RE: NEC-LIST: Shorted Stub Modeling

Hi, John,

I have never tried to use the TL card with a large shunt susceptance
at one end but I suspect it would give you problems in a general wire
antenna simulation since it apparently uses a y-parameter equivalent
circuit. The intended use of the TL card appears to be as an element
in a phased array feed structure so you could take into account mutual
impedance of the elements for the pattern, and also estimate the input
impedance.

I have built shorted transmission lines with wires as shown below to
model the quarter wave phase reverser on a colinear array. This also
simulates whatever radiation is done by the shorted stub. If you look
at the structure with necview or NOV.EXE you can see what I mean.

CM
CM HALF-WAVE OVER QUARTER-WAVE 2M VERT
CM approx. INCHES SCALED TO METERS BY GS=.0248
cm accurate actual inches=dimension*.0248/.0254
cm corrected upper length to be .5wl, rather than 1wl
CE
GW 1,80, 0,0,0, 0,0,240, .125
GW 1,10, 0,0,240, 0,20.1,240, .125
GW 1,10, 0,0,240, -20.1,0,240, .125
GW 1,10, 0,0,240, 0,-20.1,240, .125
GW 1,10, 0,0,240, 20.1,0,240, .125
GW 1,10, 0,0,240, 0,0,260.1, .125
GW 1,10, 0,0,260.1, 20.1,0,260.1, .125
GW 1,2, 20.1,0,260.1, 20.35,0,260.35, .125
GW 1,2, 20.35,0,260.35, 20.1,0,260.6, .125
GW 1,10, 20.1,0,260.6, 0,0,260.6, .125
GW 1,20, 0,0,260.6, 0,0,300.7, .125
gs 1 0 .0248
ge 0
GN 0 0 0 0 13 5e-3
ld 5 0 0 0 5.8e7
EX 0 0 121 1 1 0 50
FR 0 1 0 0 147 .5
rp 0 11 11 1000 0 0 9 36
xq
en

73, Paul, AA1LL
http://www.qsl.net/aa1ll

John Yorko wrote:
>
> Has anyone on the list ever modeled a shorted stub transmission line
> in NEC2? I would like to use a shorted stub to load a segment, but it
> doesn't appear that NEC2 will let me merely short the other end of the
> transmission line using the TL card. Is there a way to do this by
> properly setting the shunt admittance parameters?
Received on Wed Feb 16 2000 - 14:37:34 EST