On Mon, 28 Nov 2005 15:16:16 -0800, Dan Hearn wrote:
>Have you considered the possibility of RF coming in via the house wiring and
>the line cord? I have solved 2 problems with a few turns of the line cord
>thru a ferrite torroid.It is a very easy thing to try. 73, Dan, N5AR
Coming in on the line cord, or the antenna current finding its counterpoise
through the power system's safety ground? It could be either. When you stick
a choke on the power line, you are breaking (or increasing the Z) of that
COMMON MODE path, but you are not affecting the differential mode RF (that is,
between line and neutral).
Another mechanism is illustrated by this war story. Over the weekend, I strung
a temporary wire antenna 10 ft off the ground at a new qth and heard a lot of
broadband noise on 160, 80, and 40. I reduced it a lot by winding five turns
of the AC cord for the 14VDC power supply around a #31 toroid. (I would have
done more turns, but the only line cord I had was too thick to do so). Here,
the noise was on the AC ground, and was being added in series with the antenna
circuit.
Jim K9YC
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