TM 11-5985-284-15
DIRECT SUPPORT MAINTENANCE
Section I. FUNCTIONING OF EQUIPMENT
intercepts remains constant. Typical
4-1. Scope
field strength patterns for vertical and
This chapter contains instructions for direct
horizontal antennas are illustrated in A
support maintenance of Antenna AT-1082/PRC.
and B, figure 4-1.
It includes instructions appropriate for trouble-
shooting, testing, alining, repairing the equipment
and replacing maintenance parts by repairmen at
this maintenance category. It also lists the as-
sociated tools, materials, and test equipments. De-
tailed functions of the AT-1082/PRC are covered
in paragraphs 4-2 through 4-4.
4-2. Antennas
a. General. During transmission, a radiofre-
quency (RF) current in a conductor produces an
electromagnetic field that is radiated into space.
This field consists of electric and magnetic fields
that are at right angles to each other. The plane
parallel to the mutually perpendicular lines of
electric and magnetic flux is called the wavefront.
The wave travels in a direction at right angles to
the wavefront.
b. Receiving Antennas.
(1) If the radiated electromagnetic field cuts
a conductor, current is induced into that
conductor. The received current varies
in accordance with the variations of the
electromagnetic field. Therefore, a vari-
ation of the current in a radiating an-
tenna causes a similar varying current in
a conductor at a distant location.
(2) Antennas receive more energy in some
positions than they do in others. This
directivity is due to the fact that received
a. General. Since fundamental half-wave an-
energy depends on the amount of radiated
tennas possess directional characteristics, it is pos-
field that is cut by the antenna. A hori-
zontal antenna receives maximum energy
sible to determine the direction from which a radio
signal is being received. This determination is
when its vertical plane is parallel to the
plane of the wavefront because maximum
made by rotating the receiving antenna about an
interception occurs in this position. A
axis that is perpendicular to the direction of the
vertical antenna has the same reception
signal and observing the changes in received sig-
nal strength. However, as can be seen from the
strength from all horizontal directions
because the amount of radio field that it
radiation pattern in A, figure 4-1, the directional
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