[TowerTalk] which rope for element anti-vibration

[john at kk9a.com]

I would look into significantly reducing the diameter of the element tubing
and use long Ø3/8 tips.

John KK9A



Paul N1BUG wrote:

Thanks to all who provided input on this question!

Living in an area that gets a lot of ice and sticky snow, I am not a fan 
of spiral wrapping anything around elements. I have observed that even 
small hardware items such as a screw head on an element creates an area 
that does not shed ice or snow nearly as well as a smooth element. I can 
only imagine what would happen with a spiral wrap of material along the 
whole element.

This is the only antenna I have had which seemed to have a vibration 
problem. It was doing it on the other tower for years but seemed to be 
only on rare occasions. After moving to a different tower at the same 
height it was much worse. There must be something different about the 
air flow or mechanical properties of the particular tower involved. I'm 
going to get some cheap nylon or poly rope to put inside the elements 
and see what happens.

Paul N1BUG


On 8/29/22 07:25, Paul N1BUG wrote:
> I'm trying to get a better sense of how the rope in elements to stop 
> vibration thing works. I've read that it works because as the element 
> swings in one direction, the rope slams against the opposite side, 
> providing a counter-force. What confuses me is that I don't understand 
> how the rope is free to move around. Nylon or polypropylene seem to be 
> recommended but those ropes come coiled or folded and they have a memory 
> effect, so they don't lay flat. When  put inside an element, they are 
> going to be pressing against it in multiple places and directions. It 
> seems like that would limit the rope's ability to move to do its job. 
> What am I missing? I have seen braided rope with extremely fine strands 
> that is soft and doesn't have the memory effect. Is that what I should 
> be using?
> 
> My 6 meter yagi was having a problem. The element tips were oscillating 
> at about a ~200 Hz rate, and the tips were moving at least two inches! 
> It took four trips up the tower to rig and get it down. It will take 
> another four climbs to put it back up, and more if it still has a 
> problem and needs to come down again. I'd like to try to get this right 
> on the first try to avoid all that extra climbing. The four foot center 
> section of each element is .750" OD, with .625" tips. Any practical tips 
> or experiences with similar elements would be appreciated.
> 
> Paul N1BUG