Figure 39.
Field-expedient ground-plane antenna.
If you expect strong winds, add a rope from the ground plane to a stake in
the ground. A swaying antenna causes the signal to fade in and out.
31. IMPROVISING HORIZONTAL (DOUBLET) ANTENNAS.
The doublet antenna is a
bidirectional, horizontally mounted, half-wave antenna. It consists of two
quarter-wavelength sections on each side of an insulator (Fig 40). For best
operation, it should be suspended as close to one-half wavelength above the
ground as possible. (This depends on the height of the supports.)
a. Construct the antenna.
Step 1.
Determine direction of transmission, and prepare supports
(trees, poles, etc.).
Step 2.
Compute half-wave antenna length, and prepare wire.
Step 3.
Cut the wire in half, and put an insulator on each end
(three insulators--see Figure 40).
Step 4.
Prepare transmission line. Separate the two wires of WD-
1/TT, and attach one wire to each side of the center insulator. (Be
sure the transmission line is long enough to reach to the ground and
then to the radio set.)
Step 5.
Tie rope or wire to the two end insulators, erect the
supports, and hang the antenna. Keep it as level as possible.
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