[TowerTalk] EZNEC Question

[David Gilbert]

Given that the field strength of that traveling wave follows current, 
would that mean that the loading effect tracks the current distribution 
of the wire simply because the field strength does?

Dave  AB7E


On 1/29/2025 11:49 AM, Jim Lux wrote:
> well, yes, the "propagation velocity" goes as sqrt(epsilon).  So it 
> might not make a difference where it is - it's not so much whether 
> it's a high voltage or high current part of the transmission 
> line/antenna, it's the traveling wave aspect of the signal as it 
> propagates down the wire.
>
>
>
> On Tue, 28 Jan 2025 12:08:57 -0700, David Gilbert <ab7echo at gmail.com> 
> wrote:
>
> I did some more searching and found a similar discussion on the 4NEC2
> reflector from about 3 years ago.  In it was a link to this article by
> Cebic which seems to indicate that dielectric loading of a conductor
> produces an inductive effect.  If that's the case it makes sense that it
> would have more effect at a current maximum than a voltage maximum.
>
> https://hamwaves.com/wire/doc/Insulated%20Wires:%20The%20NEC-2%20Way.html
>
> I also harkened back to the formula for velocity factor in a coaxial
> transmission line, which is V = 1/sqrt(er), where er = the relative
> permittivity.  That certainly describes the equivalent of an inductive
> effect.
>
> Apparently at age 77 I'm not yet too old to learn ... although that day
> might not be too far off.  ;)
>
> Dave   AB7E
>
> >
> >
> > On Mon, 27 Jan 2025 20:33:55 -0700, David Gilbert wrote:
> >
> > I've been using EZNEC Pro/2 to try to model the effects of dielectric
> > loading on a wire antenna ... specifically a full wave loop on 435 MHz.
> > I split the sides of the loop up into multiple wires (each with multiple
> > segments) so I could individually declare a thick dielectric ... i.e.,
> > insulation in the wires table ...  separately for each portion of the
> > loop.  To my surprise the loading effect seems to be greatest at or near
> > current maximums, not at voltage maximums where I would have presumed
> > the electric field would have the most effect.  This has me greatly 
> puzzled.
> >
> > Any thoughts?
> >
> > Dave   AB7E
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>