Kongsberg Simrad SP90 Series, Руководство пользователя

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Basic theory
AGC
AGC means “Automatic Gain Control”. If you wish the SP90
sonar to control its own gain automatically, you must enable this
function. You can choose from three different levels. When
the AGC has been switched on, the manual
Gain
setting you
have chosen will only work on shorter ranges. Once the range
is increased, the computer will gradually take control over the
sonar gain.
Default setting on the SP90 sonar is
Medium
.
PP Filter
PP Filter means “Ping-to-Ping Filter”. When this function is
activated, the sonar will compare the echoes from one ping with
the echoes from the next pings. If an echo is present at the first
ping, but then disappears at the next, the sonar will interpret this
as noise and reverberation, and remove it.
If you choose setting
Weak
, the sonar will only compare two
consecutive pings. If you choose settings
Medium
or
Strong
the
sonar will compare four and eight pings respectively.
Default setting on the SP90 sonar is
Medium
.
Pulse form and length
On the SP90 sonar, you can transmit sound modulated as FM
or CW.
FM means “frequency modulated”, which means that the
frequency of the transmitted pulse is changed during the
transmission. In most cases this method will provide better echo
presentation and stability, and you will avoid excessive noise
and reverberation.
Default setting on the SP90 sonar is
FM Auto
. In this transmission
mode, the sonar will automatically choose from a set of different
frequencies depending on the current range.
CW means “continuous wave”, which means that the
transmission frequency is fixed during the entire pulse. When
you use CW transmission you can choose the length of the
pulses. In a search phase under good conditions, you should try
setting
Long
. If the conditions worsen, try to shorten the pulse
length. This will make it easier to distinguish the various echoes,
and the reverberation will be reduced.
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