Set the transmitter meter switch (Item 8) to 12 CH PCM or 24 CH PCM. The
position of this switch will depend upon the type of PCM system. For example
a low capacity system (6-12 channels) using a TD-660/G multiplexer will
require a switch setting of 12 CH PCM. When operating in a medium
capacity system (12-24 channels) place the meter switch at 24 CH PCM.
After setting the switch to 12 or 24 CH PCM, adjust transmitter INPUT
control (Item 7) until the transmitter meter reads in the green band.
The adjustment can only be made if the correct input is being obtained from
the associated multiplex equipment. Also to prevent overmodulating the
transmitter, be sure to keep the meter needle near the left side of the green
band while adjusting the INPUT control.
During this portion of the lesson you learned the procedures for tuning the transmitter section of
the AN/GRC-103. You should heed one precaution which is to never apply power to the radio
set before setting the channel controls. You also learned the proper sequence of performing the
steps which will tune the transmitter. You should know the normal indication to expect as each
step is performed. The transmitter tuning steps you have just read should be followed to insure
that the radio set will operate properly and at the authorized frequency.
This completes the procedures for tuning the transmitter section of Radio Set AN/GRC-103.
Proceed to Lesson Exercise 3 when you are sure you understand the tuning procedure and the
content of each step.