Mat Eshpeter wrote:
> I have searched the archives but have not been able to find an answer to my
> question.
>
> I am building a cabin on top of a tall ridge in West Virginia. I am
> interested in putting up a tower next spring (between 55' and 72') near the
> peak of the ridge and am trying to make a decision between crank-up vs fixed.
> My concerns, in order, are 1) lightning, 2) ongoing maintenance, 3)
> difficulty of installation.
>
>
I've never worried a great deal about lightning. The tower here
http://www.rogerhalstead.com/ham_files/Tower26.htm with the large array
on top http://www.rogerhalstead.com/ham_files/Tower29.htm has been stuck
many times. It was averaging 3 verified strikes a year for the first 5
years, then a dry spell which ended about two weeks ago with #16. The
first year, before the ground system was finished I did lose one
computer. After finishing up the ground system, which includes over
600' of bare #2 copper, 32 or 33 8' ground rods, the grounded bulkhead
entrance for the cables from the tower as well as grounding the shield
on all coax at the top and bottom of the tower, there has been no
further damage. From the top of the tower where I'm working (in the
second link) I'm above everything within about 1 1/2 miles. The top of
the mast with the 144 and 440 antennas on a cross boom is 30 feet above me.
The old tower http://www.rogerhalstead.com/ham_files/tower9.htm which
had a repeater antenna above the tribander for some years only took one
hit, but it destroyed the repeater antenna and blew out the 7/8" Heliax
about 20' down from the top. It also removed all of the water proofing
from every connector at the top of the tower which resulted in water
running through the 9913, out of my 2-meter rig, and onto the desk about
15 minutes later. With that in mind I'd certainly put in a substantial
ground system.
> Regarding lightning, my land is at the crest of a hill. From this hilltop
> location, I am aftaid that my tower would be an ideal target for lightning.
> The hill is 1600' above sea level, and many hundreds of feet higher than any
> nearby hills. There are some tall trees within a couple hundred feet, but a
> fixed tower @ 70' is making me nervous. A crankup tower, when fully
> retracted, would be less than 25', perhaps offering less of a magnet for
> lighting strikes. But given that the towers will be well grounded, I am not
> sure if there would be much of a difference given that lightning would have
> the option of 100' trees or a conductive tower at 25'
> (crankup) / 70' (fixed). I would appreciate hearing from anyone with a tower
> installed on top of a hill. Would the 45' height difference between 70' fixed
> vs 25' retracted crankup have any meaningful effect on the probability of
> lightning strikes?
>
Intuitively I'd say yes, but as either of them will pretty much be the
highest spot there probably will be little difference. However I have no
real information to back that up.
When we lived near Farwell MI (bout 50 miles NW of here) I had a 50'
tower near the top of the highest spot in the area (30 to 40 miles) with
a tri-bander and a pair of vertically polarized 14 L KLMs on 2-meters on
top, some 24-25 years ago. It was never struck as far as I know and I
didn't see any evidence when we took it down. OTOH I saw the 200'
repeater tower about 500 yards East, get struck many times.
73
Roger (K8RI)
> Regarding maintenance, I have concerns about the crankup and associated motor
> drive and limit switches properly functioning a few years down the road, not
> to mention the cables and pulleys. I am looking at US Tower and Tashjian
> crankups. The fixed tower would be a 70' Rohn 45G guyed twice for each of the
> three anchors. From everything I have read about guyed Rohn towers, other
> than annual inspection, there isn't any maintenance for quite a few years.
> The crankup motor drive would be used quite often -- every time I head up to
> the cabin to operate.When leaving the cabin, the crankup would be lowered to
> its fully retracted height. This equates to approximately 3 or 4
> raising/lowering cycles each month.
>
> Regarding difficulty of installation, the crankups look to be more effort,
> requiring heavy equipment to lift the tower off of the delivery truck, a
> crane to mount the antennas, and about triple or more the excavation and
> concrete. The fixed tower requires more land but I have 20+ acres to work
> with.
>
> My other options are 1) don't install a tower, or 2) put the tower lower on
> the hillside in order to lower the probability of lightning strikes; this
> would completely block my shot to the west and hurt my shot to the north and
> south;my shot to the east would remain excellent.
>
> The antenna that I am looking at is an M2 7-10-30LP8, but I am far from
> decided. The option of "no tower" is not really an option; after 20+ years, I
> feel it is time to talk to the DX.
>
> Opinions appreciated, especially those with hilltop tower experience in
> lightning-prone locations.
>
>
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