Traditional Fish Finder Depth Readings

[RuralMT]

Good afternoon all.  I recently purchased a Garmin Striker 4 DV for use on my canoe during the summer, but have had it out several times on the hardwater to great success.  However, last weekend, I opened up some recently used holes to spare myself from drilling through 16" of ice with my hand-auger.  I know beyond a doubt that I was over 60-70 fow, but my sonar was reading 12.5', and being a new owner, I wasn't sure how to fix it. 

I noticed the folks who fished that morning had chummed their hole with oatmeal, and I suspect that was the issue.  If that's the case, would setting the gain setting low compensate for the cluttered water? And if the oatmeal wasn't the culprit, what would you suspect the problem to be?  I believe the transducer was level, but if it wasn't would that result in false depth readings?

Any help/advice would be greatly appreciated, and thanks in advance!

[dekatronic]

Sometimes you can get false readings if there are a lot of suspended particulates and your sensitivity is too high. Or maybe you're getting interference from other sonars in the vicinity.

Also I found out from my own experience that I get better readings if I lower the transducer at least 6" below the bottom of the ice. Not sure why it improves my readings, but maybe the transducer picks up refracted pings if it's not all the way down the hole.

[RuralMT]

and your sensitivity is too high

Sorry for the ignorant question, but is gain the right term for sensitivity?  And thanks for the suggestion about lowering it below the ice a bit farther.  My transducer is mounted to a bracket on a 2x2, and the stick was just barely long enough to get it just below the ice.  I'll mount it to a longer 2x2 and see if that helps.

[dekatronic]

Gain = sensitivity

And try using a longer 2x2 to see if it helps. Also make sure you don't have any mounting hardware on the 2x2 that can cause obstruction or diffraction of signal. Good luck 

[stripernut]

I use a Garmin 300 on my canoe and thru the ice. If you are getting the Transducer below the ice, you should be OK. It is most likely the Sensitivity. Just turn it down to the point that the screen clears up, drop your jig down and you should see it fall. Make sure the transducer is level, otherwise you may not see your jig... When I have had interference from other units, it shows up as "snow" on the screen, you can still use it, but it is irritating...

[RapShack]

You DON'T need to have your ducer below the ice.  Sometimes the auto range can take a minute, especially if it's been out of the water for a bit.  If there is a bunch of junk in the water and you have the gain set too high that can be a problem as well.  I see you mentioned about "the gain setting low", does this mean you are running in auto gain mode?  If so ditch that, it tends to err on the side of way too much gain, even when set on "auto low".  One thing I do when it won't range is just lift the transducer up out of the hole and drop it back down.  I doubt that actually does anything besides keep me occupied while the machine does it's thing, but it seems to work.  If worse comes to worse you can always set a manual range and adjust your settings to get a good baseline and then try going back into auto. 

[jiignut]

Proper depth range settings?

[RuralMT]

Many thanks to all the recommendations. I tried them all (longer 2x2, manually adjusting to a low gain, bumping the range to about 10 feet below the bottom) and it worked splendidly! Even through an oatmeal-chummed hole, manually tweaking the gain lower cleared up the image.

One thing I do when it won't range is just lift the transducer up out of the hole and drop it back down.

I found myself doing this several times throughout the morning, and it definitely improved the reading. Not sure if I should be doing this, but with the small Kokanee I'm fishing for, I tend to fish down the same hole in which my transducer sits. Occasionally, after landing one, the reading went funky, but simply pulling it up and dropping it back down seemed to do the trick, even when the transducer was still level.

make sure you don't have any mounting hardware on the 2x2 that can cause obstruction or diffraction of signal

.
Do certain metals mess with the reading, or were you saying I might have something blocking the sonar?

Again, many thanks for the help!

[RapShack]

Glad you got it worked out.  If you're liking the Striker and ice fish a lot put the ice ducer on your Xmas list for next year. 

[RuralMT]

Oh, it's on there, along with many other toys. I considered getting it for this season, but as a teacher, I have to buy such things in increments. An electric trolling motor for my canoe is next on the agenda.