Todd,
> The conclusion was that the boom should be normal to the wind for
> minimum torque on the rotator. This is probably not the direction
> which places 'least wind stress' on the tower, however.
Your conclusions are accurate for small yagis - two meters and
above - where the boom represents a larger surface area than the
elements. However, with HF yagis the elements generally represent
the greater area and the yagi will tend to align itself into the
wind.
Where the surface area of the boom is less than that of the elements,
a "boom normal" condition will result in less loading on the tower as
long as the boom remains normal. As soon as the wind begins to
quarter the antenna, the torque will increase significantly.
73,
... Joe, W4TV
On 5/14/2010 12:03 AM, Tod -ID wrote:
> Ken:
>
> K0LR and I made some experiments to see what would be the 'preferred'
> or 'neutral' direction for antenna orientation during a strong wind.
> We did the work back in April of 2002. What we found was a bit
> surprising so I wrote it up in 2005 and it is on my web site. You can
> see the pictures and read the text. We found that there was a
> difference when we oriented the elements vertically rather than
> horizontally.
>
> The write up is at
>
> www.k0to.us/HAM/2Wind%20Torque%20Experiment%20-April%202002.mht
>
> The pictures showing the experiments made with small yagi antennas
> have a flag in the background that 'shows which way the wind is
> blowing'. Since the flag is straight out from the pole it is obvious
> that the experiments were done in a stiff wind.
>
> The conclusion was that the boom should be normal to the wind for
> minimum torque on the rotator. This is probably not the direction
> which places 'least wind stress' on the tower, however.
>
> Tod, K0TO
>
>
>> -----Original Message----- From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of Ken Eigsti
>> Sent: Thursday, May 13, 2010 9:04 PM To: towertalk@contesting.com
>> Subject: [TowerTalk] STEPPIR and Wind Direction
>>
>> I just replaced a HAM IV that was turning my STEPPIR 3 element with
>> the 40/30 add on "trombone". (Brake broke) I am trying to figure
>> out what direction to park the antenna (it's at a seldom used
>> contest location) with regard to the wind? My C39 Force 12 yagi
>> seems to like to be "pointing in the direction of the wind". If
>> wind is from the west, it's pointed east.
>>
>> When the STEPPIR brake broke and started turning in the wind, I
>> noticed that maybe it likes to have the wind blowing 90 deg to
>> which it is pointed. Wind from West, antenna pointed North.
>>
>> Has anyone else had some experience as to the direction of "least
>> resistance" regarding the STEPPIR and wind?
>>
>> I thought there was a STEPPIR reflector but couldn't find it?
>>
>>
>> Thanks Ken W0LSD _______________________________________________
>>
>>
>>
>> _______________________________________________ TowerTalk mailing
>> list TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
>
>
> _______________________________________________ TowerTalk mailing
> list TowerTalk@contesting.com
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>
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