[TowerTalk] Re: Re: Antenna element vibration damping - How

[Jan Erik Holm]

Jiri Sanda wrote:
> Hi
> 
> Exactly that is it.
> We have made elements with steep and slow taper. with long and short 
> thick section, light and medium heavy (25-38mm tube in the center of 20m 
> element)......all of them vibrated in "low" winds, "higher" winds 
> usually do not represent significant problem. I have bought the smart 
> book from Jim Leeson with the idea that someone much smarter then myself 
> will produce some scientific method how to eliminate this problem, well 
> his advice on the end is something like: vibration in a low wind is a 
> problem - use some rope, or cable and experiment......
>
Just came to think of one thing. Since I´m using double tubing in the
center it might act like a damper of some kind. Actually the inner tube
goes right thru the other tube and then there are spacers in betwen
to fix a good fit.
However on the 15m and higher bands I just have single tubing and they
don´t vibrate either so whatever........
>
> 
> What I have observed - as said earlier is that if the tower is "sturdy" 
> i.e. does not move in the wind the antennas vibrate less too. I think it 
> is understandable since the movement of the tower gives it's kinetic 
> energy to the elements.... If you have "thin" tower put the antennas as 
> close to the guy-point as possible - it helps a bit for sure.
> 73 !
> 
I have most of my antennas on 2 rotating towers and they aren´t really sturdy
at all. sure in light wind they will not move but when it starts to blow good
they will move a slight bit due to give in the chain drive, also there would
start to be some torque twist in the tower itself.
So this doesn´t go hand in hand with what you have found out Jiri, beats me!
> Jiri
> OK1RI
> 
,