got a new boat that has a fortrex with tranducer in trolling mtr. it is a dual beam trans ducer. i know the rule of thumb is on a 20 degree cone is 1/3 depth. 10' = 3.3' of bottom. is there a rule of thumb for a 60 degree angle? is it x 3? 10' = 9.9' of bottom. i have fancy stuff but a generic brain. hoping i can catch up someday.

It's a little more than the depth.

60 degrees is about 1 1/2 times the depth at the spec -10db strength.

The actual coverage of 83 kHz is a lot more at lesser strengths.

That applies to the 200 kHz 20 degree coverage that is about 1/3 of the depth at -10 db.

I'll post a coverage chart later for both cone angles. I have to get those loaded to Photobucket.

thats what i am asking. is it frequency or what? where can i go to find out?

60 degrees is about 1 1/2 times the depth at the spec -10db strength.

The actual coverage of 83 kHz is a lot more at lesser strengths.

That applies to the 200 kHz 20 degree coverage that is about 1/3 of the depth at -10 db.

I'll post a coverage chart later for both cone angles. I have to get those loaded to Photobucket.

thanks! like i said before. simple minds need simple solutions.

60 degree cone covers about 11.5' of the bottom at 10 feet of depth.

The formula is tan(1/2 angle of cone) x depth = bottom then multiply by two. Easy to figure out with a scientific calculator. For example.

For 10' depth and a 20* cone

Tan(20/2) x 10' = 1.76 x 2 = 3.52' bottom coverage

For 10' depth and a 60* cone

Tan(60/2) x 10' = 5.77 x 2 = 11.54'

thanks for the info fellas. help me out alot. i appreciate you taking the time to help. its nice to have a place to go to get honest answers and opinions. do not do alot of internet stuff, but this website is the best ive found for friendly and informed people. once again, thanks

Oops, my graph didn't copy over like it should have...

Wayne, your calculations are a little off, esp on the 60 degree cone...

They are not my calculations.