sounder help please

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gday i have a cheap hummin bird matrix15 just wondering if anybody can tell me if 1 -20 is small to big but main question why some show black and some black outline (hollow) of the fish its got me buggerd

[beats]

Not sure about the 1-20 bit, but the sounder u are using from memory has a multi beam transducer, the solid symbols are in the center beam & the outlined ones are in the outer beams, on some the ones facing left are in the left beam & the ones facing right in the right beam.

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cheers mate