Types of Operation - TM-11-6625-667-120023

TM 11-6625-667-12/NAVAIR 16-30APM-123-1/TO 33A1-3-367-1

2-6. Types of Operation

tioned for horizontal polarization ((4) below) or vertical

polarization ((5) below) depending on the position of the

a. The test set may be operated to perform radiation

aircraft transponder set antenna. The line-of-sight

or nonradiation tests. The difference between the

operations for the radiation and nonradiation tests is

path between the test set and transponder set antenna

the means of coupling RF energy between the test set

must be free of obstructions. This includes parts of the

and transponder set. Free-spacing coupling for radia-

aircraft to which the transponder set antenna is at-

tion tests is performed using an adjustable antenna

tached and nearby objects. Obstructions between the

mounted on the front panel of the test set. Nonradia-

test set and aircraft transponder set antenna will

cause an abnormal loss of transmitted RF power and

tion tests are performed either by direct cable-attenua-

result in an incorrect reject indication. In addition,

tor coupling to the transponder set or by an antenna

nearby objects may cause RF losses by reflecting a por-

test hood for the AT-884/APX-44 type antennas.

tion of the radiated signal so that cancellations occur.

b. For any type of operation, perform the following

Transponder set antenna flush-mounted on top of

procedures:

aircraft may require that the test set be raised above

(1) Preliminary test setup (para 2-7).

ground level. Proceed as follows:

(2) Starting procedure (para 2-8).

(1) Place the test 50 feet 10 from the

(3) Test procedures for Transponder Set being

aircraft transponder set antenna so that obstructions

tested (AN/APX-44, AN/APX-68, AN/APX-72).

are avoided between the teat set and aircraft trans-

(4) Stopping procedure (para 2-11).

ponder set antenna.

2-7. Preliminary Test Setup

(2) Remove the test set cover by releasing its

The following procedures describe the preliminary test

latches.

setup for radiation and nonradiation operation. Before

(3) Position the test set so that the control panel

preceding, unscrew the relief valves counterclockwise

faces up.

(fig. l-l) two turns to release any internal pressure.

(4) Some aircraft transponder set antennas may be

WARNING

located on wheel flaps, or other movable objects, which

Pressure must be released before the cover is

horizontally position the normally vertical polarized

removed or cover may spring up forcibly and

aircraft transponder set antenna. For horizontally

cause serious injury.

a. Radiation Operation The test set must be cor-

polarized aircraft transponder set antennas, the test

set antenna must also be positioned for horizontal

rectly positioned with respect to distance and angle

from the transponder set antenna for proper test

polarization. To position the test set antenna for

horizontal polarization, grasp the antenna handle (fig.

results. Normally, the distance should be approx-

imately 50 feet within line-of-sight of the transponder

2-3) and gently pull up the antenna to disengage it

from a snap latch. Pull the antenna up at the right-

set antenna. The front panel antenna must be posi-

2-5