NO "water pipe" should ever be used as a service ground... I thought
the code was changed to actually bar that practice entirely.
______________________
Clay Autery, KY5G
(318) 518-1389
On 04/05/20 23:06, David Christ wrote:
That I understand but if the ground from the entrance breaker panel to a water
pipe from the street is 30 feet long, can it radiate interference to AM radios
near it (both AC and battery powered)? If so could it cause RFI at even higher
frequencies?
David K0LUM
On Apr 5, 2020, at 10:35 PM, Jim Brown <[email protected]> wrote:
On 4/5/2020 5:16 PM, Frank O'Donnell wrote:
I'm not the OP, but can you remind us what buzz (multiple harmonics of 60 Hz)
might signify?
60 Hz hum is nearly always magnetic coupling in some form; buzz is generated in
the three phase power systems used to distribute power. While few of us have
3-phase power in our homes, the systems out on the street ARE 3-phase. These
harmonics are present because a very large fraction of the loads on the power
system are some form of rectifier-capacitor-input power supply; most of the AC
load current flows at the positive and negative peaks of the 60 Hz sine wave to
recharge the filter cap. This causes the current waveform to be a series of
positive and negative pulses, and the IR drop causes the top of the voltage
waveform to be rounded off. And we know that any distorted signal is composed
of harmonics.
In an ideally balanced three-phase system with only sine-wave loads, the
neutral current goes to zero. But when harmonics are present (the distortion),
harmonics whose number is divisible by 3 ADD in the neutral rather than cancel.
They also add in the ground!
Buzz is generated by leakage current in the power system; it can couple into
our equipment by a couple of mechanisms. It can be eliminated by 1) proper
bonding within our home and station; and 2) getting power for all station
equipment, including computers and other accessories, from the same AC outlet,
or from outlets whose green wires are bonded together. All of this is addressed
in the slide deck for tutorial talks I've done at Pacificon, Visalia, and to
several ham clubs.
http://k9yc.com/GroundingAndAudio.pdf
73, Jim K9YC
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