Installation manual

Simrad SH80
About CW (Continuous Wave)
The frequency of the transmitter pulse is here constant, equal to
the selected frequency (if the optional multiple frequencies are
installed).
You can select between three different pulse lengths; short,
normal and long. In addition, the pulse length will also change
automatically in accordance with the selected range. The table
above shows the different pulse lengths given in milliseconds
(ms).
About FM (Frequency Modulation)
In the FM mode, the transmitter pulse is frequency modulated.
This provides a stable echo presentation and greater ability of
detection as noise and reverberation are reduced. You can choose
between the following FM modes:
•
FM Short: Transmits one-frequency pulse with a total pulse
length of 3.2 ms for all ranges.
•
FM Normal: Transmits one-frequency pulses with a total
pulse length of 6.4 ms up to the ranges of 150 meters, and
two-frequency pulses with a total pulse length of 12.8 ms for
the longer ranges.
•
FM Long: Transmits four-frequency pulses with a total pulse
lengthof16ms.
The selected number of frequencies are transmitted in one ping,
and the receiver undertakes a spectrum analysis to compare
the received echoes with the transmitter’s frequency code.
This provides a filtering effect, w here only “own echoes” are
displayed, and noise and other echoes are reduced. The table on
the previous page shows the maximum FM m ode for all ranges.
About PSK (Phase Shift K eying)
In the PSK mode, the transmitter pulse changes phase several
times during the 10,4 milliseconds transmission pulse. This
phase shift provides a high resolution presentation with retention
of the energy of the total pulse length. The frequency of the
pulse is constant, and equal to the selected frequency (if optional
multiple frequencies are installed).
Auto mode
In Auto mode, the transmitter pulse is made with a combination of
FM and CW to give an optimal echo presentation for all ranges.
This combination is designed from operational experience, and
will change automatically between FM Long in the shorter
ranges, and CW Long in the longer ranges. The table above
shows the mode and pulse lengths (ms) which are used for the
different ranges.
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164385/E