Manual Tuning - Furuno FAR-2107 Series Service Manual

- Full search
The full search is performed to find the tuning point where the tuning indicator
voltage (TUNE IND) becomes largest within a tuning voltage (TUNE) range
between about 5 V and 25 V. The full search starts by executing [Menu] -> 1 ->
3:TUNE INITIALIZE.
- Small search
The small search is performed to find the tuning point where the tuning indicator
voltage (TUNE IND) becomes largest within a range of +2.5 VDC with the tuning
point obtained in the full search at the center.
The small search is performed as follows:
1. [Menu] -> 1 -> 3:TUNE INITIALIZE is executed, and small searches are
repeated from long pulse to short pulses and respective tuning points are
saved.
2. When operation is switched from ST-BY to TX, two small searches are
repeated based on tuning points of pulse length saved in Step 1. Then the
tuning tracking operation starts.
3. When the pulse length is changed, one small search is performed based on the
tuning points of pulse length saved in Step 1. Then the tracking operation
starts.
- Tuning tracking
The tracking operation is performed every minute.
Tune voltage is changed.

2. Manual tuning

When the operation is changed from the Automatic tuning to the Manual tuning, the
voltage value manually set in the previous time is retrieved. The variable range for it is
5 VDC to 25 VDC. In the Manual tuning, the tuning tracking operation is not performed.
When the operation is changed form the Manual tuning to the Automatic tuning, two
small searches are performed for the pulse length based on the tuning value obtained in
[Menu] -> 1 -> 3:TUNE INITIALIZE.
3. Tuning indicator presentation
Tuning indicator is set at 80% against the maximum TUNE IND voltage at full search.
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7.2 Antenna Unit