CA42/50/52 Glossary of terms Appendix A
155
where black is especially useful during nighttime operation when the white back-
ground could appear too bright.
Echosounder frequency – 38 kHz, 50 kHz or 200 kHz can be selected to suit the
task. 200 kHz is for general purpose and offers optimum discrimination and a
narrow transmitter beam. 38 kHz and 50 kHz are for searching in a wider area,
determining bottom conditions and going the deepest.
Event marker – allows the user to set a vertical marker on the screen at the
current ping to indicate a school of fish, etc.
Expansion (zoom) – this function allows you to take a closer look at a particular
section of the water underneath your boat. You can expand the view near the bot-
tom (Bottom expansion) or near the Variable Range Marker (VRM expansion).
The amount of expansion can be adjusted in “Expansion window”, Presentation
setup.
Gain – is another way o saying “sensitivity”, or possibly “volume”. Increasing
the gain setting of the CAXX will allow you to see smaller and deeper targets.
If the gain is set too high, however, you will begin to see “noise” and unwanted
targets. Generally speaking, you want to set the gain control just below the point
that you begin to see speckles of “noise” between surface and the bottom on the
screen.
Ping to ping filter – can be set to either on or off. With the filter “off”,theneach
received echo will be reflected on the screen. Whereas with the filter “ON”,the
system will compare every two echoes received and only reflect on the screen
what is received from both echoes, which will give a more uncluttered and
precise recording.
Pulse length – the transmitted pulse length can be set to OFF for observing noise
in the water (Auto range will switch to manual mode). Set to AUTO, the
optimum setting will be applied according to the water depth. Or it can be set
manually, if a specific pulse length is required:
SHORT less than 10m deep water
MEDIUM between 10 and 50 m deep water
LONG more than 50m deep water
) A long pulse will reach deeper but give less resolution.
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