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KENWOOD TH-21A
Expanded RF 140 to 159 Mhz
1. Disconnect the battery and antenna.
2. Remove Knobs, antenna nut ring and plastic top
3. Remove front panel.
4. Locate switch unit (PCB X41-1590-00) This unit has the Vol.SQL etc.
5. Cut trace between R1 and R4 , R5
6. Install a jumper from the common point of R11 , R5 and 5C to the corner
of the tone switch.
7. Install a 1N914 diode and 48K resistor from the center top PIN of the
tone switch to the end of resistor R1. (R1 was cut in step 5).
Note: Cathode end of the diode goes to the tone switch top center pin.
Cathode end of diode has the line.
8. Adjust L10, L11, L12, L13, TC1, TC2, TC3 for maximum upper frequency
range.
9. Reassemble the radio.
10. Depress the tone switch to receive from 140 to 149 Mhz
Tone switch off for 150 t0 159 Mhz.