IC490A

From: N1HID@K1UGM

                          IC-490A 10MHz UP MODIFICATION
                         _______________________________

PLL,VCO Adjustment:
                   Remove top and bottom covers.Remove PLL unit cover.Remove 
                   four screws on PLL DRIVER board.Take X1 (15.8145MHz) out
                   in the PLL unit and replace with the 16.321MHz crystal.
                   Connect RF voltmeter to R36 in the PLL unit.Adjust L5,L6,
                   L7 coils for maximum level,(Note: Turn L2 counterclockwise
                   about two turns if there is no signal.).Connect voltmeter
                   to D1.Adjust L2 for 4 volts.Remove connector J4 on the RF,
                   YGR unit.Connect RF voltmeter to the cable from the PLL 
                   unit.Adjust C62,C63,C73,L13 caps and coil for maximum level.
                   Set the display for 444,9985MHz.Connect frequency counter to
                   C54.Adjust R6 in the PLL unit for 202,8100MHz.

B.P.F.Adjustment:
                 Connect power meter to the antenna connector.Set the mode
                 switch to FM.Transmit and adjust L19,L20,L21,L22,C67,C74 for
                 maximum output power.Apply RF signal to the antenna connector
                 (RF signal Generator).Adjust L8,L9,L10,and L11 coils for
                 maximum receive sensitivity from 440MHz to 450MHz.

Receiver Adjustment:
                    Apply 445MHz signal to the antenna connector (RF signal 
                    Generator).Adjust L11 and C18 for maximum sensitivity at
                    445.000MHZ.

Transmit Adjustment:
                    Connect power meter to the antenna connector.Add a jumper
                    between R218 and R219.Set mode switch to FM.Put display on
                    445.000MHz.Tranmit.Adjust C74 for maximum power output at
                    445.000MHz.Remove the jumper.Adjust R154 for 10 watts.
                    Adjust R153 for 1.0 watts.