My first helical antenna
was made from a slinky coil (See: http://www.antentop.org/023/UN7FGO%20_023.htm)
. Now I decided make antenna from a good copper wire. The antenna was
my experiment in shortened helical antennas that may be only one
antenna in strictly environment. I choose the 40 meter band as
universal band for day and night propagation.
(You may found information
on Helical HF antennas at: http://www.antentop.org/library/shelf_helical.htm)
For antenna form I used
two plastic tubes in 32- mm (1.25 inch) diameter and in 1 meter
length. Holes were drilled in the distance of 10 and 5 cm from
the tube ends. Screws in diameter 4- mm were inserted in the holes.
Antenna wire was attached to the screw. It was wound 20 meter
of 1- mm (18-AWG) wire on the each tube. Between themselves the
tubes were fixed by other plastic tube in diameter of 20- mm and
in length of 20 cm. The small tube was easy inserted inside of
the 32- mm tubes and may hold them firmly. Box near the antenna
contains balun. Figure 1 shows the antenna design.