I have a 150' Rohn 65G tower guyed with 11,200 pound Phillystran and I
have no concerns about guy stretching. The tower feels solid and it has
been up for years at two different QTH's with no issues.
I used Phillystran at my Aruba station. Steel guy cables and grips needed
replacement every four years and the Phillystran was still in excellent
shape when I dismantled the station.
John KK9A
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Rotating tower guying question
From: "StellarCAT" <rxdesign@ssvecnet.com>
Date: Mon, 4 May 2015 08:57:34 -0400
Just as a reference:
I had a 141? rotating R45 tower in AZ ... the guys were attached at about
120?
(top) and out ~105?. I used 1/4? throughout. I used insulators throughout as
well using the values provided in the handbook.
thoughts:
-I stayed with EHS because of the article written by K7NV regarding towers
and
guys and the fact that philly stretches so much more than EHS. That concerned
me greatly.
-Although there is extra labor in adding the insulators I?d say it might
be, as
it was for me at the time, a non-issue as it is a one time adder and not THAT
time consuming. Its not as if you?re getting paid for the hour if you
DIDN?T do
it!
-The values in the handbook... the one thing they don?t seem to take into
account is the shortest length going to the tower ? I believe mine was
like 6?
or something similar ? but it is that x2 (or x3 considering all three) AND
the
width of the tower so for me it seriously interacted with 10 meters, a bit
less
so on 15 and not too much on 20 (had C31?s stacked a foot above 3 guy
points).
It was very noticeable as you rotated and it got worse as you went down the
tower where the angle was getting much worse (approaching the antenna plane).
The last item above was solved by a suggestion from Dave, AB7E. Dave had said
how about clamp on ferrites? I bought some 1/2? ID clamp on ferrites (a $1 ea
for 30 of them surplus) and after adding I believe it was 3 on each of the
the
guy attachment points (about 2? out) the SWR problems went away! I?ve
wondered
since then why others haven?t done this along the whole length (in the
plane of
the antennas).
The middle item above is of course one that an individual has to judge on
their
own. But its not, at least to me, a clear cut choice as my ?spare? time is
mine
to use ? and I?m not going to get paid for using it a different way... I?d
suspect it would be the same for most others.
As for the top one.... K7NV?s analysis seems straight forward ... however
there
are MANY philly installations that have been up for years and I?ve not
heard of
one where a tower fell because the lines stretched so much during high winds
and forced a collapse ... they probably, most assuredly exist ? but I?m sure
you could find that for EHS installations as well (other issues). I have
thought about going with the next size up philly (11,000#) for a length
say 50?
from the tower (of course steel at the tower with the clamp ons) and then EHS
after that to provide much higher strength and much less worry about
stretching
as well as no worries about interaction.
My gut says EHS would outlast philly ? easily ? with UV being the primary
villain for the philly ... but I?ve heard of towers in FL that have been
up now
for 25 years with philly that are still standing ? even to the point where
the
outer coating has been totally degraded away... although that might seem
reassuring one has to couple with that the margins built into a tower
installation. In other words these anecdotal examples are only as good as the
known data. A tower could be, for example, left self supporting for years
IF it
never sees winds over say 50 MPH... it is that (less to much less common)
high
wind event that is going to stress it. So stories of towers lasting for years
don?t mean a great deal overall ? I?d still not sleep well at night
knowing my
tower had visibly degraded philly on it.
Bottom line is I?ll probably stick with EHS and insulators. I?m planning on a
rotating tower ? 140? R55 (anyone have some for sale?! Or rotating
components?)
with 5/16? EHS and insulators.
Gary
K9RX
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