[TowerTalk] Antenna positioning in the wind

Kurt Andress ni6w@yagistress.minden.nv.us
Tue, 08 Dec 1998 00:46:02 -0800


 PAUL924@aol.com wrote:

> I would like those of you who have yagi antennas out there to share their
> knowledge
> on this topic.
> What is the correct position for a yagi antenna, in windy conditions, to
> minimize possible damage ?
> a) Point the Director into the wind
> b) Point the Reflector into the wind
> c) Point the element tips into the wind
> Any input from you gentlemen would be appreciated.
> Thanks...Paul   W2JGQ

Hi Paul,

This has certainly been the subject of much conjecture et al on 2 meter
repeaters for years. Fun stuff eh? No doubt everyone has an opinion about it!

The real answer depends on what we are trying to accomplish by orienting the
antenna in the wind.

If we are trying to point it so that the antenna has the best chance of
survival, we need to know which antenna parts are the weak link. Some
antennas have very strong booms and weaker elements. Others are equal. And
then there are those that have weak booms and strong elements (usually the
minority for most short boom commercially available 10-20 meters).

If we are trying to point the antenna to produce the least load on the tower
we may need to do something else.

Unfortunately, the information supplied by most manufacturers doesn't allow
us the opportunity to make the decision on our own. Hygain is the closest to
telling us what we need.
All of the major mfgr's have the software to generate the necessary info.
They are probably trying to figure out how to get to it, but the plain facts
are that they haven't produced the necessary information so we can't
intelligently discuss the subject!

I beat this drum a while back on the reflector to explain the situation and
get everyone to understand it. It then quickly went to sleep and everyone
forgot about it.
Hence, nothing has really changed.
The company you buy your antennas from presents you with a single antenna
area. With the exception of Hygain, we don't have a clue what these numbers
really mean.

Before we attempt to engage in the discussion of where we should point our
antennas, we need to know the following things:

1) The safe windspeed for the elements (antenna pointed into the wind).

2) The projected area of all elements when the antenna is pointed into the
wind.

3) The safe windspeed for the boom (antenna pointed 90 degrees to the wind).

4) The projected area of the boom when antenna is 90 degrees to the wind.


The required information will allow us to decide where to point our antennas.

If we have a hell for stout tower, that is not dangerously overloaded by the
antennas, we will chose the direction that will minimize the chance for
antenna failure.
If we have put too much stuff on the tower, we will chose the direction that
presents the lowest antenna area, thus minimizing the loads on the tower. May
lose a few antennas but that is better than losing the tower!

Until guys like yourself start asking the manufacturers for the necessary
information, we will continue to get a bunch of nonsense that leads everyone
to make ill advised decisions.
The commonly held myths will continue and people will continue to lose
hardware.

Every comment I've read so far on the subject contains shreds of valuable
information and shreds of absolute nonsense. We need to get the 4 basic
values for a Yagi, then we can decide what to do with it when the wind blows.
I figure we'll get what we need in another 15 years. Hope I'm around to see
it!


73, Kurt

--
YagiStress - The Ultimate Software for Yagi Mechanical Design
Visit http://www.freeyellow.com/members3/yagistress/



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