TM 11-5985-284-15
of the null may increase to 30 or 40O. The center
(2) Positions 1, 2, 3, and 4 provide increas-
ing and marked differences in attenua-
of the null (or area) is the correct bearing.
d. Sensing. Because there are two nulls, the
tion. The position of least attenuation
null indication does not provide sufficient informa-
that permits sense and bearing determi-
tion for the operator to determine whether the
nation should be used. operation in
transmitting source is in front of, or behind, the
ATTENUATOR position 4 is not nor-
loop antenna. To find the actual direction of the
mally used except in the immediate vicin-
transmitting source, a null is detected, the sense
ity of the transmitting station (within
whip antenna is extended, and the loop antenna is
100 to 200 yards depending on the ter-
turned sideways to the transmitting signal.
rain). An accurate sense indication will
When the signal is loudest in the receiver, the
be difficult, to obtain in this position, but
SIGNAL MAX arrow on the top of the case (fig.
this condition should not present any
2-3) will point in the direction of (sense) the
operating difficulties since the general di-
transmitting signal.
rection of travel has been previously
e. Homing. Homing is the procedure of detect-
established and the null bearing should
ing a transmitting station and approaching it.
be sufficient for transmitter location.
The general procedure is as follows:
(1) Find the null.
2-8. Operation
(2) Determine the sense and take a bearing
The operating procedure of Antenna AT-1082/
on the transmitting station as indicated
PRC for homing-in on a modulated or unmodu-
by the SIGNAL MAX arrow on the top
lated carrier is described below. On the receiver,
of the case (fig. 2-3).
the greatest, signal response (maximum signal)
(3) When the direction of the transmitting
for a modulated carrier is indicated by a loud
station is determined, the sense whip an-
audio output ; for an unmodulated carrier, the
tenna is retracted, the loop antenna is
indication is indicated by maximum receiver
turned broadside to the transmitting sta-
quieting.
tion, and the null indication is detected on
a. Preliminary.
the receiver. If the null is particularly
(1) Check to see that the AT-1082/PRC is
broad, rotate the loop antenna back and
connected to the receiver (para 2-3).
forth a few times. Select the center of
Remove all other antennas from the re-
the null, and proceed on a line through
ceiver. Set the ATTENUATOR con-
the center of the null until the transmit-
trol to 0.
ting station is reached.
(2) On the receiver, tune to the operating
(4) As the transmitter is approached, succes-
frequency, set the volume control for
sive bearings can be taken with increased
maximum loudness, and set the squelch
accuracy because of the narrowing null
control to off when there is such a
area which results from increased signal
provision.
strength.
f. Attenuation.
b. Procedure.
Caution: Whenever the loop antenna is not
(1) Unfold the loop antenna, and set the
in use, keep the ATTENUATOR switch at 0.
BANDSWITCH and FINE TUNE con-
trols to the positions that are closest to
(1) Very strong signals may have a tendency
the frequency setting on the receiver.
to obscure the null and sense indication.
For example, to tune to 45.80 MHz, set
In general, such signals will be found
the BANDSWITCH control to 40 and
close to the transmitter. If the hearings
the FINE TUNE control to 5.
are obscured and the transmitter cannot
be seen, advance the ATTENUATOR
(2) Hold the AT-1082/PRC vertically (fig.
switch to position 1, 2, 3, or 4 to reduce
2-2), and rotate it clockwise and counter-
the signal strength to the point, where
clockwise for maximum signal indication
the null becomes clear.
on the receiver. Readjust the FINE
Previous Page
