prevent coupling or radiating from the transmission line, make sure
that the feed line is at right angles to the antenna. See figure 82.
Figure 81. Doublet antenna sag.
SAG
APPROXIMATE SIGNAL LOSS
20
0 db
30
-1 db
40
-2.5 db
50
-5 db
60
-16 db
70
-24 db
80
-25+ db
At angles of 20 to 80 from the
horizontal, signal loss can be
expected.
Keep
antenna
as
horizontal as possible.
Figure 82. Doublet feed
APPROXIMATE INCLINATION
line problems.
ANGLE LOSS
ANGLE
LOSS
0 - 40
0 db
50
-1 db
60
-5 db
70 - 80
No statistics
At angles of 45 to 60 from a
very poor
perpendicular
plane
to
the
doublet, up to 5 db antenna gain
can be lost. Keep feed line as
perpendicular
from
antenna
toward earth as possible.
c.
The disadvantage of the doublet is its narrow operating
range.
See figures 83 and 84.
110
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