11
DR-142 ALIGNMENT PROCEDURE
An authorized RF service technician must perform test and alignment of the DR-142. Do not attempt
service of the DR-142 if not completely familiar with frequency synthesized radio operation.
RECOMMENDED TEST EQUIPMENT
1) 0 to +15 VDC, 0.5 A current-limited power supply
3) Oscilloscope
2) RF Communications Test with:
4) VTVM or DMM
- Frequency Counter
- SINAD Measuring Device
5) RITRON PC Programming Kit
RADIO PREPARATION
1) Solder a coaxial cable to the antenna port.
2) Connect the FM communications test set to the antenna connector.
3) Connect RITRON programming cable to radio and PC.
4) Apply 8 to 15 VDC to the red wire with the black to ground.
5) Run RITRON software and read the radio.
6) Program any two channels of your choice for band edge tune up; one to the low side of the operating
band and one to the high side ( Hint: use a bit of an offset from even frequencies to avoid receiver
interference. A good choice is 136.1 and 156.1 MHz for the low split or 154.1 and 174.1 MHz for the high
split.)
7) Type in these RX frequencies in both channels.
8) Program the radio with these parameters.
REFERENCE FREQUENCY
The DR-142 is preset at the factory to be set on frequency. If you need to readjust do the following:
1) Make sure that the unit is at room temperature (approxi25
°
C)
2) Set the RF communications test set to the transmit frequency counter mode.
3) Select low edge channel on channel select inputs CS2, CS1 and CS0.
4) Insert a small insulated antenna loop probe into the access hole of the VCO shield. Make sure not to
short supply.
5) Read the frequency. Frequency read should be 43.65 MHz higher than desired receive frequency.
Error should be less than +/- 100 Hz.
6) Adjust the trimmer cap on the rectangular reference frequency oscillator Y301 if not within specs.
RECEIVER FRONT END TUNNING
The DR-142 receiver is factory tuned for a frequency range of 136 to 156 MHz (low split) or 154 to 174
MHz (high split). If receiver appears to be less sensitive on one of the band edges the front end tuning
coils may need readjustment. Connect a SINAD meter to the SPEAKER output (pin 12). Unsquelch the
audio amp by grounding pin 11. Set the generator to the upper band edge frequency programmed at –
121 dBm with +/- 1.5 kHz deviation for a narrow band and +/- 3.0 kHz for a wide band receiver. Adjust
coil cores L101 and L102 in until SINAD starts to drop. Back off slightly to maintain best SINAD. Now, set
generator to the lowest frequency programmed at –121 dBm. Similar SINAD readings as the high band
edge frequency should be obtained. If not, adjust coils slightly. Recheck high end and balance
performance.
