System Operation
3.4.3 TxPwr
This menu selection allows the operator to increase, or decrease, the amount of
power (acoustic energy) transmitted into the water. The selections are OFF, and
power settings of OFF, 1 through 7, and FULL. Each increment is approximately
3dB. FULL yields a Source Level of approximately 210dB re 1
µ
Pa @ 1m with the
standard stick projector. The optional Extended Range (ER) projector, the level 8
output power increases to 220dB re 1
µ
Pa @ 1m.
3.4.4 TxPulse
The transmit pulse width selection allows the operator to change the pulse width
of the transmitted signal. For a given power setting, the narrower the pulse width,
the higher the degree of resolution that can be obtained; but the range capability
will suffer. A longer pulse width increases the average power of the transmit
pulse and increases the range but decreases the resolution.
The pulse widths available are from 21
µ
s to 225
µ
s in increments of approxi-
mately 4
µ
s. A pulse width of 75
µ
s is typical for most applications. The minimum
recommended pulse width is 33
µ
s.
3.4.5 RxGain
This menu item allows the operator to select the amount of receiver gain applied
to the returned sonar signal. RxGain has two independent settings; TVG and
FIXED. TVG has a range of 1 to 45 in 1dB steps while FIXED gain is a nonlinear
scale.
3.4.6 GainMode
The gain mode menu selection provides the operator with a the ability to apply
different type of gain to the received signal. The gain modes available are:
FIXED
:
This mode applies a fixed (does not vary with time) gain to the re-
turned signal. It is normally only used for very short range opera-
tion (less than 10 meters).
TVG
:
The Time Varied Gain mode applies a variable gain to the re-
turned signal, based upon the formula:
Receiver gain = 2
α
R + Sp log R + G
Where:
α
= Absorption loss in dB/km
R = Range in meters
Sp = Spreading loss coefficient
G = Receiver gain
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SeaBat 8101 Operator's Manual
3-6
Version 3.02
