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Serial Interface Specifications
Apollo SL30 Installation Manual
67
SET ACTIVE VOR/LOC FREQUENCY AND RECEIVER FUNCTION
This message is used to set the active VOR or Localizer frequency as well as the receiver
operating function. The SL30 can detect if the supplied frequency corresponds to a VOR or a
Localizer channel, so this command will work for both types of NAV aids.
Message format:
“V” ................ Message class. This is a VHF NAV message.
“27” ............... Message identifier.
mk.................. Active VOR/LOC frequency:
m = desired frequency in MHz in hexadecimal, where m = desired
frequency - 30h, with desired frequency in range of 108 to 117 MHz.
k = desired frequency in kHz, where k = (desired frequency / 25 kHz) +
30h, with desired frequency in range of 000 to 950 kHz in 50 kHz steps, or
the even numbers from 30h to 56h.
a..................... Receiver function: N = normal; M = monitor; 0 = unchanged.
Example message:
$PMRRV27E4N<chksm><CR><LF>
This example command would set the active VOR frequency to 117.100 MHz. This can be
interpreted by noting that the ASCII ‘E’ corresponds with 45h, +30h = 75h, converted to decimal
equals 117 for the MHz portion of the command. The kHz portion converts ASCII ‘4’ to 34h, -
30h = 4h, x25 kHz steps = 100 kHz. This command would also set the receiver function to
normal, leaving the standby channel inactive.
Note: The SL30 will check input frequencies for validity. An RS-232 serial error message
output will be generated if the frequency is invalid.
SET STANDBY VOR/LOC FREQUENCY AND RECEIVER FUNCTION
This message is used to set the standby VOR or Localizer frequency as well as the receiver
operating function. The SL30 can detect if the supplied frequency corresponds to a VOR or a
Localizer channel, so this command will work for both types of NAV aids.
Message format:
“V” ................ Message class. This is a VHF NAV message.
“28” ............... Message identifier.
mk.................. Standby VOR/LOC frequency:
m = desired frequency in MHz in hexadecimal, where m = desired
frequency - 30h, with desired frequency in range of 108 to 117 MHz.
k = desired frequency in kHz, where k = (desired frequency / 25 kHz) +
30h, with desired frequency in range of 000 to 975 kHz in 50 kHz steps, or
the even numbers from 30h to 56h.
a..................... Receiver function: N = normal; M = monitor; 0 = unchanged.