Specifications

Table Of Contents
MAINTENANCE
Page 129 MRC-565 Packet Data Radio Operations & Maintenance
7.3.1 CMU Adjustments
There are two calibration commands required to set up a CMU to make the radio portion
function properly. These adjustments are set up and saved in the factory or repair center and
require the use of calibrated RF test equipment. These commands are not to be used at the
installation site. A special password sequence must be used to save a new value to any of the
parameters. For troubleshooting purposes, these values can be overwritten on a temporary basis
without the password sequence.
The following values are stored in EEPROM, and are not changed in any operational
circumstance, including factory default command or loading a new operating system. Use the
following commands to view and change these parameters.
CAL Prints out the current cal values
CALRAND Returns value for use in saving CAL parameters
Specific CAL parameter commands:
1. CAL, FREQCAL,nnn Calibrates the freq of the 19.2MHz TCXO
2. CAL, ADCGAIN,nnn Calibrates the ADC1 (J2) rx sig strength, default 47
It’s a good idea to measure and record the 19.2 MHZ Reference Oscillator (TCXO) . Connect a
scope probe connected to TP and plugged into the BNC connector of a counter with a stable
clock reference (<1 PPM) to make this measurement. The oscillators must be within +/- 2PPM
of the desired frequency of 19.20 MHZ. AT 19.2 MHz this is about +/- 5 Hz. If any frequency is
off by more than 5 Hz, you must calibrate it with the following command:
CAL, FREQCAL,nnn
Change nnn around the value 510 to achieve the desired results.
The RSSI values for the receiver can be adjusted by connecting a calibrated signal generator to
each receiver input and the typing MM to read the value the values in DB. You should adjust
the RSSI value at an input level of -106 DBM at the receiver input. At this level MM should
read -106.
You can calibrate the readings by connecting a signal generator to RX Input at J1 and using the
following commands to adjust the gain number.
CAL, ADCGAIN,nnn Calibrates the ADC rx sig strength, default 47
The other cal parameters should not be changed.