[TowerTalk] beam antenna truss

[K8RI]

On 12/23/2012 8:30 PM, Patrick Greenlee wrote:
> Don't use nylon as it is too stretchy.  Don't use polypropylene as it
> lacks UV resistance (Good water ski rope though) Dacron is a good very
> low stretch rope, preferably treated for UV resistance but you can put a
> sleeve over it like cut from a throwaway garden hose .  You can cover
> the knots with black silicone caulk and prevent the knots from
> weathering.  Phillystran is an excellent material but...don't clamp it
> or tie it in a knot.  Use the approved methods of terminating it: 1. the
> Chinese finger grabber type grips or the 2. the two part catalyzed
> potting system. Not really practical to use the grips on a really short
> piece of Phillystran.  some argue against a conductive material but
> commercial antennas use conductive material often. If you have the
> ability to do the math or perform the tests you can find out what the
> effect of a conductive material is.

For a relatively light weight boom I'd not hesitate to use clamps, but 
remember you will lose about 50% of the rated strength.  I use 3 clamps 
  and a minimum torque, or clamping force for the small Phillystran.  I 
would prefer the potted ends when using larger cable and heavier booms. 
  OTOH with long booms and lower frequencies the "Big Grip" ends should 
not create a problem.  Multiple trusses for the long boom.  I don't 
think they would be a problem on 20, but won't offer a guarantee.  <:-))

73

Roger (K8RI)


>
> 73 Patrick AF5CK
>
>
> -----Original Message----- From: Cqtestk4xs at aol.com
> Sent: Sunday, December 23, 2012 7:10 PM
> To: TOWERTALK at contesting.com
> Subject: Re: [TowerTalk] beam antenna truss
>
>
> The cheapest is to use is wire.  However, this can cause interaction
> accord
> ing to some, with the Yagi.
>
> Many use rope.  On my M2 antennas Dacron is used, fastened to the boom  by
> mean of an eyebolt through the boom.
>
> Some guys use Phillystran in the same fashion.
>
> Bill KH7XS/K4XS
>
> In a message dated 12/24/2012 12:50:36 A.M. Coordinated Universal Ti,
> w1dxh at aol.com writes:
>
>
> Looking for info on best way to truss a long boom yagi. What is  the best
> material to use? How to secure to boom etc. Thanks for  help.
>
> 73,
> Steve  W1DXH
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