I wondered which one is best and clearest for the down and side imaging, I really enjoy the side and down imaging the most. I think all are max of 150' on di and si.
ONIX has a dedicated DI piezo for true dedicated DI imaging ...
HELIX does not have a dedicated DI piezo ...and computer generates the DI image from the SI data just like all othe HB core Series SI units in the past ...
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Some say ONIX SI is better than core units - some say ONIX SI is about the same as core units ...
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Maximum SI Range is dependent in large part by the water depth and bottom composition being scanned ...(hard bottoms reflect Sonar much more efficiently than soft bottoms) ...
Rickie