I never see arches on HB 688

I fish a lot and use my HB 688DI exclusively. I never see the arches that signify fish. Last week I was in a lake with lots of big walleyes, northerns, bass and didn't see one arch. I had my fish alarm on and set for large fish only and it would beep at me. It would show a fish in the middle of my depth range with the number (depth) next to it, but the shape was not an arch. I hate to use the fish id but with the lack of arches I wanted to see where the fish were.

Is the arch a factor of chart speed and sonar sensitivity? I have made several different adjustments to speed and no difference.

I am home now and may not get out until next week. In May I was with a guide in South Dakota and I saw all kinds of arches on his screen.

Thoughts?

Hope this helps you with the seeing arch problems.

http://www.humminbird.com/Category/S...AQ/FishArches/

https://www.youtube.com/watch?v=Pm1dC3l9xEA

https://www.youtube.com/watch?v=fSMvq6QrjOs

Scrat has provided some very good references ...
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The biggest detriment in obtaining fish arches in the HB DI unit is the narrower sonar cone angles (as compared to the other HB Dual Beam Sonar cone angles) ...

The other HB Dual Beam units have a 20° 200kHz Sonar cone and a 60° 83kHz Sonar cone ...

The HB DI units have a 16° 455kHz Sonar cone and a 28° 200kHz Sonar cone ...

That's just not a wide enough cone angle for the fish to be at different distances from the xducer while in the narrow Sonar cone (as we know that the arch is created by the fish being farther away from the xducer at the edges of the Sonar cone than when the fish is in the center of the Sonar cone) ...

http://i477.photobucket.com/albums/r...B/colrmako.gif

Rickie

Thanks, so if I stay in the 200mhz frequency i am more likely to see more of an arch as it is the wider field. I like the resources Scrat provided as well.

Thanks guys.

Quote:

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Originally Posted by Royalwapiti

Thanks, so if I stay in the 200mhz frequency i am more likely to see more of an arch as it is the wider field. I like the resources Scrat provided as well.

Thanks guys.

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Correct ... The wider the Sonar cone - the more likely it can paint an arch ...

Rickie