Figure 3-8. Receiving Set, Radio AN/PRR-9, antenna loading coil adjustment

n. Remove the ID-1189/PR RCVR OUT- PUT plug from the AN/PRR-9 electronic assembly headset jack. Turn the

AN/PRR-9 receiver control fully counterclockwise to OFF. Loosen the receiver screw holding the receiver electronic

assembly to the RECEIVER ALIGN- MENT receptacle (fig. 3-1). Remove the AN/ PRR-9 electronic assembly from the

RE- CEIVER ALIGNMENT receptacle by carefully pulling it straight out.

o. Replace the AN/PRR-9 electronic assembly into its case. Carefully engage the horn transducer contact pins in the

receptacle of the receiver electronic assembly (TM 11-5820 549-12). Replace and tighten the one retaining screw holding

the horn transducer to the AN/ PRR-9 electronic assembly. Tighten the two retaining screws on the front plate holding the

AN/PRR-9 electronic assembly to the case. Replace the AN/PRR-9 Battery BA405/U. Attach the AN/PRR-9 to a helmet

and place the helmet on an operator's head. The antenna should be vertical with respect to ground. Turn the AN/PRR-9

receiver control fully clockwise, and then counterclockwise, to a comfortable listening level.

p. Insert the ID-1189/PR antenna into the ID-1189/PR RCVR ANT jack (fig. 3-1). Set the ID-1189/PR FUNCTION

switch to RCVR- ANT.

q. Position the operator, with helmet-mounted AN/PRR-4, 3 to 4 feet from the ID-1189/ PR. Set the ID-1189/PR

RCVR TEST SIG. rotary switch so that noise is heard in the receiver horn transducter.

r. Adjust the AN/PRR-9 antenna loading coil (fig. 3-8) for minimum noise. Vary the distance of the AN/PRR-9 from

the ID-1189/ PR, or adjust the ID-1189/PR RECVR TEST SIG. rotary switch to maintain some noise in the AN/PRR-9.

Repeat the AN/PRR-9 antenna loading coil adjustment until no further reduction of noise can be obtained.

Figure 3-8. Receiving Set, Radio AN/PRR-9, antenna loading coil adjustment.

s. Remove the AN/PRR-9 from the helmet, turn the receiver control to OFF, and mark the AN/PRR-9 operating

frequency in the space provided on the side of the AN/PRR-9 identification plate. This completes the alignment

procedure and the AN/PRR-9 is now ready for use on the selected channel frequency. .

3-6. Alignment Chart, Receiving Set,

Radio AN/PRR-9

After becoming familiar with the procedures in paragraph 3-5, the following alignment chart may be used to permit more

rapid AN/ PRR-9 alignment:

Change 2

3-8