Doc. P/N:
WSP-009-008
Version: V1.3
Issue Date: April 2014
Operator Manual
Frequently Asked Questions (FAQs)
63
9.10 What is this constant signal on the sonar/fish finder display?
There are many sources of noise, interference and general acoustic reflections which can make these
displays difficult to use. A description of the different types of noise and ways in which you might be
able to determine and eliminate them follows.
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Sonar/Sounder
Other sound-producing devices will produce constant blips on the WASSP sonar display which will vary in
intensity and size depending on the transmission power and angle of the system. If you wish to continue
using your other sounders you can suppress this noise using the
Interference Filter
option.
►
Aeration
Air in the water around the transducer can cause transmitted signals to be absorbed or reflected premature-
ly resulting in false signal reports from the transducer.
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Biomass
Large bodies of photo plankton can float through the sea covering very large areas. This may be the source
of large areas of constant faint signal return through a region of the water column.
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Own Transmission
WASSP shows all received signals starting from half way through the transmission pulse. Thus you should
see a red or yellow ring at the top of the Sonar display. As power level and pulse width increase this signal
return will be stronger and larger.
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Keel Reflection
If the WASSP system is mounted in such a way that transmitted signals can reflect off the ship’s hull you may
find that there is a constant strong return shown on the sonar display. This may happen even if the hull is
just outside the 120degree transmission swath. If a strong signal follows the boat and is within the dimen-
sions of the ship then this signal is probably a reflection off your own ship. This will make it hard to detect
fish at this depth but otherwise shouldn’t affect the performance of your WASSP system.
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Electrical
There are an almost infinite number of ways in which Electrical Noise can influence system performance.
The first priority is that the system be well grounded – this means a large and preferably short grounding
wire connects the BTxR to the Power supply ground. WASSP is relatively protected by noise on Power sup-
ply sources but a very noisy supply could cause trouble. More likely causes of electrical interference are if
noisy, high power machinery or wiring is run beside the transducer cable. Electrical noise is either constant,
regular or transmit power dependant.
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Water Temperature Layers
A thin faint horizontal line that is present ping after ping in the same place could be a temperature layer. The
sea is often layered with various temperature layers due to pressure and surface mixing. Often a reflection
can be created at the depth where a significant change in water temperature occurs – causing an acoustic
return.
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Prop Noise
If the turbulent water flow off the props is directed onto the transducer face this could create aeration
noise. Especially relevant for lower frequency models – it may be possible to pick up the prop noise as an
acoustic source. For this reason it pays to mount the transducer some distance from the ships props. Prop
acoustic noise will appear on the side of the Sonar display close to the prop and will look like a regular pulse
or solid signal depending on the rotation speed.
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Vibration
Shudders of vibration and vibrating mounting structures can induce significant noise. Additionally a vibration
in mounting can cause motion compensation of the system to fail. Sharp jolts and vibrations will generate
rings of high signal.
