Chapter 6: Using the Fishfinder 139TVG (Time Varied Gain)The TVG (Time Variable Gain) reduces the clutter by varying the gain throughout thewater column. This function is useful for reducing the appearance of ‘noise’. Increasingthe TVG value increases the maximum depth to which TVG is applied. Decreasing itreduces the maximum depth. A low TVG value has little effect on gain in shallowwater; a high value decreases the gain in shallow water so that only the strongestechoes are displayed. TVG has no effect in Fishfinder Simulator Mode.Gain adjust (200/50)When the SELECTED FREQ is set to BOTH (seepage 137), the GAIN ADJUST soft key isenabled to allow you to select the frequency that the gain controls affect.To adjust this gain setting:Note:Gain adjustment for individual frequencies is only available when the selectedfrequency is set to BOTH.Adjusting the power settingThe Power control provides adjustment of the transducer signal.AutoThis is the default setting. When it is selected the DSM automatically determines therequired power setting based on the current depth, speed, and (bottom) signalstrength.ManualIf you wish to manually adjust the power to suit current conditions, you can adjust thepower level between 0 and 100%, in 10% increments. Lower power levels arenormally used in depth ranges less than 8 ft. (2.4 m) and higher power levels aretypically selected for depths greater than 12 ft. (3.7 m).Note:When the power level setting is changed there is a short delay while the newsetting takes effect.FISHFINDERSETTINGS...D7359-2GAIN... TVG100TVGadjust settingPress to highlightsoft keyToggle to manual andMANAUTOFISHFINDERSETTINGS...D8457-1GAIN ADJUST200 50GAIN...Toggle to therequired frequency
