I have recently installed a Garmin 240 blue f/f that uses a dual frequency transducer. The Garmin operates at 50 and 200kHz. Rather than remove my Hummingbird f/f that operates at 200 and 455kHz., I would prefer to keep it as a back up or replace the transducer with a side scanning unit that works at a freq. of 455kHz.
Has anyone tried any of these combinations of transducer frequencies with any success? How much seperation between the different operating freq. do you need to avoid interference?