[TowerTalk] UV and WX deterioration of THHN insulation,

Roger (K8RI) on TT K8RI-on-TowerTalk at tm.net
Mon Jan 2 19:20:54 EST 2017


My center fed slopers on 75 and 40 as well as the 160 half sloper are 
under considerable tension as the half waves have to support the chokes 
and coax, while remaining as straight as possible.   I'd guesstimate 
it's well over 100#. The lower end of the 75 m sloper is anchored to a 
relatively large tree trunk Using 5/16ths Dacron rope at both ends. The 
high end  rope is about 100' long.  It runs from the antenna through a 
pulley at the 95' level on the 45G, then down where it's tied off at the 
4' level. That is more than enough to compensate for any movement of the 
1.5' dia tree trunk at the 6' level.   The sloper to the NE has the same 
length  at the tower end, (3/16ths rope) but only abt 5' to the forged 
eye lagbolt at the tree trunk.

73,  Roger (K8RI)

On 1/1/2017 12:48 AM, Jim Thomson wrote:
> Date: Sat, 31 Dec 2016 20:55:15 -0800
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] UV and WX deterioration of THHN insulation,
> and effects
>
> Yes, it has nothing to do with the insulation. In an earlier post, I
> noted that I every two years, I have to circumcise my 80/40 JA fan that
> uses #10 stranded THHN for the 80M element. It's up about 130 ft, fed
> with RG11, so a lot of tension on it. I've changed to wire on the other
> 80/40 fan to the bare #8 solid stretched to #9.
>
> 73, Jim K9YC
>
> ##  I have not had any stretch issues with RW-90  in 10 gauge, but that was
> for slopers and inverted vees etc, with no weight on them.   The insulation on
> RW-90 is very thick stuff.  I  have also used it in 8 gauge.  10 gauge  alumoweld
> is  stupid strong stuff, doesnt stretch.
>
> ###  IF  degraded THHN wire actually increases  RF resistance, then the
> input Z to the dipole, etc should also increase by a bunch.
>
> Jim   VE7RF




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