On 1/27/2011 5:15 AM, Michael Coslo wrote:
> I've always thought that way too many things are called "ground".
YES, YES, YES, YES! The use of the word "ground" to describe circuit
common, or the chassis, causes MUCH confusion and leads to extensive
muddy thinking. That muddy thinking extends to WRONG questions in the
exam pool, to WRONG admonitions by manufacturers in manuals for their
equipment, and WRONG thinking about solutions to RFI. And all of these
errors are pervasive throughout ham publications, including those from
ARRL.
> I think that the main message that I take from Kurt's post is that when we
> see what he has seen, you can bet that there will be other problems. They
> need fixed.
>
> I recommend homeowners who can safely look at their wiring do so.
More good advice, including that from Paul, W9AC in another post in this
thread. When I bought a 100 year old home in Chicago I rewired about 90%
of it. In the week before I sold it, 20 years later, a wiring fault in
the other 10% of it that I didn't get to a bad splice in the ceiling of
a kitchen) caused a loss of power in that kitchen. It didn't cause a
fire, but I had to get an electrician in to chase it down in time for
the papers to be signed to close the sale.
I've found numerous problems in the 25 year old home that I bought here
in California, everything from mis-wired outlets to the improperly
grounded clothes dryer that Dale described yesterday, to improper
connections between ground in the main house to ground in the 4-room
building that houses my shack, and really stupid errors in grounding of
the power system. At the main service entrance to the house, the
neutral was properly bonded to the chassis of the backbox, but there was
no earth connection! Rather the wire that SHOULD have been an earth
connection ran about 40 feet to a water spigot for a garden hose, which
was fed through the hose via PVC pipe. Ground was then carried to the
second building, where there was another bond between neutral and ground
(another no-no), and a ground wire that led from a sub-panel in the
kitchen, up the wall, along the eaves, and back down to a ground rod.
That was the only earth electrode I could find anywhere, and it was MUCH
longer than it should have been.
I strongly agree with Paul's recommendations for shack wiring, but I'll
take it a step further. In general, ALL equipment in the shack should be
plugged directly into outlets that share the same green wire back to the
panel, or to outlets mounted in steel backboxes that are bonded
together. And I recommend installing enough outlets (using multi-gang
back boxes) so that all equipment can be plugged directly into those
outlets rather than into outlet strips. The primary reason for all of
this is minimizing hum and buzz when interconnecting computers and other
audio gear to our rigs.
A single 20A circuit provides enough power to safely run at least two
100W radios, a couple of computers, and a 500W power amp, and it could
handle two of those amps in an SO2R or multi-single contest
configuration (that is, with only one rig transmitting at a time).
It's also good practice to increase the wire size by at least one
gauge, especially if the run to the shack is fairly long. That's because
the impulsive waveshape of the current drawn by power supplies for
electronic equipment causes IR drop to be much greater than if the load
current were a pure sine wave.
73, Jim Brown K9YC
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