Onwa Marine Electronics KR-12X8 - Manual (Page 65)

Adjusting sweep timing(Adjustment range:0.000~4.266nm)
This adjustment ensures proper radar performance, especially on short ranges.
The radar measures the time required for a transmitted 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 display 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 display unit should wait before
starting the sweep. When the display 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.
(1) Correct (2) Target pushed
inward (3) Target pushed
outward
Figure 6-18 Examples of improper and correct sweep timing
1.
2.
3.
Transmit on the shortest range and confirm that the [GAIN] and [STC]
controls are properly adjusted.
Visually select a target which forms straight line (harbor wall, straight pier).
Select
"Sweep Timing Adjustment" on the installation setup menu and
press the [ACQ/ENTER] key. The message appears.
[ Sweep Timing Adjustment ]
Use omnipad to staighten
Target and press ENTER key.
Correction 0.000 nm
<Press MENU for inst setup>
4. Operate the omnipad to straighten the target selected at step 2, and then press
the [ACQ/ENTER] key.
Figure 6-19 Sweep timing adjustment message
58