, or by
rotating the loop. Or my making the loop area smaller.
73,
Jim K9YC
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