Vexilar FL-22 User Manual download pdf (Page 41)

Dead Zone

Beam angle has a large effect on the

performance of your asher. 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 would

have better results

with the 9°. This

is because of

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.

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

asher, or the optional S-Cable (page 42), 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

de p t h 8° 9° 12° 19° 20°

10’ 1.4’ 1.6’ 2.2’ 3.4’ 3.5

20’ 2.8’ 3.2’ 4.3’ 6.7’ 6.9

30’ 4.2’ 4.7’ 6.3’ 10.0’ 10.6

40’ 5.6’ 6.3’ 8.4’ 13.4’ 14.1

50’ 7’ 7.9’ 10.6’ 16.7’ 17. 6

60’ 8.4’ 9.4’ 12.6’ 20.8’ 21.2

70’ 9.4’ 11.0’ 14.7’ 23.4’ 24.7

80’ 11.2’ 12.6’ 16.8’ 26.8’ 28.2

90’ 12.6’ 14.2’ 20.0’ 30.1’ 31.7

100’ 14’ 15.7’ 21.0’ 33.5’ 35.3

120’ 16.8’ 18.9’ 25.2’ 40.2’ 42.3

150’ 21’ 23.6’ 31.5 50.2’ 52.9

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Vexilar FL-22 User Manual Page 41

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