Re: NEC-LIST: Insulating Sheath (IS) command in NEC-4

> Keith Lysiak quoted Jerry Burke on the subject:
>
> Q1) The insulated wire model in NEC-4 assumes a polarization current
> in the dielectric that depends only on the radial E due to charge at
> that point on that wire. When parallel wires are close together it
> probably would not be very accurate. If you put it on only the
> inner conductor then the fields associated with the outer conductor
> wires could propagate in free space. If you put insulation on all
> wires it would (neglecting other accuracy questions) look like round
> sheaths on all wires and not be confined between inner and outer
> conductors. Maybe you could "calibrate" the radius and permittivity
> of the sheath with some numerical experiments. I have not heard of
> anyone trying that.

My watching the standing-wave pattern on the line and adjusting epsr
in the IS command in order to achieve the desired standing-wavelength
seems to be an example of "calibrating the permittivity of the sheath
with some numerical experiments." It worked fine; I just didn't
understand why I got the value of epsr that I did.

Thanks for the info. 73 -Chuck W1HIS
Received on Mon Oct 18 1999 - 15:28:39 EDT