[TowerTalk] Antenna Survival in Severe WX

[Bill Tippett]

Hi All!

        I just got power back after almost 1 week without due to two
severe back-to-back ice storms here in North Carolina.  I would like to
share my experience from here and Colorado in the hopes it may save your
antennas in severe weather conditions.

Case 1 - Survival in high winds only:

        Align your booms in the direction of the wind with the reflector
facing the wind direction...i.e. if the wind is from the West, point the
antennas East.  I speak from personal experience with a KLM 3 el 40 and
5 el 20 at 150' with no major damage in 11 years surviving many Colorado
Chinook winds over 100 MPH and two over 140 MPH (unfortunately my house
did not survive one of those and lost a chimney which was blown into our
family room!)  This case is also easiest on the rotator. 

Case 2 - Survival in wind AND severe icing:

        If you expect severe icing WITH wind, align your antennas
(before you lose power!) with the tips into the wind...i.e. if the wind
is from the North, point the antennas East.  This will minimize ice
build-up on the elements which are smaller and probably not supported
by a truss like your boom.  It will also minimize the tendency of the 
elements to mechanically self-resonate if they are broadside to the
wind.  In Colorado, I learned this the hard way and watched several
monobanders self-destruct because I left the booms into the wind, 
mistakenly following the Case 1 scenario above, and then lost power
without the ability to turn the antennas.

        A very visible demonstration of the tendency for ice to build
more severely on elements broadside to wind can be seen on Beverages.
My only Beverages to survive the latest storm were those that ran roughly
longitudinally in the wind direction.  Fortunately I had no major damage
with the recent storm but thought my experience might be useful to some.

                                                73,  Bill  W4ZV  


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