For 15 years I've used a 35' mast of R-S steel sections supported in one
plane by the elements of an inverted Vee and in a perpendicular plane by
guys at about the 2/3 height of the mast. I can put this up and down
easily by myself, by adjusting the guys to approximately the correct
length (leaving them as is when making no change) and walking the bottom
away from one end of the dipole. The bottom stands on a short piece of
treated 2 X 6 with a landscape spike through a hole in the 2 X 6 to
"nail" it to the ground and to keep the mast in place. The feedline is
supported on one of the guys down to the ground and away in a direction
perpendicular to the dipole, and there is an I.C.E. lightning suppresser
where it enters the house. It ought to have a distributed ground system
at the mast and an inductor across the dipole for better lightning
protection and to more effectively dissipate precipitation static.
When I designed this house, I inquired about lightning protection. The
best source of information was the books by Uman and the University of
Lots of lightning rods are the result of busy salesmen. The State of
Minnesota fire marshal does not keep useful statistics on either
lightning induced fires or the effectiveness of lightning rods.
Commercial buildings typically include perimeter lightning protection
in this state. The U of MO recommends lightning rods on buildings that
are exposed, that is, on high ground and not sheltered by taller
buildings, trees, or other objects.
According to Uman, 90% of lightning strikes may be grounded through #12
copper wire. The other 10% are the high energy events that typically
include sustained current exceeding 100 amp between strokes. This
explains the survival of many items, including a Hy-gain vertical that I
watched take a direct hit but on which I could find no damage (the coax
was disconnected and totally outside the house at the time). I've also
observed a direct strike on the commercial tower on which our club's
repeater antennas are mounted. The repeater was in use at the time, and
its antennas were protected by PolyPhasor suppressers. The strike
appeared to hit the tower horizontally near the mid-point of the tower,
not far from where the repeater antennas are. The transmission of the
repeater was interrupted only momentarily and not damage was detected.
Another of our club's repeaters suffered serious damage and lots of wood
in the building housing it was charred by lightning energy that entered
on an ungrounded phone line. The ground wire to its suppresser was not
connected. Phone connections were welded and charred wood traced its
path to our repeater cabinet.
I haven't read the current edition of PolyPhasor's book, The Gounds. An
earlier version was informative, especially when studied in conjunction
with Uman's books. However, I've not read any single source that gives
the amateur complete guidance for assessing the variables associated
with a particular station and designing a lightning protection system
for that station. I recommend that each amateur study a lot but be very
critical to try to separate the facts from the myths. In the end, each
must decide what risks to accept.
73 de WO?W
David Greer wrote:
>I've had good experience putting a mast up against a
>two-story home with a bracket at the roof peak. At the
>bottom, I put the bottom of the mast in a bucket
>filled with mix-it-yourself concrete. It was plenty
>sturdy for a VHF beam turned with a TV rotor.
>73, Dave, N4KZ
>--- "Tim, N9PUZ" <email@example.com> wrote:
>>I have a 40-foot push up pole (4 sections) that I
>>want to use to support a
>>small VHF/UHF ground plane and the center of an HF
>>inverted "V". This is a
>>semi-permanent installation for about a year. I
>>would like to minimize
>>concrete work, etc. but want to do what's necessary
>>to have adequate guying,
>>etc. to make it through a Midwestern winter and
>>summer of high winds, etc.
>>There are two options for installation location. One
>>is against the side of a
>>two-story house, the other is totally free standing.
>>Web searches haven't turned up much in the way of
>>etc. Anyone with experience to share?
>>See: http://www.mscomputer.com for "Self Supporting
>>Towers", "Wireless Weather Stations", and lot's
>>more. Call Toll Free, 1-800-333-9041 with any
>>questions and ask for Sherman, W2FLA.
>>TowerTalk mailing list
>Do you Yahoo!?
>Yahoo! Calendar - Free online calendar with sync to Outlook(TM).
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>TowerTalk mailing list