Trawl Explorer | V5 | Sensor Configuration
• 40 log: focus on individual targets.
• 30 log: compromise between the two above settings.
For V1 and V2 versions of sensors:
• In
TVG Coefficient
, enter between 0.500 and 0.520 to have approximately the equivalent of
20 log , 0.75 for 30 log or 1 for 40 log.
• In
Attenuator Coefficient
, enter 25.
• Leave
VCO Coefficient
default settings at 3.
About Time Variable Gain
TVG (Time Variable Gain) is a method that compensate signal loss in the water. Basically, the aim is
to have targets or sea bottom displayed in the same color on the echogram, whatever the distance
from the sensor.
When the sounder sends pings, the deeper the target is, the more attenuated signals will be
received and sent back. As a result, if the signal is too much attenuated, echoes (target strength)
received from a target might not be as strong as they should be. TVG is here to compensate this
effect. It uses a lower gain level when signals travel toward a target at a small distance and higher
gain level when signals travel toward deeper targets. The end result is to compensate sounding
attenuation and therefore to show a same target strength for a same target at different depths.
You can choose between three different TVG modes:
• 20 log: use to focus on the bottom, footrope or a school of fish.
• 40 log: use to focus on individual targets.
• 30 log: compromise between the two others.
For example, if you want a good view of the footrope, select a TVG mode at 20 or 30 log. You can
see on the images below that the footrope is clearer at 20 and 30 log.
If you want a good view of individual targets, you can see that with 40 log, targets in the water
column are clearer.
20 log
30 log
40 log
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