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Re: Lightning hits



Hi, Jon.  No, you should never connect any grounds to the utility
neutral (the white wire in most systems).  The usual green wire
is a safety ground wire, coming from the utility ground rod at your
service entrance.  This green ground wire is connected to the chassis
or cabinet inside your equipment.  It's purpose is to protect you in
case
of a fault, such as the 'hot' lead of your power cord becoming shorted
to the chassis.  If this happens, your chassis or cabinet rises to 120V
with respect to earth.  If you touch the cabinet with one hand and a
grounded object such as a water line or the coax from your antenna with
the other hand, about the best thing that can happen is that you get
knocked flat on your backside.  With the safety (green) wire connected
properly to that chassis, a circuit breaker pops instead.  This safety
green wire is to protect you from a bad shock if there is a fault.  I
literally cringe when I see three-prong 120V plugs where someone has
snipped off the round safety ground pin.

Yes, there is ultimately a connection between the neutral (white) wire
and the equipment ground (green) wire- but this connection is made in
one and only one spot, at the service entrance.  It should never be
made inside equipment.  Inside your equipment, you will find that
neutral (white) wire is carefully insulated from the chassis.  In days
gone by, when we had only 2-prong wall sockets,  AC/DC radios and TVs
often had the neutral wire connected to the chassis.  This was so
dangerous
that people got killed regularly.  The 2-prong plug was 'polarized',
meaning
one plug blade was wider than the other, to keep you from plugging in
the plug
backwards.  If you plugged it in backwards, the hot wire was hooked to
the
chassis, and the chassis assumed a potential of 120V with respect to
earth.
This plugging in backwards problem was pandemic.  Electricians or
homeowners
would hook up the two wires on the socket wrong, and the stage was set
for
a disaster.  This problem was lessened by going to the three-wire
system,
where the safety ground wire is connected directly to the metal chassis
or cabinet, reducing greatly the chances of making the equipment hot
with
respect to ground.   There are still plenty of 3-wire sockets wired
wrong
out there (with the line and neutral conductors reversed) but the green
safety ground wire prevents most of the resulting fault-induced shocks
by popping the associated circuit breaker.  A ham friend of mine
recently
checked his wall sockets and found 40% of them were wired wrong!

Please excuse this rather long-winded reply, but I think this is an
important
subject, not well understood by many.

Best regards,  John  W5EME

Jon Ogden wrote:
> 
> on 12/11/00 9:39 PM, John Harrington at johnh@ih2000.net wrote:
> 
> > By the way, I don't recommend hooking your station ground to the utility
> > neutral wire, for safety reasons.  If the utility neutral connection breaks or
> > corrodes you may be providing the return wire for your stove and refrigerator
> > through your radio equipment grounding system.  The utility neutral should be
> > grounded at only one spot- at the service entrance
> 
> This is the whole reason though why you are to have your radio grounds
> connected to the electrical ground.  I agree with you that to depend on the
> electrical ground for RF is silly.  The tower should definitely be grounded
> as you say.  However, if the tower is grounded, having a 600 Ohm line
> hanging going to the safety ground won't matter.  You effectively are adding
> a 600 Ohm resistor to ground in parallel with the ground connection of your
> tower.  The important thing is making sure the tower is WELL grounded and in
> good, conductive soil.  If it isn't you are screwed.
> 
> Your statement about not connecting radio equipment to the utility neutral
> is troublesome.  Our radio equipment is by necessity connected through this
> neutral just by virtue of the fact that we have power supplies that plug
> into the AC mains service.  Perhaps I did not read it clearly, so let me ask
> a clarification: When you say attaching ground to the utility neutral, do
> you mean the green ground line or the white line?  If you mean the white
> wire, I whole-heartedly agree.  However, I think that there is still some
> connection internal to our own equipment where there is ultimately a path of
> some sort between the neutral and earth ground.
> 
> 73,
> 
> Jon
> NA9D
> 
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
> 
> Member:  ARRL, AMSAT, DXCC, NRA
> 
> http://www.qsl.net/ke9na
> 
> My President is George W. Bush -> The legal winner in Florida
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