Simrad SP90

Simrad SP90There is a selection between three different pulse lengths: Short,Normal and Long. In addition the pulse length will changeautomatically in accordance with the selected range. The tableshows 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 ofdetection as noise and reverberation are reduced.There is a selection between these different FM modes:• FM AUTO - This selection will automatically choose theoptimal number of frequencies for the selected range.- Ranges from 150 up to and including 900 meters will useFM4 (four frequencies).- Ranges from 1200 up to and including 8000 meters will useFM8 (eight frequencies).- In order to prevent different presentations caused bydifferent numbers of frequencies while changing rangebetween 900 and 1200 meters, the FM AUTO modeincludes a built-in memory function where Gain, Frequency,TVG, AGC, RCG, and PP-filter can be selected differentlyfor the FM4 and FM8 ranges. These selections will bememorized, and when you change between the 900 and 1200meters ranges, the system will reactivate the parameterselection you made the previous time the system wasoperating in that range interval.• FM1 - Transmits one-frequency pulse with a total pulse lengthof 1 ms.• FM2 - Transmits two-frequency pulses with a total pulse lengthof 4 ms.• FM4 -Transmits four-frequency pulses with a total pulse lengthof 16 ms.• FM8 - Transmits eight-frequency pulses with a total pulselength of 64 ms in ranges from 1200 and above, andfour-frequency pulses (FM4, 16 ms) from 900 meter and below.The selected number of frequencies are transmitted in one ping,and the receiver undertakes a spectrum analysis to compare thereceived echoes with the transmitter’s frequency code. Thisprovides a filtering effect, where only “own echoes” are displayed,and noise and other echoes are reduced. The table on the previouspage shows the maximum FM mode for all ranges.116 850-164511 / B