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

[Jan Erik Holm]

Well, I was going to back out of this but I guess it´s
difficult.
This is the second time Steve point this out, I thought
everybody had gotten the picture.
This is more or less the way I have designed the elements
and it workes just fine.
I have also done a few other things that might help but
that was due to other reasons.
On yagis for 20 and 40 I have dubble tubing in the middle,
I have ice and snow loading and also wanted to have elements
that didn´t droop all that much. Forexample on my 40 yagi
elements droop about 1 meter (3.5 feet or so) from center
to the end, atleas I am satisfied with the design.
Also another idea that I have is to make the end piece as
long as possible to get as little weight far from element
center as possible.
Also I use quite stiff (hard) aluminum, that might also help.
So what Steve is saying is just about how I did it, or more
exact I taper less agressive to further away from element
I get.
Either I been lucky or something but they dont vibrate and
some antennas been up there for more then 20 years so I must
have done something right.

73 Jim SM2EKM

PS: Forgot one thing, I use tubing that fit exact in to each
other, some dimensions has to be grinded/polished down a tenth
of a millimeter or so to fit but the fit must be as tight as
possible. I then use stainless screws to lock them in place,
two screws at each joint except for tiny 10m yagi´s I just
use one.
Now my finger is thired!

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K7LXC at aol.com wrote:
> In a message dated 8/11/03 3:48:35 AM Pacific Daylight Time, k1ttt at arrl.net 
> writes:
> 
> 
>>How do you design elements so they don't vibrate?
> 
> 
>     Design them ala' F12 with an aggressive taper schedule (start big and 
> taper rapidly) so that the elements are not the same size for their entire 
> length. That will eliminate the low windspeed vibrations. 
> 
> Cheers,
> Steve     K7LXC
> TOWER TECH 
>