Stimmen - 3, Durchschnittliche Bewertung: 3.3
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Anleitung Zusammenfassung
In the latter case, bearing (“B”) is indicated as follows: B P ------- on the port side B S ------- on the starboard side 2-8 FINE TUNING THE PICTURE Eliminating Unwanted Feeble Echoes Echoes from targets such as seabed and fish return to the transducer in order of distance to them, and when we compare their intensities at the transducer face, those from nearer targets are generally stronger when their reflecting properties are nearly equal. The sonar operator will be quite inconvenienced if these echoes are directly displayed on the screen, since he can not judge the actual size of the target from the size of echoes displayed on the screen. To overcome this inconvenience, the TVG function is incorporated. It compensates for propagation loss of sound in water; amplification of echoes on short range is suppressed and gradually increased as range increases so that similar targets are displayed in the similar intensities irrespective of the ranges to them. The CSH-23F/24F has three TVG functions, NEAR, MEDIUM and FAR, and they mainly compensate for propagation loss on short, middle and long ranges respectively, centered at the ranges shown below. The higher the TVG setting the greater the amplification of echoes. About 100 m Near Far Med About 400 m Figure 3-1 Principle of TVG The TVG is also used to suppress unwanted echoes and noise which appear in a certain range area on the screen such as sea surface reflections and cruising noise. To set TVG properly, do the following: How to adjust TVG 1. Open sub panel 2. 2. Select TVG•TX. 3. Set TVG NEAR, MEDIUM and FAR to 5. (These are the standard settings and you can maintain them in most cases.) 4. When sea surface reflections or plankton layers disturb the picture, decrease appropriate TVG option by one or two steps by pressing – (minus) key. 5. When fish school is located on a long range setting (about 800 meters) which is approaching own ship. Adjust the tilt to keep the fish school in the center of the sonar beam, namely, fish school is displayed in strongest colors possible. Confirm that the fish echo is displayed in the same color as it approaches. If the color suddenly changes to weaker colors as the fish enters MEDIUM and NEAR areas, the TVG is improperly set. Adjust the TVG. If this again produces sea surface reflections and noise try to remove them with AGC and NL controls. Note: If the above procedure does not produce satisfactory results, the TVG curve can be changed on the SYSTEM menu. The 30 log setting is normal. The 25 log setting is useful for searching fish schools near shorelines or shallow waters. The 35 log or 40 log setting raises the gain on a long range and is suitable for searching tuna, bonito, etc., which are usually searched with high gain setting.Ask for FURUNO dealer for detail. Suppressing Seabed Tail AGC (data setting window: SIGNAL, SIGNAL PROCESS) The AGC functions to automatically reduce the receiver gain only against strong echoes such as the seabed or a large fish school. Since weak echoes remain unaffected, a small fish school becomes easier to detect. Adjust it so that the AGC works only on seabed reflections. Do not set it too high; weak echoes may be missed. Pulselength (data setting window: TVG•TX, PL) The pulselength control determines the length of the transmission pulse emitted into the water. While a longer pulse is advantageous for long range sounding, it has the disadvantage of being poor in discrimination of targets, that is, ability to separate several closely located targets. When searching bottom fish, therefore, it is useful to shorten the pulselength in order to separate fish echoes from seabed reflections. Decrease the PULSELENGTH setting to shorten the pulselength. For search of surface and midwater fish in which seabed reflections are not so strong, use the longest pulselength “9”. 2AGC (data setting window: SIGNAL, SIGNAL PROCESS) While it is ideal to suppress seabed echoes with the AGC control alone there are some fishing grounds where this is not possible. (The high power sonar has the advantage of long-range detection but this can also be a disadvantage, since weaker echoes may be hidden in strong, unwanted echoes such as the seabed.) If you cannot suppress seabed echoes or sea surface reflections by the AGC control alone, use the 2AGC control. Normally a setting of 2 or 3 is suitable. For especially strong echoes, use a setting of 4 or 5. AR, -4 to -1: Adjusts horizontal beamwidth. 2AGC function is fixed at “3”. 0: 2AGC function is off. 1 to 5: Larger the number, the greater the effect of 2AGC. Suppressing Seabed and Sea Surface Reflections in Shallow Waters Data setting window: TVG•TX, OUTPUT In shallow fishing grounds with hard or rocky bottom, seabed reflections often interfere with wanted fish echoes and they can not be eliminated sufficiently with the aforementioned TVG and AGC controls, especially when the TILT is set to a larger angle in order to track fish schools approaching within 400 m. In suc...