20
Operation
SeaBat UI - User Manual
Figure 4-5
Gain
The sonar system utilizes a Time-Varied Gain (TVG) by applying a
variable gain to the signal, based upon the formula :
Receiver Gain = 2 α R
km
+ Sp log R
m
+ G
Where:
α
= Absorption loss in dB/km
Sp
= Spreading loss coefficient
R
km
= Range in kilometers
R
m
= Range in meters
G
= Extra gain as set in the Control pane
For more information about this formula see Absorption (page 27) and
Spreading (page 27).
For some sonar systems the gain can be switched to the Fixed mode.
The normal mode is TVG and Fixed mode can be used for very short
ranges (<10m).
4.2.4 Pulse Length
The pulse length setting allows the operator to change the pulse length of
the transmitted signal.
Figure 4-6
Pulse Length
For a given power setting, a narrower pulse length will provide a higher
resolution at a shorter range. A wider pulse length will provide better
range but a lower resolution image.
In certain conditions, for example in turbid waters, the narrower pulse
length may not operate well. In such circumstances, the wider pulse
length may give better short-range performance. This may also be
achieved by changing from higher to lower frequency operation.
4.2.5 Gate
The operator is able to switch on/off the required gate mode(s). By default
they are switched off. If selected the Gate mode button is highlighted.
Figure 4-7
Gate modes with Depth gate selected (highlighted)
There are three gate modes:
Depth
Range
Adaptive
