No, I think it would be independent of that. But I have to think a bit to come
up with the analytical basis.
On Wed, 29 Jan 2025 12:49:46 -0700, David Gilbert <ab7echo@gmail.com> wrote:
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@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
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