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From: "Kenneth Goodwin" <>
Date: Tue, 4 Jan 2011 14:30:18 -0600
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This is what bothers me about power companies saying they will cover any
damage if their surge protection device fails to protect the equipment in
the house.  How can they insure anything not under their control?  I would
bet dollars to donuts they don't insure anything unless their monthly
charges are to pay for a blanket insurance policy too.  I've had more damage
coming thru the cable TV and telephone lines then I've ever seen coming in
on the power line (26 years in the same house with 4 indirect lightning
hits, never a direct hit which makes sense statistically).  I know for sure
that one of the near hits came thru the TV/Internet/VOIP cable line since it
took out every device hooked into to the house network (computers, TVs and
VOIP telephone).  The wired telephone line was protected by a telephone line
surge device but I relied on the cable provider to take care of their line.
As I found out to late, all they did was tie the shield to ground at the
power line ground rod.  The best one was when a near hit welded all of the
house security reed relays shut due to the radiated energy (EMP) picked up
by the very long loop of the series connected reed relays in all of the
house windows.

As K4FMX said, "A whole house protector is a good idea but be sure to also
bond all other
cables such as phone lines, cable TV, and your antenna cables etc to the
same ground point or very near where the whole house protector device is
installed. If you don't do that the whole house protector could make things
worse than not installing it at all because the whole house protector is
going to force the ground leads to your TV, radios etc. up to the same
potential as the hot lead carrying the lightning strike! If your antenna, TV
or phone cables are not referenced to the same place as your whole house
protector then there will be a difference of potential at your equipment."

Unless you have the opportunity to build your house or shack from scratch,
the option of having the ground point of the power lines and the RF lines
collocated is doubtful.  As W1CMC indicated (below) the best he could do was
tie the grounds together with #6 or #4 THHN wire.  I tried one better by
connecting the power and RF ground rods (separated by 50 feet) together with
heavy copper wire (# 6 ??) buried in the ground with a ground rod every ten
feet.  I am pretty sure that in a lightning hit, this won't suffice as a
single point ground but it was the best I could do.

As W1CMC said, "I recently bought a house that has the main electrical panel
at the
front (grounded to a water pipe) and had (past tense) both OTA and
satellite TV coax coming from the antenna/dish through the back of the
house.  The 75 ohm coax runs were grounded with a rod driven into the
back of the house, and there was a long long #6 or #4 THHN wire
running from that grounding block at the back of the house to the
panel at the front. What's wrong with this picture?  Well, that long run of
#6 or #4 has
an inductance.  That inductance becomes an impedance at high
frequencies during a lightning strike, which means that the voltage
potential at the panel ground and the coaxial ground could differ as
K4FMX said, "Sometimes by many thousands of volts!" That voltage difference
between the coaxial ground and the panel
ground will appear across the electronics that are connected to both
grounds: i.e. the satellite receiver and television that are both
plugged into the wall and connected to the antennas.  Voom! Once again, as
K4FMX said, "This means that ALL equipment and lines
connected to that ground system must rise together to avoid damage."

I contend that lightning will do whatever it wants to do although I'll admit
the cell phone towers seem to have done a good engineering job but they
started from scratch and had plenty of money too.  Last time I checked the
XYL wasn't going to allow me to build a cell phone tower equipment enclosure
as our residence.

Ken K5RG


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