User's Manual

16
DTX-142 ALIGNMENT PROCEDURE
An authorized RF service technician must perform test and alignment of the DTX-142. Do not attempt
service of the DTX-142 if not completely familiar with frequency synthesized radio operation.
RECOMMENDED TEST EQUIPMENT
1) 0 to +15 VDC, 1A current-limited power supply 3) Oscilloscope
2) RF Communications Test with: 4) VTVM or DMM
- FM Deviation Meter
- RF Wattmeter 5) RITRON PC Programming Kit
- Frequency Counter
- SINAD Measuring Device
RADIO PREPARATION
1) Remove the DTX-142 from case.
2) Connect the FM communications test set to the antenna connector.
3) Connect RITRON programming cable to radio and PC.
4) Apply 12.5 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 and TX frequencies in both channels.
8) Select a DCS tone of 071 for TX on both channels. This will be used to set the “balance” pot R304.
9) Set the transmitter to wideband deviation.
10) Program the radio with these parameters.
REFERENCE FREQUENCY AND TX POWER
The DTX-142 is preset at the factory for 5 watts in high power and 2 watts in low power. If you need to
change or readjust do the following:
1) Make sure that the unit is at room temperature (approximately +25° C)
2) Set the RF communications test set to the transmit mode.
3) Select low edge channel on channel select inputs CS2, CS1 and CS0.
4) Make sure the Hi/low power pin 5 is ungrounded. This selects high power.
5) Ground /PTT pin 14 of J301 to transmit.
6) Transmitter frequency error should be less than +/- 100 Hz.
7) Adjust the trimmer cap on the rectangular reference frequency oscillator Y301 if not within specs.
8) Adjust the power pot R222 to give 5 watts (+/- 0.3)
9) Confirm the upper edge frequency produces the same results.
10) If upper edge power is too high turn L201 clockwise to reduce and counter clockwise to increase.
11) Check low edge power again. Readjust L201 to balance band edge powers.