Antenna bandwidth 13.941- 14.504 MHz.
SWR 1.0:1.0 at 14.207 MHz. The Helix Antenna was fed by 75- Ohm
coaxial cable in 15.82- meter length.
Design: PVC Pipe in diameter 110- mm and length 68- cm was used
for the antenna. Antenna was wound by copper tube with OD 6- mm.
Photos are shown design of the antenna. Lower part of the antenna
contains 10 ¾ - turns and wound above the tube. Middle
part of the antenna contains 35.5 turns. The coil is inside of
the tube. Upper part of the antenna contains 7 turns and wound
above the pipe. At the 20 meter Band the inner wire of the coaxial
cable is connected to 5 turn (from the cold end) and ground of
the coaxial cable is connected to the beginning of the spiral.
Antenna should be placed in 50 cm above a surface.
Band 15 meter: The antenna being tuned to 20- meters should be matched
at 15 – meter Band.
Band 10 meter: Antenna may be tuned at 10- meter Band. Ground of the
coaxial cable is connected to 6 turn (from the cold end) and inner
wire of the coaxial cable is connected through inductor (OD- 9-
mm, 7 turns of 1,0- mm (18- AWG) copper wire) to 5th turn from
the cold end.