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

[Matt Lovewell]

Guy,

I am surprised at your findings.  Is it your opinion that unstripped thhn is a no-go for in-ground radials as well?  Would you please share "the method"

Thanks,

Matt
W0MLD

> On Dec 25, 2016, at 12:50 AM, Guy Olinger <k2av at contesting.com> wrote:
> 
> 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
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk