[AMRadio] 220 vac line

[D. Chester]

I run 110/220 or 120/240 (usually it actually runs about 115/230 but it  may 
vary between those figures at different times of day) from the main service 
entrance in the house to the separate shack. The only point in the whole 
system where the neutral and ground are bonded together is at the main 
service entrance at the house next to the meter.  From  there on out, the 
neutral is treated as a live wire, just like a hot. At the sub-panel in the 
shack I had to add a separate insulated terminal for attaching the 
ungrounded neutral.

I believe NEC recommends that ground be strapped to neutral at a sub-panel 
located in a  separate building, but I  treated it the same as an outlet or 
sub-panel in the same building. Then I  ran a separate #6  bare solid copper 
external ground wire between the ground rod at the service entrance and the 
ground rod I installed near the a.c.entrance to the shack, which is also 
connected to the bare ground wire in the shack wiring. That external ground 
wire between buildings is buried several inches in the soil, much like a 
ground radial.

Some time later, after everything  was wired up and in use, I  measured the 
voltage difference between neutral and ground at the sub-panel in the shack, 
and found it to be a little less than one volt. I experimentally shorted the 
neutral to ground at the sub panel using a clip lead, and there was enough 
current to generate a small spark where the clip touched ground. With the 
short in place, I noticed increased hum in the receiver and some of the 
audio equipment.

I run my audio rack through a balanced 120 volt isolation transformer, with 
a mid-tap at the secondary. The mid-tap is grounded, so I feed all the audio 
equipment with a balanced 120 volt line, each side 60 volts above ground. In 
other words, the a.c. power line to the audio rack is treated just like a 
balanced 500/600 ohm audio line. This reduces ground loop hum and seems to 
help keep RF from the transmitter out of the audio equipment.

Don k4kyv
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This message was typed using the DVORAK keyboard layout.

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