190-01182-02
GTR 225/GNC 255 TSO Installation Manual
Rev. F
Page B-7
B.2.4.1.2 Set Active COM Frequency and Transceiver Function.
This message is used to set the Active COM frequency as well as the COM transceiver function.
Message format:
“C” ..........................Message class. This is a GTR/GNC COM message.
“00”.........................Message identifier.
mk ...........................Active COMM frequency:
m = desired frequency in MHz in hexadecimal, where m = desired frequency -
30h, with desired frequency in range of 118 to 136 MHz.
k = desired frequency in kHz, where k = (desired frequency / 25 kHz) + 30h,
with desired frequency in range of 000 to 975 kHz in 25 kHz steps.
a...............................Transceiver function: N = normal, M = monitor, 0 = unchanged.
o ..............................8.33 kHz offset: (ASCII) 0 = 25 kHz frequency (.000); 1 = first 8.33 kHz
channel offset (.005); 2 = second 8.33 kHz channel offset (.010); 3 = third
8.33 kHz channel offset (.015)
Example message:
$PGRMC00G4N0<chksm><CR><LF>
This example command would set the active COM frequency to 119.100 MHz and place the COMM radio
in Normal receive mode. This is interpreted by noting that the ASCII “G” corresponds with 47h, +30h =
77h, converted to decimal equals 119 for the MHz portion. The kHz portion converts ASCII “4” to 34h, -
30h yields 4h, x 25 kHz steps = 100 kHz, with no 8.33 kHz channel offsets.
NOTE
The GTR/GNC will check input frequencies for validity. An RS-232 serial error message
output will be generated if the frequency is invalid, or an 8.33 kHz frequency is requested
when the GTR/GNC is in 25 kHz channel spacing mode.
NOTE
The GTR/GNC will ignore this message while transmitting on the active COM frequency.
