Furuno NAVNET 1933C-BB - Manual (Page 50)

3-6
Antenna tuning
Initialize the tuning as follows.
1. Transmit the radar.
2. Open the RADAR SETUP menu, and then select TUNING by the trackball or [ENTER]
knob.
3. Press the A: EDIT soft key to show the setting window.
TUNING
ON
OFF
Tuning setup menu
4. Select ON.
5. Press the [ENTER] knob or C: ENTER soft key to start the auto tuning. After the
adjustment is completed, the message “NOW TUNING” disappears and control returns
to the menu screen automatically.
TIMING ADJUSTMENT
This adjustment ensures proper radar performance, especially on short ranges. The radar
measures the time required for a transmitted echo to travel to the target and return to the
source. The received echo appears on the display based on this time. Thus, at the instant
the transmitter is fired, the sweep should start from the center of the display (sometimes
called sweep origin.)
A trigger pulse generated in the processor unit goes to the antenna unit through the signal
cable to trigger the transmitter (magnetron). The time taken by the signal to travel up to the
antenna unit varies, depending largely on the length of signal cable. During this period the
processor unit should wait before starting the sweep. When the processor unit is not
adjusted correctly, the echoes from a straight local object (for example, a harbor wall or
straight pier) will not appear with straight edges – namely, they will be seen as “pushed out”
or “pulled in” near the picture center. The range of objects will also be incorrectly shown.
(2) Correct (1) Target
pulled (3) Target pushed
outward
Examples of improper and correct sweep timing
1. Transmit on the shortest range and confirm that gain and A/C SEA are properly
adjusted.
2. Visually select a target which forms a straight line (harbor wall, straight piers).
3. Open the RADAR SETUP menu and select TIMING ADJUST.