Controlling The Gain And Range Settings; Adjusting The Gain (Echo Sensitivity) - Simrad SN90 Operator's Manual

Operating procedures

Controlling the gain and range settings

Topics
Adjusting the gain (echo sensitivity), page 63
Adjusting the TVG (Time Variable Gain) setting, page 65
Adjusting the sonar range, page 65
Adjusting the intensity of the echo presentations, page 67
Changing the tilt, page 67
Adjusting the bearing, page 69

Adjusting the gain (echo sensitivity)

Some echoes are weak while others are stronger. To compensate for this it is often
necessary to adjust the sensitivity of the SN90. This adjustment is commonly referred
to as gain.
Context
You can compare this gain setting with the volume control on your car radio. When
the gain is increased, the echoes will appear stronger. Weak echoes will be easier to
see. However, since you also increase the acoustic noise in the reception, the SN90
presentations will also show this noise. Too much gain may therefore "distort" the
presentation.
Comparing the gain function with the volume control on your car radio is not very
accurate. In fact, the gain in the SN90 is constant. The function is used to adjust
Gain
the sensitivity. This done by controlling the minimum level of detection. When you
increase the gain level (more positive number) , you reduce the minimum level, and thus
increase the sensitivity.
The echo strength (A) changes with time. The minimum level of detection (B) is adjusted
up or down with the function. Increasing the with a more positive number
Gain Gain
63
381295/B