The SI slice beam sound pulse is strongest along its "Main Axis" and weaker at the outer fringes of the SI slice beam directly under the boat ...


This weakening of the outer fringes of the SI slice beam will be more evident with the 800kHz simply because higher frequency sound wave attenuates (absorbs into the water) quicker than lower frequency ...(leaving less energy to be reflected off actual targets - especially in the outer fringes of the SI slice beam) ...

Rickie