Raymarine DSM250, Owner'S Handbook Manual

Page: 78 / 122

5-18 DSM250 Digital Sounder Module
4. To adjust the shift, press the appropriate
SHIFT
soft key: use the up
soft key to select a shallower shift, use the down soft key to select
a deeper shift. The image window is shifted up by the selected
amount. Pressing the
SHIFT
keys sets the range to
MANUAL
.
5. Press
ENTER
to return to the default display.
Hunt Mode
The DSM250 features a digital “Hunt mode” that automatically
searches for the bottom while the sounder is in Auto Range. If
bottom cannot be determined while
AUTO RANGE
is selected, the
DSM250 pings the last known depth, and then incrementally
increases the ping depth to a maximum value determined by the
transducer type (see
Table 5-3 ) until the bottom is found. If bot-
tom is not found, the sounder returns to the original depth and
repeats the process.
If
AUTO FREQUENCY
is also selected (see Selecting the Frequency
on page 5-19 ) when the sounder completes the auto range hunt
process, the process is repeated in the other frequency. If
MANUAL
FREQUENCY
is selected, hunt mode only continues in the selected
frequency. This process continues until bottom is detected or you
switch to manual range mode.
The maximum depth to which Hunt mode searches is determined
by the high power output of the transducer, as follows:
For example, let’s say a DSM250 with a 1000 W transducer is set for
auto range & auto frequency and bottom is currently detected at 500
ft using 200 kHz. The bottom signal becomes lost, so the sounder
switches to Hunt mode. Pinging begins at 500 ft using 200 kHz and
increments to 1500 ft. If bottom is not detected, the sounder switches
to 50 kHz, repeats pinging at 500 ft, and increments up to a maxi-
mum of 5000 ft. If bottom is still not detected, the DSM250 returns
to 500 ft using 200 kHz to continue the process.
Table 5-3: Maximum Depths for Hunt Mode
200 kHz 50 kHz
600 W 1000 ft (400 m) 3000 (1000 m)
1000 W 1500 ft (500 m) 5000 (1700 m)