Topband: Elimination of Treadmill RFI on 160 meters

[Jim Brown]

On Tue,1/27/2015 4:08 PM, Tom W8JI wrote:
> The flaw in this system is that differential voltages between current 
> carrying wires are not measured, and anything on the safety ground 
> isn't measured.  Noise voltage is only measured from individual 
> current carrying conductors to ground, and the safety ground is 
> grounded and not measured.

Exactly right, Tom. A common design/manufacturing defect is that the 
green wire fails to make contact with the shielding enclosure, but 
instead goes to common on a circuit board, which may or may not ever 
find the chassis. This defect, which is the power system equivalent of a 
Pin One Problem, puts noise on the green wire. You may remember that we 
corresponded several years ago about Astron power supplies, in which a 
very common defect is that the green wire is soldered to the mounting 
lug of a terminal strip, which is insulated from the chassis by paint. 
The same mounting lug is the point where V- is bonded, so it never finds 
the chassis either. AND, wiring for both V- and the green wire act as 
antennas for both TX and RX.

I have long suspected that similar defects are at least partially 
responsible for noise conducted onto coax and AC lines from consumer 
products of all sorts.

73, Jim K9YC