4-4
Radio Programming and Tuning Procedures
4.4
Transmitter Tuning
The following sub-sections contain the procedures to tune the radio transmitter. These procedures
include:
l
Power Amplifier (PA) Bias Tuning
l
Battery Threshold Tuning
l
Reference Oscillator Warp
l
DAC Tuning (LowBand radios only)
l
Transmit Power Tuning
l
Power Amplifier (PA) Voltage Limit Tuning (VHF 1-25W and UHF 1-25W LDMOS radios only)
l
Modulation Balance Attenuation
l
VCO Attenuation
l
DTMF Deviation
l
MDC1200 Deviation
4.4.1 Power Amplifier (PA) Bias Tuning
Perform the PA Bias tuning procedure as follows:
1.
Under the
Tx Align
menu, select
PA Bias
, and then
High Power
.
2.
Measure/read the DC current drawn from the radio (varies from radio to radio). This value should
typically range from 100-700mA. Record this value as
X
.
3.
Press
Toggle Bias
button for the first bias to enable the PA bias softpot.
4.
Increase softpot value to obtain
Y
until
Y - X
is within the range given for PA current in Table 4-3.
5.
Press
Toggle Bias
for the first bias again to disable the PA bias softpot.
6.
Repeat Steps 5-7 for the remaining
Toggle Bias
buttons.
7.
Program the bias softpot values into the radio by pressing the
Program
button.
8.
Exit the PA bias high power function.
Note: 1. If using the regulated power supply RLN4510 to measure the current drawn by
the radio, remember that the current meter terminals only measure the voltage
drop across a 0.1ohm shunt resistor. Calculate the actual current being drawn
by the radio by dividing the voltage drop across the resistor by 0.1. (V= I*R).
2. Tuning must be performed only for High Power. The tuning screen will show up to
three Toggle Bias buttons numbered 1, 2 and 3. Tuning must be started with the
lowest bias number and continued until all bias points have been tuned.
CAUTION: To prevent damage to the PA, ensure that the antenna output is always
terminated into a 50 Ohm load
!
C a u t i o n
Summary of Contents for CDM1250
Page 1: ...CDM Series Professional Series Two Way Mobile Radio Basic Service Manual ...
Page 2: ......
Page 30: ... ...
Page 34: ...2 22 Service Aids Notes ...
Page 60: ...4 18 Radio Programming and Tuning Procedures Notes ...
Page 72: ...6 8 Accessories Notes ...
Page 86: ...7 14 Model Chart and Test Specifications NOTES ...
Page 90: ...Glossary 4 Glossary Notes ...
Page 91: ......