19. You are directed to install your tactical radio station near an urban
area airport. You decide to use vertically polarized antennas at this
site in order to eliminate interference caused by--
a.
FM radio stations, electrical machinery, and tall buildings.
b.
tall buildings, the television station, and FM radio stations.
c.
aircraft, television stations, and FM radio stations.
d.
aircraft, tall buildings, and commercial radio broadcasts.
20. When compared with a horizontally
polarized
antenna,
the vertical
antenna is better for--
a.
propagating sky wave transmissions.
b.
rejecting enemy electronic jamming transmissions.
c.
rejecting electronic interference from friendly transmissions.
d.
receiving transmissions from all directions.
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ANSWERS:
16.
F
17.
T
18.
T
19.
c.
20.
d.
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9.
RECEIVING ANTENNAS.
a. Vertical antennas.
Vertically mounted receiving antennas accept
radio signals equally from all directions. Because of this omnidirectional
characteristic, vertical antennas are best for most tactical operations.
Radios operating in highly mobile situations must receive signals from many
directions. (All vehicle-mounted ratios use the vertically mounted quarter-
wave whip antenna.)
b. Horizontal antennas.
Horizontally mounted antennas accept radio
signals from all directions other than the two directions in direct line
with the ends of the antenna.
Thus, interference can be reduced (or
eliminated) by positioning the receiving antenna so that one end of the
antenna points directly at the interfering station.
c. Directivity.
Radio
communication
for
field
artillery
is
satisfactory when the receiver is within range of the transmitter--when the
signal at the receiver is strong enough to override unwanted signals and
noise. Occasionally, an operator may find that the station he is trying to
reach is out of range.
There are several things that can be done to
overcome this problem.
Increase transmission power.
Change to continuous-wave signals (AM radios so equipped).
Reposition transmitting antenna (Fig 11).
15
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