CM LoRa/LoRaWAN tutorial 45
CM https://www.mobilefish.com/developer/lorawan/lorawan_quickguide_tutorial.html
CM https://www.mobilefish.com/download/lora/normal_mode_helical_868mhz_professor_technology_4nec2.nec.txt
CM Helix 868MHz (14.75 turns) over perfect ground
CM Helix starts 4mm above ground
CM Helix diameter = 4mm 
CM Helix turn space = 1.2mm
CM Helix wire diameter = 1mm
CM Wire with length=4mm and diameter=1 mm added between helix and ground
CM Excitation at bottom of this wire
CM --------
CM Number of segments helix nsh = 55
CM Helix diameter dh = 4mm
CM Helix radius rh = dh / 2 = 0.002
CM Helix wire diameter d = 1mm
CM Helix wire radius r = d/2 = 0.0005
CM Number of turns n = 14.75
CM Spacing between turns space = 1.2 mm
CM Total length of the helix len =  n * space = 14.75 * 0.0012 = 0.0177
CM Radius in x at helix bottom = rh
CM Radius in y at helix bottom = rh
CM Radius in x at helix top = rh
CM Radius in y at helix top = rh
CM Move helix xz = 4 mm 
CM Number of segments wire nsw = 10
CM Frequency freq = 868.0 MHz
CM -----
CE
SY nsh=55
SY dh=0.004
SY rh=dh/2
SY d=0.001
SY r=d/2
SY n=14.75
SY space=0.0012
SY len=n*space
SY xz=0.004
SY nsw=1
SY freq=868.0
GH	1	nsh	space	len	rh	rh	rh	rh	r
GM	0	0	0	0	0	0	0	xz	0
GW	15	nsw	rh	0	0	rh	0	xz	r
GE	1
GN	1
LD	5	0	0	0	58000000
EK
EX	0	15	1	0	1	0	0	0
FR	0	0	0	0	freq	0
EN