GP1670F_1870F Operator's Manual - Furuno USA

7. FISH FINDER OPERATIONS7.10 How to Measure Depth, Time Between LocationsYou can measure the depth to an object with the VRM. Also, you can measure the timefrom the right edge to a location. For example, you can measure how many minutesago the echo appeared.To measure the depth, press the up and down arrow pads on the CursorPad to putthe VRM on the object to measure the depth. To measure time, press the right and leftarrow pads on the CursorPad.The VRM cannot be operated when the Gain adjustment window is active.00’07”14.210Time elapsedVRM depth20307.11 How to Balance Echo StrengthA school of fish at a depth deeper than a school of equal strength in shallow waterappearsin weaker colors. This condition is caused by the attenuation of the ultrasonicwave. To display the schools of fish in the same colors, use the TVG. The TVG automaticallyadjusts the gain with depth so that echoes of the same strength and differentdepths are shown in the same colors.Unwanted echoesfrom surface0 ftUnwanted echoesare erased.0 ft300 ft 300 ftEchoes of the same sizeare displayed in differentsizes and colorsdepending on depth.Echoes of the same sizeare displayed in samesizes and colors.Do the following to balance echo strength:1. Open the [FISH FINDER] menu then select [FISH FINDER SETUP].2. Select [50 kHz TVG] or [200 kHz TVG].3. Enter TVG value. Lower the TVG setting to decrease the gain for near distance.7-13