Generally speaking, the purchase of those aluminum
tubing derives from the time of availability to purchase this
tubing set for that moment (it was in 1996). Total length turned
out to be nearly 13 meters. It was measured by footsteps :-),
in case of checking my idea it was not necessary to measure it
more precisely! Only in a couple of years, when I was replacing
nylon guy ropes and with the request of my friends, I measured
exact length of the aerial, it turned to be 12.85 meters long
exactly. In fact, the exact length is not critical - matching
network can compensate it. However, it is necessary to bear in
mind, that even small changes in aerial dimensions (see below)
can affect matching network adjustment and even its circuitry
changes, as a result match work can take
more efforts.
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This article is written to share real
results and to simplify tuning, to minimize painful creative researches
while constructing the antenna.
The Design.
5 meters of the lowermost tubing (see fig.1) - 50mm diameter,
further 5 meters 40mm diameter, 2m- 20mm diameter, and 85cm 10mm
diameter tubing. All aluminum tubing, total length 12.85m. 2.85m
from the top end of the mast, between 40mm and 20mm tubing, 4
folded capacitive loading 3mm copper wires 1.4 meters long are
connected to the mast. Free ends of the wires terminated by insulators
to which nylon guy ropes fasten the mast to the ground plane.
The basic unit construction of the mast along with ceramic insulator
is clear from the fig.2. It stands on a steel 10mm ball, it helps much to withstand wind loads.
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