Icom IC-251A Instruction Manual page 18

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TUNING CONTROL
Rotating the Tuning Knob clockwise increases the frequency; turning it counterclockwise
decreases the frequency in 100Hz steps in the USB, LSB and CW modes and in 5KHz steps in the
FM mode. The smaller vernier marks on the knob represent 100Hz (5KHz in the FM mode).
When you reach 145.999.9 in the SSB or CW modes, or 145.995.0 in the FM mode, turning the
Tuning Control Knob clockwise will bring the operating frequency to 144.000.0, the lowest edge,
and you can continue increasing the frequency from there by continuing to rotate the Knob
clockwise. The VFO endless system functions in the same way when decreasing the frequency
from 144.000.0, and will prevent you from inadvertently operating out of the amateur radio band.
(IC251A : 145.999.9 and 144.000.0 should be read 148.199.9 and 143.800.0).
When the MODE Select Switch is set to the "FM" position from any other mode, the last two
digits of the display frequency are designed to show "0.0", and the frequency is shifted in 5KHz
steps by rotating the Tuning Control. If 5KHz-step frequency shift with the last two digits other |
than "0.0" is desired, set the dial using the following procedure.
The TS Switch must be OFF.
Set the VFO Switch to "A", and the MODE Select Switch to ''USB".
By rotating the Tuning-Control, set the last two digits on the display at the frequency you desire.
Set the VFO Switch to "'B" and then the MODE Select Switch to "FM".
Set the VFO Switch to "A".
- This completes the setting so that the frequency is shifted in 5KHz steps with the desired figures
in the last two digits of the operating frequency. To reset the last two digits to ''0.0'', push the
TS Button twice.
If the knob is too loose or too stiff for comforatble use, you can adjust the torque by tightening or
loosening the brake adjustment screw accessable from underneath the set.
Brake Adjustment
The following instructions should be used to adjust the tension of the Tuning Knob.
Brake Adjustment screw