In a message dated 7/29/04 8:08:10 AM Eastern Daylight Time, ah3c@frii.com
writes:
The comments pouring in are fascinating. I was intrigued by the spider ball
design after seing several installed on commercial transmitting towers 1/4
mile from my QTH. The site is a converted cross-country microwave site.
These towers never get direct hits. They are in service 24/7. 2 years ago
my power pole was hit and it wiped out my phone system in the house about
100 ft away. This power pole is located a good 150 ft down the hill from
where my new tower will go. Thus, I believe I can conclude that the
commercial site will not help my cause.
Installed on top of this 8300' ridge, the new tower will be like a beacon
calling out "hit me, hit me" unless I can somehow direct mother nature to
more naturally stream those electrons from the ground through a more
attractive path to the clouds passing by.
Pete,
We had some discussions on this subject while back, between those who noticed
particular antennas/towers configurations and their effect at "repelling" the
lightning strikes and those who learned the stuff from the books and are
"experts and gurus" and say it ain't so.
What my conclusion is, that having large hat (antenna) on the top of the
tower helps to "repel" or shield from lightning strikes. Observing the various
situations, it seems that the effect is due to the "capacitance plate" (large
Yagi) being at the top of the tower (tall structure) and collecting/draining
the
charge from the surrounding area. This prevents buildup of charge and start of
the leader to get lightning bolt do it's thing. Tower and hat has to be all
at the ground potential, with good connections from top to bottom and good
ground system (rods, plates, grids). The higher the tower and larger the
antenna
hat, the more effective "Umbrella" effect. Try not to have and sharp point
structures (mast, 2m antenna) protruding over the hat. Sharp points attract
discharge, get it started easier.
Arguments about yes or no, depend how the tower is terminated. If you have
large Yagi at the top and nothing sharp protruding (i suspect) higher than
radius of the beam, over the beam, the umbrella effect would prevail. If you
have
TH3 and 16' mast above it, with Ringo Ranger, then it would look very inviting
for the lightning to strike (sharp, small area point). So the big difference
is how the top of the tower looks. If it is like a sticking out sword,
lightning loves it. If it is like an umbrella, lightning sees it like a glass
bubble,
with no accumulated charge and no reason for leader to start and lightning to
strike. Not 100%, extremes could happen, but there are enough of us to vouch
that it is (99.9%) HAPPENING (avoidance of strikes). Lightning then strikes
around the "bubble".
The classic lightning protection is with lightning rods, porcupines/spider
balls (very small capacitance hat) and heavy gauge wires connected to the
grounding system to attract and dissipate the lightning. The ham radio way
protection helps to shield the area and equipment from the strikes by repelling
them.
It costs nothing, just knowing how to setup your antenna systems. Surround your
house with tall towers and put the biggest beams all the way on the top,
minimizing any sharp protrusions above and whole system at the good DC ground
potential.
I know W8JI does not agree with this, but this would be subject #7 that he is
wrong about :-)
Reality IS!
Yuri, www.K3BU.us
www.computeradio.us home of DRone and Tesla Cup Contest Sept. 25-26
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