1.14 Adjusting the Sensitivity
The GAIN control adjusts the sensitivity of the receiver. It works in precisely the same manner as the volume control of a broadcast receiver, amplifying the signals received.
The proper setting is such that the back- ground noise is just visible on the screen. If you set up for too little sensitivity, weak ech- oes may be missed. On the other hand ex- cessive sensitivity yields too much background noise; strong targets may be missed because of the poor contrast between desired echoes and the background noise on the display.
To adjust receiver sensitivity, transmit on long range, and adjust the GAIN control so back- ground noise is just visible on the screen. The current gain setting is shown by the “GAIN bar” at the top
1.15 Suppressing Sea Clutter
If the control is set too low, targets will be hidden in the clutter, while if it is set too high, both sea clutter and targets will disappear from the display. In most cases adjust the control until clutter has disappeared to lee- ward, but a little is still visible windward.
1.Confirm that the sensitivity is properly adjusted, and then transmit on short range.
2.Adjust the A/C SEA control so small tar- gets are distinguishable but some clutter remains on the display.
A/C SEA control | A/C SEA control |
off | adjusted |
Figure 1-11 How to adjust
the A/C SEA control
Echoes from waves cover the central part of the display with random signals known as sea clutter. The higher the waves, and the higher the scanner above the water, the further the clutter will extend. When sea clutter masks the picture, suppress it by the A/C SEA con- trol, rotate for manual adjustment, push for automatic adjustment.
Manual adjustment by the A/C SEA control
The A/C SEA control reduces the amplifica- tion of echoes at short ranges (where clutter is the greatest) and progressively increases amplification as the range increases, so am- plification will be normal at those ranges where there is no sea clutter.
The proper setting of the A/C SEA control should be such that the clutter is broken up into small dots, and small targets become distinguishable.
Automatic adjustment by the A/C AUTO control
The A/C AUTO control automatically sup- presses sea clutter as well as rain clutter. Push the A/C SEA control to turn on the au- tomatic A/C circuit. A/C AUTO appears at the bottom left corner when the A/C AUTO cir- cuit is on. Fine adjustment of the circuit can be done with the A/C RAIN and A/C SEA con- trols.
CAUTION
Turn off the A/C AUTO feature when its use is not required; it can erase weak target echoes.