Configuring the Uplink, Up and Down Settings

You can configure different settings for uplink, down and up soundings.

Before you begin

The sensor is connected to Mosa2.

About this task

Remember: Always click Apply after you change a setting and make sure there is a green check mark .


Click the tab Trawl Explorer.

Up/Down Soundings


  1. From NBTE Setup Options, select the sounding mode (see Sounding Modes for more information).
    Important: Down 1 + Down 2 sounding mode: configure Down 1 sounding in Down settings and Down 2 sounding in Up settings (Up Sounding Range, Ping Up Length, Ping Up Frequency, Up channel minimum TS, Up TVG Mode, TVG Up).
  2. From Down Sounding Range and, if applicable, Up Sounding Range, select the range according to how many meters you want to see under the sensor.
    Note: Range influences the display of echogram images. The smaller the range, the shorter the listening time and the better the quality of images. But if you set a bigger range, data arrives slower which results in poorer image quality. If you are using Down 1 + Up or Down 1 + Down 2 sounding mode, the image quality is even lower, as explained in Sounding Modes.
    Note: The range of the down sounding can automatically change to 20 meters if the distance to the bottom becomes lower than 20 meters and if you entered a trawl opening lower than 20 m. See next step to activate or not this feature.
    Important: This parameter must be the same in the sensor settings in Scala2.
  3. If you want the range of the down sounding to automatically change to 20 m when the bottom is closer (< 20 m):
    • Make sure you only use Down 1 sounding mode.
    • Enter the height of the trawl opening. It must be lower than 18.5 m. This is to make sure the sensor will search for the bottom beginning from this distance. This way, the sensor will not confuse the footrope with the bottom of the sea. For example, if the footrope is at 4 meters, enter a greater distance, such as 5 meters.
    Note: With the autorange feature, the echogram displays better quality images when the distance to the bottom is smaller.
    Important: Do not use the autorange feature if using Down 1 + Up or Down 1 + Down 2 sounding mode: you will have wrong data on the echogram.
  4. If you do not want the range of the down sounding to automatically change, enter 20 m or more.
  5. From Ping Down Length and, if applicable, Ping Up Length, enter a pulse length. Choose a pulse length according to the distance at which you need to detect fish. (the longer the pulse, the further you can see, but with a lower resolution):
    • Detection between 20 cm and 2 m: enter 0.1 ms
    • Detection between 50 cm and 160 m (V2: up to 80 m): enter 0.4 ms .
    Note: The maximum detection depth depends on ping frequency and type of bottom. The lower the ping frequency is, the longer the detection depth is.
  6. From Ping Up/Down Frequency, enter frequencies for down and, if applicable, up soundings. You can choose the same frequency for both because they do not transmit at the same time.
    Important: Frequency needs to be between 120-210 kHz.
    Important: Do not change ping frequency on a V3 sensor or it will have to be returned to a Marport sales' office for target strength calibration.

Target Strength


  1. For V3 version of sensors, Down channel minimum TS and Up channel minimum TS helps you detecting targets on the echogram. You can put -79 dB if you want to detect small targets. Otherwise, leave the default settings at -73 dB.
    Important: This parameter must be the same in the sensor settings in Scala2.
  2. Select the appropriate TVG (Time Variable Gain) mode. See About Time Variable Gain for more information.
    For V3 version of sensors, go to Down TVG Mode and, if applicable, Up TVG Mode:
    • 20 log: focus on bottom or school of fish.
    • 40 log: focus on individual targets.
    • 30 log: compromise between the two above settings.
    For V2 versions of sensors, go to TVG Down and, if applicable, TVG Up:
    • 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.