Installation manual

Simrad SP70
134
850-164186 / Rev.D
There is a selection between three different pulse lengths:
Short, Normal and Long. In addition the pulse length will
change automatically in accordance with the selected range. The
table shows the different pulse lengths given in milliseconds
(ms).
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.
There is a selection between these different FM modes:
 FM AUTO - This selection will automatically choose the
optimal number of frequencies for the selected range.
 FM1 - Transmits one-frequency pulse with a total pulse
length of 1 ms.
 FM2 - Transmits two-frequency pulses with a total pulse
length of 4 ms.
 FM4 - Transmits four-frequency pulses with a total pulse
lengthof16ms.
 FM8 - Transmits eight-frequency pulses with a total pulse
lengthof64ms.
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, where only “own echoes” are
displayed, and noise and other echoes are reduced. The table on
the previous page shows the maximum FM mode for all ranges.