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[TowerTalk] rope in elements

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Subject: [TowerTalk] rope in elements
From: (Tom Rauch)
Date: Thu, 29 Mar 2001 04:14:37 -0500
> When I put up my 90 foot tower a number of years ago, I stacked a 5
> element 15 and 5 element 10 Hygain Yagis. I did not put ropes in the
> elements. We have a fairly consistent breeze off of the gulf here, but
> it isn't really windy. I had immediate problems with the tips on the
> elements breaking on the 10 meter yagi. I was amazed and irritated
> about the element breakage on these new antennas. I called Hygain and
> they shipped me new elements. I replaced the elements and put rope in
> each. Within 6 months, I had three elements broken again...rope
> hanging out the ends! 

Like all resonant circuits, it's a matter of Q. 

What kind of rope did you use? You really must use a soft loosely 
woven rope that still has some mass, or dampening is not optimal. 
Laying a stiff rope or a hard rope inside the element won't help 
much, if at all.

As for the people who say the "design the elements so they don't 
vibrate and break", please tell me where I can find details on how to 
design an element that way. Better still, tell me what you did to 
have that design.

I'd be very interested is seeing the calculation for wind causing 
vibration, or even for element mechanical resonances. Certainly 
someone who designs an element not to fail from vibration would 
have that data, or could explain the process.

73, Tom W8JI 

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