[TowerTalk] XHHW wire

[Richard (Rick) Karlquist]

On 2/19/2020 10:08 AM, Steve Bookout wrote:

> Can anyone comment on the difference in the insulating material?   PVC 
> vs ???   And, maybe the difference in the dielectric constant f/u/w EZNEC?
> 
> 73 de Steve, NR4M
> 

When I built my open wire line with XHHW, I assumed the dielectric
constant was about the same as 99% of the types of plastic:  2.2.
The modeling said that I would have to increase the spacing about 10%
vs bare wire in order to maintain 450 ohms characteristic impedance.
When I measured the line, it was very close to 450 ohms, so I guess
that was about right.

Wire insulation is in the volume where the fields are highest.
Thus, even though the vast majority of the dielectric space is air, the
insulation has a noticeable effect.  Way more than a casual
thought experiment would suggest.

Rick N6RK