At the test the antenna (Fig.3) was installed at 4.0- meters
mast. Antenna was fed by 500- Ohm two- wire symmetrical line.
At the antenna terminal one wire of the line was connected to
the helical antenna, second wire was lived free. At the transmitter
terminal one wire was connected to "Antenna" second
one to the "Ground." Antenna was tested at 20- meters
Practice shows that it is wise to use a square rod
for a helical antenna because coils sitting well at the form.
Diameter/side of the square should be 1/50- 1/200 from the length
of the Helical Antenna. Wires should be protected from atmospheric
by strong paint. Wire for winding a helical should be have large
diameter as possible but coils of helical should not short to
Current distribution on the antenna may be found with
the help of neon bulb. After that the tuning of the antenna was
made by the current (checked by antenna milli- ampere- meter)
going to the antenna.
1 shows data for the Helical antenna for 20-40-80-160
meters. The antennas were made on a square rod with size 3- cm
by wire in 2.5- mm OD. Gap between turns was 7.5- mm.