Vexilar FL-8SLT - Manual (Page 21)

21
Beam angle has a large effect on the perfor-
mance of your depth finder. There is more to it
than simply area of coverage. The correct beam
angle to use depends entirely on what you are try-
ing to do with your sonar. If you are fishing for
suspended fish then you probably would be very
pleased with the performance of the 19º. However,
if you were going after fish that are hanging right
on the bottom, along a steep drop-off, you would
have better results with the 9º. Here's why;
Dead Zone is an area
within the transducers cone
of sound that is blind to you.
The wider the beam angle the
greater the possible dead
zone. The sonar will mark
bottom as the nearest distance it sees. If you are fish-
ing over a slope, it may see the high side of the slope,
at the edge of the cone, and mark that as bottom.
The fish that are hanging on the bottom in the cen-
ter of the cone will be invisible to you because they
are actually within the bottom signal on your depth
finder. A narrower beam angle will reduce this effect.
Your depth finder puts out a constant amount of power. It does not
matter where you have the gain level set. Gain simply controls how much
you amplify the signal that is bounced off of the bottom. Therefore, a
narrow beam transducer will appear to be much more powerful than a
wide beam transducer. This is because you are putting that same amount
of power into a smaller area. This can be an advantage if you are fishing
in deep water or a detriment if you are fishing shallow. A narrow beam
transducer can be overpowering in shallow water. The use of an S-Cable
will solve this problem, though.
TRANSDUCER BEAM ANGLES VERSES
DIAMETER OF COVERAGE AND PERFORMANCE
Depth 9º 19º
10’ 1.6’ 3.4’
20’ 3.2’ 6.7’
30’ 4.7’ 10.0’
40’ 6.3’ 13.4’
50’ 7.9’ 16.7’
60’ 9.4’ 20.8’
70’ 11.0’ 23.4’
80’ 12.6’ 26.8’
90’ 14.2’ 30.1’
100’ 15.7’ 33.5’
120’ 18.9’ 40.2’
150’ 23.6’ 50.2’
300’ 47.2’ 100.4’