Simrad CE34 ChartSounder Manual page 58

Chapter 4-8 CE34/44/54 Echo menu
the display screen. Selecting Auto range will cause the CEXX to
change the basic range setting(s) to keep the displayed bottom in
the lower half of the display. For instance, as your boat moves into
deeper waters, the system will automatically switch to a deeper
range, always keeping the displayed bottom in the lower half of the
display. Manual range allows the operator to set the range displayed
on the screen.
Gain – is another way of saying "sensitivity", or possibly "volume".
Increasing the gain setting of the CEXX 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.
White line – is a control which places a white/black line at the
displayed sea floor and blanks out 4 pixels just below the line. The
purpose of this is to help the user detect targets, such as fish, which
are very close to the sea floor and whose echoes tend to merge with
those of the sea floor itself.
Expansion window (zoom level) – can be selected in eight steps,
ranging from 1 to 50 meters, or converted to feet or fathoms (refer
to Setup for units, section 8.4). 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 bottom (Bottom expansion) or
near the Variable Range Marker (VRM expansion).
TVG – Time Varying Gain – is a control that allows the CEXX to
make corrections for most of the losses and absorption that occurs as
sound energy passes through sea water. There are three settings to
choose from, Normal, Special and OFF.
The setting "Normal (20 log R) is for general fish finding at depths
down to 50m (150') and it will also give a uniform bottom echo pres-
entation at shallow, mid and deep water.
The setting "Special (40 log R) will adjust the TVG to show the same
echo strength for a given size fish at varying depths.
The OFF position is used for net sounders. In OFF position the TVG
is inactive which means that the sounder operates with a fixed gain
between each transmitter pulse. Auto range is switched to manual.
Ping to ping filter – can be set to either on or off. With the filter
"off", then each received echo will be reflected on the screen.
Whereas with the filter "ON", the system will compare every two