Jerry Obermeier wrote:
> Hi everyone,
>
> I want to place a grounded 25' metallic mast on the peak of my house
> as a center support for wire antennas. I would like to use a relatively
> thin (but sufficiently strong) gage of phyllistran or dacron rope to guy
> the mast rather than using wire cable. The top of the mast will be up
> about 55', which is higher than I've been able to raise antenna wires
> between trees in the past, so I expect I'm increasing my odds for a
> lightening hit.
> It seems to me if lightening did hit this mast, wet phyllistran or
> dacron guys might fail by melting if they conduct even a small percentage
> of the current surge. Could this happen? Has this happened? Or can I depend
> on a proper mast ground to safely conduct enough energy to spare such guys?
>
> TNX,
> Jerry, KB9ICE
Jerry,Phyllistran cable is made with aramid (Kevlar Tm type) synthetic fiber.
Aramid fiber is notoriously hygroscopic. This means that it has an affinity for
water. It's molecular structure is such that it provides natural sites for
water molecules to attach themselves. Water is plasticizer for almost any other
material.
As a plasticizer water softens and usually weakens the other material.
This is why the aramid cable suppliers strongly advise us to seal off the
exposed ends of the cable.
If you want non-conducting guys, use the aramid cable, because it can be sealed
at the ends and the jacket has low moisture permeability. The dacron rope can't
be sealed.
The nature of your mast ground path will control how desireable the guys are to
lightning. Poor ground path makes wet guys attractive. A good path should work.
Try a 2"-3" wide copper strap from mast-to-earth ground system. Ground system
is the subject of a plethora of previous posts.
73, Kurt
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