Observation Range Versus Operational Frequency - Simrad ES80 Reference Manual

Observation range versus operational
frequency
Absorption increases dramatically with frequency in salt water. For maximum
observation range you should select a low operating frequency, a large transducer and the
maximum transmit power.
The key facts related to observation range versus operational frequncy are:
• Observation range increases when the operational frequency is reduced.
• Resolution increases when the operational frequency is increased.
If you wish to work in deep waters, you need a low operational frequency.
If you wish to work with high resolution, you need a high operational frequency. The
observation range is then limited.
Using the Simrad ES38B transducer (38 kHz, 7x7 degrees, 2000 W) you can observe
a 60 centimeter cod down to 950 meters, while bottom detection works down to 2800
meters. However, with the Simrad ES200-7C transducer (200 kHz, 7x7 degrees, 1000
W) you can only observe that same cod down to 270 meters. Bottom detection becomes
unreliable below 500 meters.
Typical observation ranges are shown in the table.
Maximum detection depth (Split-beam transducers)
Trans- Fre-
ducers quency
(kHz)
ES18-11 18
ES38B 38
ES70-11 70
ES120-7C 120
ES200-7C 200
Maximum detection depth (Single-beam transducers)
Trans- Fre-
ducers quency
(kHz)
38-7 38
38-9 38
38/200D 38
50/200D 50
50-18 50
50-7 50
406273/C
Pulse Band-
duration width
(ms) (hz)
8,21 382
4,09 766
2,05 1526
1,02 3026
1,02 3088
Pulse Beam
duration angle
(ms) (deg)
4 7
4 9
4 13x21
2 10x16
2 18
2 7
Concept descriptions
TX Range
Power fish
(W) (m)
2000 1100
2000 950
800 450
1000 440
1000 270
Band- TX
width Power
(Hz) (W)
766 2000
766 1500
766 1000
1493 1000
1526 500
1493 2000
Range
bottom
(m)
7000
2800
1100
850
550
Range
(m)
3000
2600
2100
1400
1400
1900
457