CM A helix dipole for lora (433MHz) that fits in a soda can
CM Created by Roger Walker, GW6HRU
CM 
CM Arcs and helix are difficult to enter in nec2. They draw at 0,0,0 and are moved using the Coordinate Transformation (GM) command
CM 
CM Inputs
CM Calculated
CM SY CN=CL/(PI*X)		
CM SY CP=((Y-CF)/2)/CN		
CM   Actual length of N turns of a helix is sqrt() Where D is diameter, and H=height
CM 	L=sqrt( (N*PI()*D)^2 + H^2 )
CM So:	L^2=    (N*PI()*D)^2 + H^2 
CM So:	L^2-H^2=(N*PI()*D)^2
CM So:	sqrt(L^2-H^2)=N*PI()*D	=> N*PI()*D=sqrt(L^2-H^2)
CM So: 	N=sqrt(L^2-H^2)/PI()*D
CM GM	{II}	{RP}	{RX}	{RY}	{RZ}	{SX}	{SY}	{SZ}	{ID}
CM GW	{II}	{S}	{X1}	{Y1}	{Z1}	{X1}	{Y1}	{Z1}	{R}
CM GM	{II}	{RP}	{RX}	{RY}	{RZ}	{SX}	{SY}	{SZ}	{ID}
CM GN	3	0	0	0	4	0.003
CM GH 	{ID}	{NS}	{SP}	{HL}	{X1}	{Y1}	{X2}	{Y2}	{R}
CM GM	{II}	{RP}	{RX}	{RY}	{RZ}	{SX}	{SY}	{SZ}	{ID}
CM GM	{II}	{RP}	{RX}	{RY}	{RZ}	{SX}	{SY}	{SZ}	{ID}
CM GM	0	0	0	0	0	0	0	H+CF	0	
CE
SY Y=0.110	'Can height
SY X=0.065	'Can diameter
SY H=1		'Height from ground to bottom of antenna
SY N=1.0	'One wavelength
SY R=0.00035	'Conductor radius 0.35mm = 0.7mm diam
SY S=1.01	'Scale for SWR (allows for wire diameter and proximity to ground)
SY CL=S*299.792458/(4*433.92)	'Adjusted 1/4 wavelength length
SY CF=CL/50			'Feed point = 1/200th wavelength
SY CH=(Y-CF)/2	'Half height with vertical feedpoint
SY CN=sqr(CL^2-CH^2)/(PI*X)	'Fractional number of turns
SY CP=CH/CN	'Pitch based on CN
CM GH 	{ID}	{NS}	{SP}	{HL}	{X1}	{Y1}	{X2}	{Y2}	{R}
GH	11	50	CP	CH	X/2	X/2	X/2	X/2	R	'Draw large helix
CM GM	{II}	{RP}	{RX}	{RY}	{RZ}	{SX}	{SY}	{SZ}	{ID}
GM	1	1	180	0	0	0	0	-CF	11	'Copy 11 (Helix) to -CF (inc by 1, 1 copy=12)
GW	1	1	X/2	0	0	X/2	0	-CF	R	'Vertical feedpoint
GM	0	0	0	0	0	0	0	CH+CF+H	0	'Move all up
GE	0
LD	5	0	0	0	58000000
GN	-1
EK
EX	0	1	1	0	3	0	0	'Feed in 1.1
FR	0	0	0	0	433.92	0
EN