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

>From the desk of Keith Lysiak <KLysiak_at_swri.edu>

Chuck,

        A while back I tried modelling a variety of twin lead and coax
cable with air dielectrics using NEC4. Both of these worked very well
for me. But when I tried a variety of "insulated wires" as dielectric
shieldings I could not get things to work out well. Your results
sound familiar but it has been a while and I do not have the results
handy. I have included some thoughts from 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.

End of Message
Received on Mon Oct 18 1999 - 15:32:10 EDT