JW Fishers SSS-100K PC Operation And Maintenance Manual page 16

TRANSDUCERS
The fish contains two transducers (four transducers if SSS-100K/600K model).
Cables To
Transmit And
Pre-amp
Circuits
In Fish
The transducers are hit with a short duration 1000 watt pulse which causes a highly focused sound wave to be
generated from the side face (window) of the transducer. If the transducers are out of water, you can hear the
transducers "snap" as they react to being hit with the high power pulse. If you touch the window, you can feel
the pulse.
Target #1
T
R
A
N
S
D
U
C
E
R
The main center beam is extremely narrow (aprox 1 deg wide ) and has a tremendous amount of power. It is this
main beam that sweeps across the bottom (away from the fish ) at 4800 ft per sec; which makes for high resolution
pictures. Close to the transducer, is a very broad beam which is the result of side lobes. All side scan transducers
have side lobes. Top quality transducers, such as those used in the JW FISHERS Side Scan Sonar, have very
short side lobes which extend a very short distance. Poor quality transducers have long side lobes extending
20-30 % of the total beam length.
The impact of side lobes is that the printed picture will be distorted if the transducer passes very close to a target
(a few feet ). The printout for the above equally sized targets is shown below. The distortion of target #1 is due
to it being in the beams path much longer than it should have been. Target #1 was in the beams path much longer
than the other two targets.
Target #1
Target #2
Right Main Beam (horizontal/top view)
Right Channel Display
Print Head - Right Channel
Target #2
Window
Transducers
Window
4800 fps
Target #3
16
Target #3