[TowerTalk] UV and WX deterioration of THHN insulation, and effects at RF.

[Edward Mccann]

You can deduce some of the secret stripping sauce from this old post of 0l' Guy from seven years back:

http://lists.contesting.com/_topband/2010-09/msg00110.html

Merry Christmas
AG6CX
Ed McCann
Sausalito 



Sent from my iPhone

> On Dec 25, 2016, at 12:56 AM, Svend Spanget <spanget at gmail.com> wrote:
> 
> Aren't you going to reveal 'the method'?
> 
> \Svend
> Sendt fra min OnePlus One
> 
> Den 25. dec. 2016 09.51 skrev "Guy Olinger" <k2av at contesting.com>:
> 
>> First of all, and most important, a joyful holiday season and a prosperous
>> New Year to all of you.
>> 
>> Now down to microscopic issues that will probably have no bearing on World
>> Peace...
>> 
>> Let's be clear that I stand by my prior statements against using unstripped
>> THHN at RF, respectfully, others' contrary statements notwithstanding.
>> 
>> We have careful measurements. We can't just walk away from measurements. A
>> measurement is a measurement, not an opinion. We're stuck with
>> measurements.
>> 
>> The effect in one case, losses from deteriorated insulation on elevated
>> THHN radials were the same as if one had placed a 15 ohm resistor between
>> the coax center conductor and the vertical wire. ***The owner was unaware
>> and thought everything was fine.*** How this came to light is an involved
>> story.
>> 
>> Someone with a low band dipole in the air using unstripped THHN may be
>> paying quite a penalty, especially if it's been up a long time. It would
>> have developed very slowly, very sneaky. Not like having a branch drop on
>> your antenna and having the SWR suddenly go bonkers.
>> 
>> I find the defense for using UN-stripped THHN outdoors and for RF
>> intriguing. Even more intriguing, stuck with the prospect that THHN might
>> be bad for us, some propose going to a different (less common, more
>> expensive?) THH-something variant hoping for a better insulation lifetime,
>> while admitting the new THH-whatever will probably go down from UV as well,
>> just later. ???????  You're hoping for what advantage from the insulation?
>> 
>> With the single exception being some posters to this reflector, everyone I
>> know locally or have corresponded with, or talked with on the phone on this
>> subject, they all bought a spool of THHN from a Home Depot/Lowes/etc for
>> outdoor antenna wire because it COST LESS, maybe half the price of same AWG
>> from sources that sold it as bare wire.
>> 
>> Likewise if they didn't strip it, the single reason they did not strip it
>> was because it appeared to be a lot of work. Some tried to strip it but had
>> the problem of the knife digging the copper. They had never seen a
>> description of "the method".
>> 
>> It turns out that it is possible to strip 250 feet of THHN in the time it
>> takes to walk the length of the wire, if you use the method. The limiting
>> factor is the distance you have available to stretch it out before you
>> strip it. Everyone who has seen it done, later says it's obvious once
>> you've seen it. Once they have seen it done they all strip the THHN and put
>> up the solid bare wire.
>> 
>> It's impossible to NOT take some hit with still-insulated THHN vs.
>> stripped. If nothing else, they're out for the dielectric loss of the
>> insulation.
>> 
>> Then there are potential gradually increasing losses as the UV deteriorates
>> the material, with clearly proven examples of severe end-stage losses with
>> the UV deterioration.
>> 
>> Happy Holidays everyone, and back to the egg nog.
>> 
>> 73, Guy K2AV
>> _______________________________________________
>> 
>> 
>> 
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