Operations Manual

Page 20 RF Technology R50
6 FIELD ALIGNMENT (CALIBRATION) PROCEDURE
6.4 Line Calibration Procedure
R50> cal line
This procedure is used for calibrating the RF RSSI level reading, FM modulation
(deviation) reading. Also this procedure is used to set the 600 Ohm audio line output
level, Noise squelch level and Carrier squelch level. Simply follow the instruction of
the software as bellow:
Attach an RF signal generator to the input.
Set the RF output to 37.5MHz,
and an input level of -110dBm
with a 1kHz tone and 3kHz deviation.
Adjust the Volume Pot until the DIR AUD output
is 388mV.(eqvt to 0dBm into 600 ohms)
Enter <RET> when done.
Set the RF signal generator's output to -60dBm
Enter <RET> when done.
rssi_scale is 0.417dBm/dac step, and rssi offset is -137.500dBm) --- for example
Adjust the Modulation to only 1KHz max deviation
Enter <RET> when done.
deviation_scale is 1.000dBm/dac step, and
deviation offset is .000dBm --- for example
Adjust the Carrier Squelch to the desired level
Enter <RET> when set.
-99.5 --- for example
Enter the Fast Noise Threshold(in dBm):
Enter the Carrier Alarm Threshold(in dBm):
Set the RF generator output to the desired level ( < -105dBm ),
and adjust the N.SQ adjustment counter clockwise
until the squelch opens, thence turn it clockwise
until the noise is muted.
Enter <RET> when done
6.5 The "Reference" Calibration Procedure
R50> cal ref
To compensate for crystal ageing and other parameters that drift, the following
procedure should be performed approximately once per year.
Open the cover of the receiver, find out the test point TP209 on receiver PCB, using a
frequency counter to measure the frequency and follow the instruction as bellow: