[TowerTalk] Antenna element vibration damping - How

[Jiri Sanda]

Hi all,

concerning the vibration I do have experience that vibration is also 
very dependent on the behavior of the tower.
We had an antenna that behaved fine on one tower for years. When moved 
to other tower it started to vibrate. Placing heavier "damping" rope - 
old 75 Ohm coaxial cable cured the problem completely.
I DO agree with David that heavier damping in no case makes any harm.

To later responses.
Jan - I would like to see some designs that DOES NOT vibrate at all. 
Until now I have not seen such a beast !!!
To kill the vibration with some rope or wire is fairly easy and does not 
represent any significant cost or problem to put in.

I would like to understand how rivets - no rivets can have the smallest 
influence on vibration. With my dummy head I can not see any physical 
reason.
Just according to my experience drilling a hole into the element is very 
bad, but it is another story......

During the years I have had quite a couple of various elements - right 
know I (we - together with OK1RF) maintain close to 100 HF elements.

73 !

Jiri
OK1RI

David Robbins K1TTT wrote:

>Contrary to what others have said... get the heaviest, thickest rope you
>can slide into the element and still have room for it to flop around.  I
>like a tight nylon braid or old hemp/sisal because its heavy, I would
>guess you could also use a flexible wire rope also but have never seen
>it done.  The dampening action is achieved by the rope moving around
>inside the element to absorb the vibration energy.  A rope about 1/2 of
>the ID of the tubing is generally good.  One other thing interesting
>about it is that it is generally most important to have rope in the
>middle of each side of the element... that is, generally the vibration
>is worst about 1/2 way out from the center to the tip of the elements.
>So if you have a choice (like the element is made of 3 pieces on each
>side) put rope in the middle section and maybe the outer one, rope near
>the boom end does much less for vibration.
>
>Depending on the element construction you can hold it in the element
>with either the end cap or the bolts that go through the element to
>either hold it to the boom or to hold sections of it together.
>
>
>David Robbins K1TTT
>e-mail: mailto:k1ttt at arrl.net
>web: http://www.k1ttt.net
>AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> 
>
>  
>
>>-----Original Message-----
>>From: towertalk-bounces at contesting.com [mailto:towertalk-
>>bounces at contesting.com] On Behalf Of VeeAthreePL
>>Sent: Friday, August 08, 2003 17:41
>>To: towertalk at contesting.com
>>Subject: [TowerTalk] Antenna element vibration damping - How
>>
>>I have had read somewhere on this reflector that in order to damp
>>    
>>
>element
>  
>
>>vibration in the wind you have to insert rope inside the elements.
>>I am just about to install my Mosley TA36 with 40M kit and would like
>>    
>>
>to
>  
>
>>install such a modification. How it is done exactly?
>>Thanks
>>73 de Andy - VA3PL
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com  for "Self Supporting Towers",
>>    
>>
>"Wireless
>  
>
>>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041
>>    
>>
>with
>  
>
>>any questions and ask for Sherman, W2FLA.
>>
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>>
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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