12
3) Sweep timing
This adjustment ensures proper r adar
performance, especiall y on short ranges. The
radar measures the time requi red for a
transmitted echo to travel to the targ et and
return to the source. The received echo
appears on the display based on t his time. Thus,
at the instant the transmitter is fi red, the sweep
should start from the center of the di splay
(sometimes called sweep origin.)
A trigger pulse generated in the dis play unit
goes to the antenna unit through the antenna
cable to trigger the transm itter (magnetron).
The time taken by the signal to travel up to the
antenna unit varies, depending largel y on the
length of signal cable. Duri ng this period the
display unit should wait before s tarting the
sweep. When the display unit i s not adjusted
correctly, the echoes from a strai ght 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.
Correct Target pushed
inward Target pushed
outward
Figure 24 Examples of improper and
correct sweep timings
1. Transmit the radar on 0.125 or 0.5 nm
range and adjust the sensitivity and STC.
2. Visually select a straight echo (harbor wall,
straight pier).
3. Press and for 10 seconds to show the
installation menu.
4. Select ADJ TMG on the menu.
SEL MENU
BY ▲
/
▼ KEY
1. ADJ HDG
2. ADJ TMG
TOTAL ON TIME
00000 : 00
TOTAL TX TIME
00000 : 00
IDENTIFY STRAIGHT TARGET
SUCH AS BREAKWATER. MAKE
ITS ECHO STRAIGHT ON SCREEN
USING KEYS.
TUNE
▲
▲
/
3. NM /KM
Figure 25 Installation menu, ADJ TMG selected
4. While looking at the target s elected at step
2, straighten it by pressing if it is pulled
inward, or if it is pushed outward.
4) Unit of range measurement for VRM and cursor
The unit of range measurement for the VRM
and the cursor may be selected to nautical m ile
or kilometers as follows:
1. Select NM/KM on the menu.
3. NM /KM
SEL MENU
BY ▲
/▼ KEY
1. ADJ HDG
2. ADJ TMG
TOTAL ON TIME
00000 : 00
TOTAL TX TIME
00000 : 00
<RANGE UNIT>
PRESS KEYS TO SELECT
NAUTICAL MILE OR KILOMETER
AS THE UNIT OF RANGE.
TUNE
▲
▲
/
Figure 26 Installation menu, NM/KM selected
2. Select unit of range desired.
3. Press the [MENU] key to close the
installation menu.