Uniden PC 122, PRO 640 & PRO 810 Clarifier Mod

These radios use a lower cost chassis and you can just squeak 5 KHz down from them using a 5.6 µh chock in series with the varactor diode D23.

The following instructions will open and increase the clarifier range:

  • Remove D25
  • Jump D24
  • Lift the ground side of D23 and install a 5.6µh choke from the open lead of the diode to ground.
  • With a volt meter find +8 volts on the clarifier control and cut that trace. Make sure nothing else is connected to this potentiometer contact.
  • Connect the open terminal of the clarifier control to + 8 volts constant (IC4 pin 1).
  • Jumper the other side of the clarifier control to ground.
  • Set the clarifier to the 3 O’clock position.
  • Connect a frequency counter to TP3.
  • In AM adjust L16 to 16.4900 MHz.
  • In USB adjust L17 to 16.4925 MHz.
  • In LSB adjust L18 to 16.4875 MHz.

The President AR144 and Cobra 146GTL have similar circuits and the above instructions are adaptable to them.

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