Cobra 142GTL & Uniden Washington Clarifier Mod
This chassis requires the addition of a 5.6ph choke in series with the varactor diode D20 to get any additional slide range from this clarifier. The use of a super diode would give the radio a swing of more than 10 Khz but they seem to be unavailable for now. Adding the choke will give you more than 5 Khz down and 2 Khz up.
The following instructions will open and increase the clarifier range:
- Remove R187
- Remove D36
- Jump D35
- Lift the ground side of D20 and install a [email protected] choke from the open lead of the diode to ground.
- Follow the red wire from the clarifier control and disconnect it from this point then attach it to ground.
- Follow the orange from the clarifier control and disconnect it from this point then attach it to +8 Volts constant (IC4 pin 3).
- Set the clarifier to the 3 O’clock position.
- Connect a frequency counter to TP1 on channel 40.
- In USB adjust CT3 for 35.0075 MHz.
- In LSB adjust L19 for 35.0025 MHz.
- In AM adjust L20 for 35.0050 MHz
The center slot is now at 3 O’clock and 5 KHz down is approximately in the 9 O’clock position. Radios will vary due to the tolerances of all the parts in the circuit and the characteristics of the crystal in the circuit.
If the 142 has been channeled up then the crystal has been changed from an 11.1125 MHz to a 11.3258 MHz part. Depending on the manufacturer of the crystal the radio may slide more or less than the factory unit. Also the center slot position of 3 O’clock may not be able to be obtained.