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Fishfinder Help


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Hey guys, just after a bit of help with my sounder. I've got a Garmin 250 (black+white) with dual frequency tranducer (50/200kHz). I've been using it in shallow water from about 1.5m to 5m, in rivers/creeks where I do most of my fishing. I also fish in deeper impoundments occasionally.

I've been using it with the frequency set to 'dual' (as opposed to 50 or 200kHz) so that it shoots out both 50 and 200kHz waves at the same time. This gives both wide angle and narrow angle readings apparently.

Well when it's on this dual setting or the 50kHz (wide angle) setting I always seem to get constant fish symbols popping up one after the other at the same depth, usually quite shallow, when I know there are no fish there. When I change the setting to 200kHz (narrow angle) they go away, but I don't want to leave the setting on 200kHz because that only gives a very narrow angle reading which isn't much help in shallow water.

Is the dual frequency setting the best one to use? And what causes these 'false fish' to keep showing, and what can I do to get rid of them? I've played around with the 'Gain' (sensitivity) setting and all that seems to do is increase or decrease the size of the fish symbol.

The other problem I have, and it may be related, is that I can't seem to get decent readings or screen dispays when I turn 'fish symbols' off and use raw data only. When I turn fish symbols off the screen goes all dark and shaded, with crap everywhere and a big thick black line at the top of the water down to about 1m depth. I have to turn the 'Gain' setting right down to about 5-10% to get rid of most of this dark shading, and then it doesn't seem to show the fish, or at least I don't know what's fish and what's structure.

I'd like to use raw data only because I realise it's probably more accurate, but I get nice clear displays with easy to read shading and structure when fish symbols are turned on, and I get this with the 'Gain' setting up around 25-50%.

Should I really turn fish symbols off and use raw data only if I want accurate fish readings? And if so how do I improve my screen display? Also, what sort of setting should the 'Gain' be on - is 5 or 10% too low for shallow water? Are there any other settings that I should be looking at such as scroll speed? Should I look at tilting the transducer? (it's pretty much level now)



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first of all i'd only use the 200khz frequency unless fishing deep water, it gives you a narrower cone but more detail. opposite for the 50khz.

second of all turn off the fish symbols and try to use your manual settings, what you've done with the gain/sensitivity is correct. turn it right up to 100% and start backing it off until you get some shading, scatter and the fish arches.

thirdly make sure to read your booklet to see how you can further tweak your settings, adjusting depth, how fast the screen scrolls through, etc.

fourthly check out this site: http://www.lowrance.com/Support/Tips-and-Tutorials/Sonar-Tutorial/

hope that helps



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your 50khz beam will always give you grief in shallow water, refer your instructions as per the use of what the 50 khz actually does, basiclly, for deep water.as it is not more powerful, rather the unit listens better for echo's if you can get your head around that, thats why your getting signals everywhere or nothing, in water that shallow, it won't matter what beam your using actually, so i'd stick with the 200. and as for settings, i'm forever playing and adjusting my sounder,but i get good readings, but i swear there are no fish there. :laugh: but it's good watching my bait dropping down in 100 mtrs of water :P

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As I fish mostly in fresh impounments or shallow creeks and estuarys I set my sounder on arches and sensitivity at 80% and put it in auto and I never touch it after that, it stays that way all the time. One trick if you use fish ID in impoundments where there are yellas, if you see a large symbol with a smaller symbol beside it then in most cases its a big female yella with its husband. Another bit of useless info, if you pull up a large female yella, always have a quick look behind it as some times the husband follows her up.

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