Echotrac MKIII Operator's Manual 4.06
Page 24 of 48
January 21, 2019
5.2.2.8
Min. Gate Width
The digitizer maintains a tracking gate that changes from ping to ping dependent on water depth and number of
pings inside the gate. This parameter is the minimum gate width that the digitizer sets once it has received a number
of good returns. The value entered is the percentage of water depth. Use a lower percentage for smooth bottoms
and use a larger percentage for rapidly changing bottom where the bottom might move outside the tracking gate.
5.2.2.9
Skip Alarms
This parameter buffers the most recent valid bottom detection and will continue outputting that value through the
serial port to the data acquisition software for the number of sounding cycles selected. When a value of 0 is
entered the Echotrac will output a zero if it does not detect a valid return. This parameter is useful when the
digitizer is having a difficult time detecting the bottom due to noise in the water column and the operator does not
want to edit the resulting spikes in the data acquisition software.
5.2.2.10 Sub-bottom TVG
This parameter is used in areas with a lot of silt where the low frequency is having trouble getting a signal return
from the hard bottom. The high frequency channel is used to determine the top of the silt layer, which is sent to
the low frequency board. The sub-bottom TVG parameter is then used to increase the gain to the low frequency
board in 1db/meter steps beginning where the silt bottom starts. This has the effect of compensating for the
increased loss of signal in the silt layer. Use the SB TVG Range parameter to limit the duration of the increased
TVG gain so the second return is not amplified as well.
Using this parameter depends of having the high frequency reliably tracking the top of the silt layer.
To use this parameter set the MKIII to transmit dual frequency. Set the gain for the high frequency to Auto. As an initial
step, set the Sub-bottom TVG to a value of 3. Set the gain knob for the low frequency channel so that the top of the silt
layer is not visible but the hard bottom is visible. Do not use the Auto gain for the low frequency channel. If the signal
from the hard bottom is the same amplitude or weaker than the hard bottom, increase the Sub-bottom TVG parameter.
If the signal from the hard bottom is very strong and the signal from the silt bottom is still visible lower the gain setting.
5.2.2.11 SB TVG Range
This parameter limits the duration of the Sub-bottom TVG parameter so that the second return is not amplified.
The value entered is in meters or feet depending on the units used.
5.2.2.12 Pre Amp Gain
This parameter controls the gain to an optional signal interface card in the Echotrac MKIII. This gain does not
affect the normal MKIII receiver.
5.2.2.13 Missed Returns
Sets the number of returns the digitizer must miss before it starts expanding the gate. A value of 1 will cause the
digitizer to react very quickly and 50 will cause the gate to react very slowly.
5.2.2.14 Mode
Only Echotrac CV2 and CV3 firmware 3.24 and higher support this feature. In regular Echotrac Mode, the
Echotrac CV will operate as a normal echo sounder. In Sub-bottom mode, the Echotrac CV will output a large Low
Frequency packet with 3200 samples, which is used for sub-bottom profiling. Some applications may not be set
up to receive this large data packet.
Summary of Contents for Echotrac MKIII
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