Matt didn't say 12 inches above the tower ... he said 12 feet ... and I
totally disagree with the rest of your comments. Assuming the tower
itself is capable of handling the antenna load (taking into account the
leverage of the mast), it is FAR FAR cheaper to simply use a mast rated
for the job than it is to install another tower or rotate the existing
tower.
I have a 70 foot heavy duty freestanding tower with 15 feet of 1/4 inch
thick 2 inch diameter chromalloy mast sticking out of the top of the
tower. The mast holds up an OB16-3 three feet above the tower and an
OB2-40 about twelve feet above the tower. Those are decently large
antennas ... MUCH larger than a 10m monobander. I regularly (almost
daily in the spring) get wind gusts on this southern Arizona hillside
that exceed 80 mph and I've measured them as high as 100 mph (strong
enough to strip the gears on my Prosistel PST-61D rotator) and the mast
has held up fine after six years of that ordeal. A similar mast would
cost just over $500 last I checked, which is considerably cheaper and
simpler than what you propose.
Dave AB7E
On 2/12/2014 1:12 PM, Dan Cisson wrote:
Matt....an opinion only... You are really not accomplishing much if
anything...You say you are guying the mast 12 inches out the top of
the tower ?? All you are doing at this point is asking a storm to bend
the mast above the guy ring...Long masts are asking for trouble, there
is a heck of a lot of leverage on the top of a long mast in high
winds...You could possibly be OK with a 6 meter beam atop the mast, or
a 2 meter beam, its a gamble !!. But if you put up an antenna that is
much bigger than a 10 meter yagi,, you are asking for PROBLEMS !!I
have took down too many of them in my days of tower work. Other
alternatives are another tower(probally not an option for most hams)..
or fixed antennas down the tower...It is expensive, but you can rotate
the complete tower!! I would check with antenna manufactures and see
how close you can stack their antenna to other antennas on the same mast.
It will be interesting to see what other opinions you get here on TT..
Good Luck, and be CAREFUL !! ,,Dan N4GNR
----- Original Message ----- From: "Matt" <bluewaterpro@yahoo.com>
To: <towertalk@contesting.com>
Sent: Wednesday, February 12, 2014 2:45 PM
Subject: [TowerTalk] Guying mast above rotor
I know the subject line sounds dumb,, but I have 15' of mast above my
tower and live in South Florida. Read on...
Im thinking of putting a guy ring at about 12' above the top of the
tower, and, only in event of a severe storm, attach 3 guy wires,
which would be anchored in concrete, the cables sitting on the
ground, affixing them to the collar in event of storm.
I've also thought of having short guy wires permanently mounted on
the guy ring collar, with the short guy cables running down the mast
to the top of the tower. Then i could climb up and attach the guy
wires, if needed. No need for a bucket truck.
I think this would provide additional survivability to the mast in
heavy wind
Any thoughts on this? Good idea, bad?
Thanks/73
Matt w1mbb
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