About Transducers Cone Of Sound; Dead Zone; Output Power - VEXILAR FL Series Owner's Manual

A BO UT TRANSDU C ER S
Cone of Sound
The cone of sound is the area the sound waves cover as they are emitted from the
transducer. Generally, this area is thought of as three-dimensional cone, such as an
upside-down ice cream cone. In actuality, the cone of sound is not so precisely defined.
It is an irregular shape with edges that taper rather than end abruptly. Additionally, the
cone of sound will vary slightly from transducer to transducer.
Transducer
Theoretical Cone Angle
The theoretical cone
angle is what the
transducer's specification
defines. This is the area
where the intensity of the
sounds waves drop to a
specific point (-6dB).
Most objects are visible inside the theoretical cone, but you can also see objects outside
the theoretical angle yet within the side and main lobes. These objects must be large
enough to sufficiently reflect the sonar signal. Some of these objects can be things like the
face of a sharp dropping bottom, a large rock, or even a good size fish or tight group of
smaller fish.
52
Flasher-Family-Manual-2019.indd 52-53

Dead Zone

Beam angle has a large effect on the
performance of your flasher. There is more to
it than simply area of coverage. The correct
beam angle to use depends entirely on your
application. If you are fishing for suspended
fish then you would be pleased with the
performance of the 19° cone. However, if you
were going after fish that are holding right
on the bottom along a steep drop-off, you
Side Lobe
Not all of the sound
waves come out
of the transducer's
bottom. Some sound
comes out the sides
and even the top.
Main Lobe
The main lobe is
where most of the
sound waves go.
They extend out in
all directions, some
sides more than
others.

Output Power

Your depth finder puts out a constant amount of power, or sound energy. It does not
matter where you have the gain level set. Gain simply controls how much you amplify the
signal that is returned from below. 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 in shallow water. A narrow beam transducer
can be overpowering in shallow water. The use of the LP (Low Power) mode on your
flasher, or the optional S-Cable (page 58), will solve this problem.
Remember to NOT use LP mode or the S-Cable in depths beyond 20 feet. You will find
that you need to turn your gain control up much higher than normal. This will give a noisy
display and make interference from other units much more likely.
Cone angle vs
Diameter of Coverage
d 8° 9°
epth
10' 1.4' 1.6'
20' 2.8' 3.2'
30' 4.2' 4.7'
40' 5.6' 6.3'
50' 7' 7.9'
60' 8.4' 9.4'
70' 9.4' 11.0'
80' 11.2' 12.6'
90' 12.6' 14.2'
would have better
100' 14' 15.7'
results with the 9°.
120' 16.8' 18.9'
This is because of
150' 21' 23.6'
something called
dead zone. Dead zone is an area within the transducer's 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 fishing 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 holding on the bottom on
the low side of the slope 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.
12° 19° 20°
2.2' 3.4' 3.5
4.3' 6.7' 6.9
6.3' 10.0' 10.6
8.4' 13.4' 14.1
10.6' 16.7' 17.6
12.6' 20.8' 21.2
14.7' 23.4' 24.7
16.8' 26.8' 28.2
20.0' 30.1' 31.7
21.0' 33.5' 35.3
25.2' 40.2' 42.3
31.5 50.2' 52.9
53
5/15/19 12:27 PM