[RFI] Follow-up static

EDWARDS, EDDIE J EDWARDS, EDDIE J" <eedwards@oppd.com
Mon, 14 Sep 1998 10:19:13 -0500

> >>Found the source of the static.  Utility pole 100 feet away.  The
> neutral wire
>  to a transformer primary was "fuzzing".  (The utility's term, not
> mine.)
> How could a bad neutral connection, (no, not
> ground) a hundred feet away increase the RFI to a neighbor less than
> twenty
> feet away? Any thoughts?  Kelly, KA5MGL
	[K0iL]  The neutral connection "IS" the ground connection both
at the pole xfmr and at the the breaker panel or meter (or wherever they
connect the ground at the entry to the house).  The distribution feed
circuit to most homes is a bi-phase feed: i.e. two different 120V phases
and a grounded neutral.  The voltage across the two phase is then 240VAC
while the voltage across each phase to neutral (or ground) is 120VAC.
The electrical safety ground (the third prong or the green wire) in your
household wiring is connected to the neutral in the breaker panel.  This
is also why you can have a power "outage" in half of your house while
the other side stays hot.

	A bad ground or neutral connection at any of the grounded points
can cause noise as well as other strange effects.  For example, it can
also lead to shortening the life of light bulbs on one phase or the
other.  If the air conditioning is on one phase, when it kicks on it can
drag the voltage down (less than 120VAC) on the phase it's connected to.
If the neutral connection is bad, this can result in an increase
(greater than 120VAC) on the other phase leading to bulbs burning out
prematurely or even other equipment failures if it's bad enough.

	Anything that can cause noise (EMI) can also pick-up noise (EMI)
and conduct it to wherever it can do the most damage, and vice versa.
You will normally induce some RF into nearby power lines since they are
just wires (read "antennas").  This is a not a problem in well grounded
electical circuits, and non-resonant transformers provide some isolation
also.  But a loose connection or loose hardware anywhere in the
electrical system can cause havoc in many ways!  You've found one very
interesting way.  Congratulations!  Now if I can just convince my power
company to quite using those pronged squirel guards that keep getting

	de ed  -K0iL
	Omaha, NE

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