Simrad FS70 -, Operator'S Manual

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Theory of Operation
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Maximize Range - The pulse length calculation can be optimized to increase the detection
range of the sonar head. Generally, the longer the pulse length, the more energy is
transmitted into the water which could then travel a longer distance and get reflected from
the targets that are further away from the sonar head. It has been determined that the pulse
length corresponding to 80% of the sample period can increase the detection distance of the
targets without a major drain on the sonar head power supply.
The pulse length increases linearly with increasing operating range. The system will
automatically set the pulse length to match the range, unless manually adjusted by the
operator.
2.5.5 Peak Detection
Depending on the operational settings, the combination of small target size, short pulse
length and long sample period could result in the acoustic return from the target falling
between two samples and therefore not beings seen on the sonar image.
To remedy this, it was decided to take additional samples in the interval between two
displayed samples and select the strongest echo target during that interval for the sonar
image display. This is generally referred to as Peak Detection because we are detecting the
peak value of signal in between two samples. The user can enable the Peak Detection and
select the number of additional samples that the system takes in order to detect the peak
value in order to optimize the detail in the image while maintaining an acceptable signal to
noise ratio.