419050/B
81
Electrical self noise
Electrical or electronic self noise is picked up or generated in any other part of the
equipment than the transducer.
Hum picked up by the transducer cables or picked up from the power supply is usually
the most common source of electrical self noise. At higher frequencies – where rather
wide bandwidths are necessary – the noise from components, transistors or other
analogue electronic may be a limiting factor.
Reverberation
When you transmit an acoustic pulse into the water to search for a target, echoes will also
be returned from any other objects in the beam, and some times even from the seabed.
The energy reflected from these "unwanted" objects is referred to as
reverberation
.
Reverberation is generated when the echoes from your SC90 transmission are reflected
not only by fish and valid targets in the water, but also from the seabed and from the sea
surface. Reverberation is often regarded as noise. There are two kinds of reverberation:
•
Volume reverberation
: This is caused by minute plankton and air-bubbles in the water.
This reverberation often has daily cycles in intensity.
•
Surface and bottom reverberation:
The surface reverberation is dependent on the
weather condition, while the bottom reverberation depends on the roughness of the
bottom.
Reverberation is often a limiting factor, especially if you are searching for smaller
targets. The echoes from the bottom will depend on the bottom properties; how uneven it
is and what kind of bottom you have under your vessel (rock, mud, sand). Your current
tilt setting will also have an effect on the reverberation. The echo from the sea surface
will vary with the current sea state and your current tilt setting.
The illustration demonstrates how the bottom and the sea surface return echoes back
to your SC90.
A
In this situation you will be able to identify the upper school of fish, but the lower
school will be hidden in the shadow of the seabed rock formation.
B
In this situation you will see several weak echoes from the waves and from the rock
on the bottom, but you will still be able to identify the school of fish.
Summary of Contents for SC90
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Page 16: ...14 419050 B Simrad SC90 ...
Page 219: ...419050 B 217 Øverland UPC 3005 Dimensions Cable layout and interconnections ...
Page 223: ...419050 B 221 Øverland UPC 5000P Dimensions Cable layout and interconnections ...
Page 438: ...436 419050 B 427177 Transducer dock dimensions page 494 Simrad SC90 Installation Manual ...
Page 441: ...419050 B 439 Drawing file ...
Page 442: ...440 419050 B Simrad SC90 Installation Manual ...
Page 445: ...419050 B 443 Drawing file ...
Page 452: ...450 419050 B Simrad SC90 Installation Manual ...
Page 455: ...419050 B 453 Drawing file ...
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Page 463: ...419050 B 461 Drawing file ...
Page 468: ...466 419050 B Simrad SC90 Installation Manual ...
Page 469: ...419050 B 467 Related topics Installing the optional gate valve DN350 page 84 Drawing file ...
Page 471: ...419050 B 469 Drawing file ...
Page 473: ...419050 B 471 214043 Gate valve installation DN350 Drawing file ...
Page 475: ...419050 B 473 422915 Gate valve installation DN350 Drawing file ...
Page 477: ...419050 B 475 083045 Gate valve installation DN500 Drawing file ...
Page 479: ...419050 B 477 33414 Gate valve dimensions DN350 Drawing file ...
Page 480: ...478 419050 B Simrad SC90 Installation Manual ...
Page 481: ...419050 B 479 Related topics Installing the optional gate valve DN350 page 84 Drawing file ...
Page 482: ...480 419050 B 33473 Gate valve dimensions DN350 Simrad SC90 Installation Manual ...
Page 483: ...419050 B 481 Related topics Installing the optional gate valve DN350 page 84 Drawing file ...
Page 484: ...482 419050 B 33498 Gate valve dimensions DN500 Simrad SC90 Installation Manual ...
Page 485: ...419050 B 483 Drawing file ...
Page 487: ...419050 B 485 37357 Gate valve dimensions DN500 Drawing file ...
Page 488: ...486 419050 B Simrad SC90 Installation Manual ...
Page 489: ...419050 B 487 Related topics Installing the optional gate valve DN500 page 103 Drawing file ...
Page 491: ...419050 B 489 Drawing file ...
Page 494: ...492 419050 B Simrad SC90 Installation Manual ...
Page 495: ...419050 B 493 Related topics Installing the optional gate valve DN350 page 84 Drawing file ...
Page 497: ...419050 B 495 Drawing file ...
Page 542: ... 2018Kongsberg Maritime ISBN xxx ...
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Page 544: ...Simrad SC90 Fish finding sonar Installation Manual ...