JW Fishers SSS-100K PC Operation And Maintenance Manual page 19

FISH ELECTRONICS
The fish contains a underwater housing that contains the electronics to generate the 1000 watt power pulse to each
transducer; and preamps to amplify the returning echoes received by the transducers. The amplified signals are then
sent to the surface Sonar Processor where they are processed.
Transmit Pulse
From control box
Sonar Processor
Signals To
Sonar Processor
Control Box
The transmit pulse is generated by the Computer. The signal is sent down the tow cable where it triggers the
transmit circuitry in the fish. The transmit circuitry generates the 1000 watt power pulse to each transducer. The
transducer generates the narrow sound beam that travels out away from the side of the fish. Echoes immediately
begin returning from the bottom as the wave continuous to sweep across the bottom.
Fish
Hard Return
#1
10m
The returning echoes strike the transducer which produce the return electrical signals. The signals are amplified by the
preamp and sent up the tow cable to be processed by the "time variable gain" (TVG) circuit in the Sonar Processor.
Signals continue to be received and amplified until the next transmit pulse. The sequence is then repeated.
A
m
p
#1
l
i
t
u
d
e
Transmit pulse
TOW CABLE
The 150' to 500' tow cable is a hollow core polypropylene rope with three electrical cables in the center. One cable is a
six conductor cable which is used for sending the transmit pulse and voltages to the fish. The other two cables are coax's
which are used to send the return echoes, from the preamps in the fish, to the left and right channel TVG circuits in the
Sonar Processor.
Wires To Surface Control Box
Sonar Processor
Transmit
Circuitry
Pre-Amp
Returning Echos
Light Return
No Return Echos (Shadow)
Signal to Sonar Processor
Shadow
Transducer
100 m Range Switch
Acoustic
Medium Return
Wave
100 m
8"
19
Hard Return
#2
#2
Shadow
Next transmit pulse