User manual FURUNO CH-28 OPERATORS MANUAL

[. . . ] A heater can melt the equipment's power cord, which can cause fire or electrical shock. The fuse in the hull and transceiver units protect them from overvoltage, equipment fault and reverse polarity of the ship's mains. Wait until the transducer switch [] lights steadily and then turn off the power. WARNING Keep heater away from equipment. i CAUTION Do not exceed 20 knots when operating the equipment and do not exceed 15 knots when lowering or raising the transducer. Use of the equipment as a stepping stool, for example, may result in personal injury or damage to the equipment. [. . . ] By observing the bottom condition on the display, the skipper can prevent net damage. (A) Flat bottom Tilt angle: 10° to 15° Decreased tilt angle Only half of vertical beam width captures the bottom. (B) Flat bottom Tilt angle: 20° or more (C) Sloping bottom Tilt angle: 20° or more Bottom is displayed narrower and in stronger colors when compared to (A). Shallow bottom is displayed in a strong color and with a short tail. Bottom The deeper, sloping bottom echo is displayed in a weak color and with a long tail. Figure 2-21 Bottom echoes 2-24 Fish schools A fish school appears as a mass of echoes on the screen. The color of the mass shows the density of fish schools on the sonar beam. To find distribution and center point of a fish school, try several different tilt angles. (A) Sea surface fish Tilt angle: 0° to 10° Fish school Bottom echo not displayed because of decreased tilt angle. Sea surface reflections are present. Sea surface reflections (B) Midwater, bottom fish Tilt angle: 30° or more Fish echo which appears before bottom can be detected. Bottom Fish school Large midwater fish school is present. Tilt angle: 0° to 20° Fish echo which appears together with or after bottom can be detected. Fish school Bottom When the tilt angle is shallow, the reflection echo from bottom is weak and the fish echo which appears from bottom is easy to find. Figure 2-22 Fish schools 2-25 Sea surface reflections To reduce sea surface reflections, set the tilt angle to 5° or higher, so the upper edge of the sonar beam does not hit the sea surface, or adjust TVG. When a decreased tilt angle is used, sea surface reflections cover a large area as illustrated below. Sea surface Tilt angle indication 17° Sea surface reflections Sea surface 17° Figure 2-23 Sea surface reflections Wake A wake produced by own ship or another ship can be a strong reflecting object when a decreased tilt angle is used. As the wake appears as a thick continuous line, it can be easily distinguishes from a fish school. A wake contains many air bubbles which attenuate ultrasonic energy, making it difficult to sound beyond the wake. Other ship Own ship Own ship's screw noise Wake produced by other ship Own ship's screw noise Own ship's wake (produced when own ship turned) Figure 2-24 Wake 2-26 Sidelobe echo (false echo) An ultrasonic wave is emitted only in the direction set by the [TILT] control, however there are some emissions outside the main beam. The energy of the sidelobe is fairly weak but when the water is comparatively shallow and the bottom is rocky and hard, strong signals are detected by the sidelobe. These are represented on the display as a false echo as shown below. Mainlobe echo Sidelobe Sidelobe echo Mainlobe The bottom echo detected by sidelobe appears at a certain tilt angle when the sidelobe points vertically. Also, poor soundome projection may result in a similar false echo. Figure 2-25 Sidelobe echoes Noise and interference When the fishing ground is crowded with many fishing boats, the sonar is subject to interference from ultrasonic equipment (echo sounder or sonar) on other boats as well as those on own ship. For instance, interference from the sonar operated on other boats will show itself on the display as in (A) in the figure below. ON Target lock indicator Transducer status indicator Position in latitude*, longitude* Course*, speed* Number of lines increases by one with each train. 213' W CSE 357° SPD 9. 9 kt PORT STBD Cursor -90° 0° Heading +90° Horizontal Display (main display) Strata Display (sub window) Figure 2-29 Horizontal/strata display The horizontal display appears in the main window; the strata display in the sub window. This is useful in bottom trawling to avoid projections which may damage the net. Coverage for the horizontal mode is 360° picture, and for the strata display it is maximum 90 from port to 90° starboard. The strata display may be adjusted with the [RANGE] and [SECTOR] controls. The message MAIN WINDOW CONTROLLABLE or SUB WINDOW CONTROLLABLE appears with each pressing of the key. A red cursor appears in the sub window when it can be controlled. 2-30 Color bar for the strata display The depth of the bottom each in all directions is displayed in the sub window, in the colors set by the color bar for the strata display. The color bar for the strata display shows search angle range below 336 degrees. Strongest color Weakest color -90° -18° -12° -6° 0° 6° 12° 18° 90° Color bar for strata display The undulation of the bottom echo in all directions is shown by the colors on the color bar for the strata display. The position of the weakest echo can be changed with the [RANGE] control, and the width of each color on the color bar for the strata display with the [SECTOR] control. Use the [SECTOR] control to adjust width of each color. Weakest color Use the [RANGE] control to move the location of the weakest echo color. Note: TILT, TRAIN, FULL/HALF, FAST SCAN, R/B, EVENT, TARGET, CUSTOM MODE controls may only be operated from the main window. When you attempt to operate them from the sub window the message "SELECT MAIN WINDOW. " appears for about four seconds. Flat bottom and strata display Each layer on the strata display is equal to one train on the horizontal display. -90° PORT STBD +90° Color "a" on the color bar Color "a" When the bottom is flat the horizontal display inscribes the bottom as a true circle, and the strata display inscribes the color of point "a". The color of this position on the color bar is the color of point "a" on the strata display. Figure 2-30 Flat bottom and strata display 2-31 Projection in fore direction and strata display Color "b" on the color bar is displayed here. [. . . ] The TX FREQUENCY of the transducer is measured and displayed. · 6-6 · · · TRAIN shows a figure between 355-359 if normal. TEST COUNT shows the number of times the test has been consecutively executed. At the bottom of the screen there are two major groups of zeroes (0), and they represent the keys and controls on the control panel and remote controller. Press a key and its on-screen location shows "1" while the key is pressed and "0" when it is released. [. . . ]