Marport M4 Service Manual page 86

3. From the top right corner of the screen, click Spectrum.
4. From the top left corner of the screen, click Start Spectrum.
5. Select the hydrophone you want to test. Only the hydrophones that are switched on are
displayed. Select refresh to update the list.
6. To check the maximum, mean and real measures of noise level at a specific frequency, select
Marker on the left side of the screen.
7. Click the plot at the bottom of the screen to display the marker, made of two crossing red lines.
Move your mouse over the plot to place the marker on a frequency.
The noise levels are displayed under the part Marker. Use the marker to see at which
frequencies sensors are transmitting and at which frequencies the signal noise is higher. Look at
the Max and Mean measures of the noise level.
The acceptable average level of noise depends on the conditions (distance from the sensor to
the hydrophone, fishing method, type of hydrophone). You can have better performance with
the following levels:
• Active wideband hydrophone with high/low gain: below -100 dBV
• Active narrowband: NC-1-04 below -80 dBV / NC-1-07 below -100 dBv
• Passive hydrophone: below -110 dBV
8. Click Reset Max to reset the maximum value.
9. Check that there is more than 12dBV between the maximum noise level (dark blue line) and the
average noise level (light blue line) on the peak of the sensor frequency.
M4 System - 2 Mac Minis | V2 | Servicing and Maintenance
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