[Capt. Debbie]

The frequencies create two distinctly different look down cones. So lets say in 20 feet of water the transducer in looking at a 15' circle. While that same freq in 200 feet of water is looking a 200 foot wide circle.

The deep frequency had a much tighter cone so that in 200-300 feet of water it is only a 50 foot wide on the bottom. Problem is, that it's narrow so can easily miss stuff not directly underneath it is shall water where the cone may only be a few feet wide.

And remember CHIRP stuff is digital smart processing by the machine trying to figure out what it is seeing. Not the transducer.

And true 3D is usually two transducer, like our own two eyes to get depth perception.