coax.nec

zip contains tool for Antenna Modelling with examples

CM Dipole with coaxial feedline.
CM
CM This file shows how you how you can model a coaxial feed
CM To do so, use the default Nec TL card to model the feed
CM and in parallel with this feed, model a wire with the
CM same physical length as the feedline. The length specified
CM in the TL card equals the physical lenght / the velocity 
CM factor for the coax. Use 'Currents->Magnitude' on the
CM 'Geometry (F3)' window and use Page-up/down to magnify the
CM current on the 'outer' of the coax. Click on the wire 
CM resembling the Coax to see how large the current is for
CM the specified power input. Although the coax is fully
CM symmetrical with respect to the antenna the current on
CM the outer wire can cause trouble with RFI if the feedline
CM is very close to a TV/telephone-line or electrical house 
CE wiring.

SY hgh=10			' Antenne height
sy len=5.11			' Half wire length

GW	1	20	0	-len	hgh	0	-0.03	hgh	1.026e-3	' Left wire
GW	2	1	0	-0.03	hgh	0	0.03	hgh	1.026e-3	' Mid TL segment
GW	3	20	0	0.03	hgh	0	len	hgh	1.026e-3	' Right wire
GW	4	1	0	-0.03	1	0	0.03	1	1.026e-3	' V-src segment
GW	5	40	0	0.03	hgh	0	0.03	1	1.026e-3	' Outer coax wire
GE	0

SY Z0=50, Vf=0.66		' Coax Z0 and Vf
SY Tlen=hgh-1		' Physical length
SY Elen=Tlen/Vf		' Electrical length

TL	2	1	4	1	Z0	Elen

EX	6	4	1	0	1	0
GN	2	0	0	0	20	0.0303
FR	0	1	0	0	14	0
EN