[TowerTalk] Ice storm experience with antennas this week

Robert Shohet kq2m@mags.net
Thu, 14 Dec 2000 19:10:52 -0500


 Hi Tom,

 Glad that your antennas survived ok!

 In Southwestern CT I am in one of the iciest places in the country - that
 is - it is usually cold enough to snow but because I am close enough to
Long
 Island Sound and the Atlantic Ocean, snow is usually not the outcome. (I
 have had freezing rain with temps as low as 6 F!)  I had icing in SS Phone,
 CQWW SSB, CQWWCW and some in the 10 meter contest and got a real serious
 ice-storm today.  This has NOT been a good year!

 You make very good points.  Overbuilding antennas, guy wires, towers, etc.
 is essential to give your antennas and towers every chance to survive.  ALL
 my yagis are double hose-clamped, double nutted (with Loctite Blue) and the
 boom sections have little sheet metal screws in them to prevent rotation.
 Each antenna element has a plastic element cap with a small hole to allow
 for drainage, ditto with the larger caps on the boom.  Likewise, every
 element has rope inside to dampen vibration and each element hoseclamp is
 taped to prevent against it catching in a guy wire, tree branch or flying
 object in a windstorm.  Of course, the use of ice-clips on the guy wires is
 another good (and expensive)  precaution.

 The only problem with double hoseclamping and rope (inside the element) to
 dampen vibration is that it provides more surface area for ice to build up
 and more weight inside the element.  But I believe that this is more than
 offset by reduced wind fatigue and reduced likelihood of nuts & hoseclamps
 loosening up on the elements.

 I can tell you that the Hygain and Cushcraft antennas that I use have
 withstood winds in excess of 120 mph at my qth in a violent thunderstorm in
 May and 90 mph on Monday.  I have no doubt that some of them would not be
 here now but for the extra work and precautions that I have taken.  Of
 course if we get a serious ice-storm with 50 mph winds I am sure that I
will
 be picking pieces of aluminum off the ground anyway.

 Wire antennas (PVC insulation) and good quality rope should not break in an
 ice storm, but they will break the branches off the trees.  Always keep in
 mind that some branches, which are strategically "placed", may not be there
 in the aftermath of an ice storm and a big wire antenna, although the wire
 antenna will be fine.   So it pays to lower the wire antennas somewhat (and
 reduce tension) BEFORE an ice storm so that the trees and branches will
 survive as well.

 The first part of antenna survival is good planning and building.  The rest
 is just luck.  But the better the planning and construction, the less luck
 is needed and the more storms that antenna(s) and tower can survive.

 73

 Bob KQ2M



> ----- Original Message -----
> From: Tom Whiteside <n5tw@igg-tx.net>
> To: <towertalk@contesting.com>
> Sent: Thursday, December 14, 2000 4:28 PM
> Subject: [TowerTalk] Ice storm experience with antennas this week
>
>
> > We are just thawing out from an ice storm in central Texas - not as bad
as
> > one 4 years ago but the second worst one I've seen and sufficient to
knock
> > down power lines and break many large tree limbs - sigh...   Thought
some
> > data on how the beams faired might be of interest...    Forgive me if
you
> > deal with ice storms frequently in your area but places like here, it is
> > news.
> >
> > The beams in use here are of various pedigrees - we have large M2
antennas
> > for 15 and 20M - the 44.5 foot boom varieties - 3 on each tower.   We
have
> 2
> > Cushcraft XM240 beams and 6 of the Force12 elite monobanders for the 10M
> > tower and for fixed multiplier antennas.    After a night of freezing
> rain,
> > they all looked pathetically wilted with a heavy ice load...   I had
taken
> > advice from this reflector and turned them all 90 degrees off from the
> wind
> > and maybe this helped - dunno.     The droopiest was the F12 EF320 with
> the
> > Cushcraft coming in second.   The great news is that all fully sprung
back
> > when the ice melted...
> >
> > Another observation was that all the wire arrays survived despite heavy
> ice
> > loading.   That dacron rope and flex-weave wire from Davis RF is tough
> stuff
> > and has now lived through 2 of these storms over the last 4 years.    My
> > Beverages were another matter...  One of 4 Beverages survived intact but
> the
> > other 3 could not take the large limbs falling across them and broke...
> > Same thing happened 4 years ago.    The good news is that they are made
> with
> > the insulated version of DavisRF's flexweave and this stuff is virtually
> > unkinkable and will be easy to repair...    I've ended up moving all
these
> > Beverages at least once over the last 4 years and the wire is easy to
work
> > with and is like new...   I highly recommend this stuff...
> >
> > Not affiliated in any way with DavisRF or any of these manufacturers but
> > very pleased with all of them - especially given this latest stress
> test...
> >
> > Tom Whiteside
> > N5TW Georgetown, TX
> >
> >
> > --
> > FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
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> > Problems:                 owner-towertalk@contesting.com
> >
> >
> >
>


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