vhfgp.nec

zip contains tool for Antenna Modelling with examples

CM VHF Ground Plane, converted with 4nec2 on 29-mrt-06 14:37
CM 	VHFGP
CM This is a pretty ordinary VHF ground plane. For an
CM interesting exercise, add a wire extending downward from
CM the junction of the radials to simulate the outside of a
CM coax feedline. With the wire a half wavelength long, you'll
CM notice significant pattern distortion caused by current
CM induced on the new wire. Various lengths, open or connected
CM to ground, will cause different results. You can simulate
CM addition of "current" (or "choke") baluns by adding loads
CM of about 500-1000 ohms to the new wire.
CE
SY freq=146			' Design frequency.
sy len=0.233	'0.24
sy ang=48.6	'45
SY dl=0.25*sin(ang), dz=0.25*cos(ang)
GW 1 6 0 0 5 0   dl  5-dz  5e-4
GW 2 6 0 0 5 dl  0   5-dz  5e-4
GW 3 6 0 0 5 0   -dl 5-dz  5e-4
GW 4 6 0 0 5 -dl 0   5-dz  5e-4
GW 5 5 0 0 5 0   0   5+len 5e-4

'GW 6 50 0 0 0 0   0   5     5e-4	'Coax

GS 0 0 299.8/freq		' All in WL.
GE 1
EX 6 5 1 0 1 0
'GN -1
GN 3 0 0 0 13 .005
FR 0 1 0 0 146 0
EN