Unfortunately Frank Gilliland has exaggerated his numbers
due to insufficient experience and too much time listening to
myths. His numbers will be exposed as fiction.

Field experience says repeatedly that antenna and radio can
suffer direct strikes without damage. That is proven about 25
times every year atop Empire State Building since the 1930s.
According to Frank, they must suffer damage 25 times per
year. Let's start with his numbers.

Millions of volts? Yes. But same voltage does not appear
everywhere in a circuit - basic circuit theory. Those
millions of voltage are in the sky. Surge protection is about
making those millions of voltage appear elsewhere which is why
industry professionals discuss impedance. A low impedance
connection to earth means no millions of volts.

Millions of amps? Only in dreams. Most lightning is below
20,000 amps and of such short duration as to not be high
energy. Lightning typically so low energy at the strike
location (not to be confused with what is miles above) that
well over 90% of all trees struck leave no indication of that
strike.

How big need a wire be to shunt (earth) lightning? Even the
US Army training manual TM5-690 requires 10 AWG wire to
conduct the direct lightning strike without damage. Same wire
found in 20 or 30 amp AC electric boxes because lightning is
not the millions of amps so often claimed in urban myths.
Unlike Frank, numbers are provided by multiple, reliable
sources.

Another who does this for a living:
From Colin Baliss "Transmission & Distribution Electrical
Engineering":
Although lightning strikes have impressive voltage and current values
(typically hundreds to thousands of kV and 10-100 kA) the energy
content of the discharge is relatively low ...

or Martin A Uman in All About Lightning
Most of the energy available to the lightning is converted along
the lightning channel to thunder, heat, light, and radio waves,
leaving only a fraction available at the channel base for
immediate use or storage.

In short, Frank Gilliland's numbers are classic myths.


Pre WWII ham radio operators demonstrated what was required
for protection. First they would disconnect antenna and still
suffer damage. Then placed antenna lead in a mason jar, and
still suffered damage. But when antenna was connected to
earth ground, then no damage. Neither a mason jar nor "one
of those big blade switches" sufficiently blocks destructive
transients. Of course not. Lightning was not blocked by
miles of air. Is a mason jar or knife switch to do what miles
of air could not? Of course not. For no damage, provide the
destructive transient what it wants - earth ground.

zeeeeeeee's antenna installation is demonstrated by a
figure in TN CR 002 The Need for Coordinated Protection
(corrected URL)

http://www.erico.com/public/library/...es/tncr002.pdf

Need anyone suffer damage from direct lightning? Of course
not. Such damage is considered a human failure because proper
earthing is so effective and so inexpensive. Another
professional who makes that point in direct contradiction to
posted myths:
http://www.harvardrepeater.org/news/lightning.html
Well I assert, from personal and broadcast experience spanning
30 years, that you can design a system that will handle *direct
lightning strikes* on a routine basis. It takes some planning
and careful layout, but it's not hard, nor is it overly
expensive. At WXIA-TV, my other job, we take direct lightning
strikes nearly every time there's a thunderstorm. Our downtime
from such strikes is almost non-existant. The last time we went
down from a strike, it was due to a strike on the power company's
lines knocking *them* out, ...
Since my disasterous strike, I've been campaigning vigorously to
educate amateurs that you *can* avoid damage from direct strikes.
The belief that there's no protection from direct strike damage
is *myth*. ...
The keys to effective lightning protection are surprisingly
simple, and surprisingly less than obvious. Of course you *must*
have a single point ground system that eliminates all ground
loops. And you must present a low *impedance* path for the
energy to go. That's most generally a low *inductance* path
rather than just a low ohm DC path.

Important point. This professional did not say
'resistance'. He said 'impedance' which is why wire length is
so critical. 'Impedance' is why an incoming wire (antenna,
CATV, telephone) must first drop down to make a short
connection to earth before rising up to enter a building.
Just one of the "careful layout" techniques learned from
underlying theory tempered by decades of experience.

zeeeeeeee's tower requires earthing to meet human safety
requirements of National Electrical Code AND to provide
transistor safety. Earthing required twice over. Once
properly earthed, then even unplugging for protection would be
unnecessary - as has been demonstrated too many times at too
many locations since before WWII.


Frank Gilliland wrote:
In , w_tom wrote:
The earthing is required by NEC for human safety AND also
provides transistor safety. If lightning is provided a path
to earth ground via that exterior rod, then it too will not
seek earth ground, destructively, via your radio. Direct
strike lightning damage is that easily avoided.

Wrong. If the coax is plugged into the radio when lightning hits
the antenna, it's safe to assume that your radio will fry. Period.
Doesn't matter how much protection you have. Why? Because lightning
packs a few million volts (not an exaggeration) and will jump just
about any gap to ground. But gaps are also resistors, and since
lighting also carries a few million amps (again, not an
exaggeration), you are going to have a SIGNIFICANT voltage
potential on your coax. In fact, the potential and current are so
high that the core insulation breaks down for the full length of
the coax and it is literally cooked from end to end. I've seen it
more than once. And that's WITH proper grounding!

Unplug the coax from the radio when not in use. If you want to use
a "device", get one of those big blade switches so there is a big
gap, and wire it so the antenna is shorted to ground when not
connected to the radio.