This is from MK's FAQs.
What is the cone angle for Minn Kota’s Universal Sonar 2 transducer?
There are several different methods of specifying transducer cone widths. In electronic terms, the decibel is used. By measuring the power level from the center axis of the transducer to the point at which power drops by one half, an accurate cone angle can be measured. Minn Kota’s cone angle measures 20 degrees for the 200 kHz beam and 60 degrees for the 83 kHz beam.
Fair Winds and Following Seas
Bill H. PTC USN Ret
Chesapeake, Va