Probably not what you want to hear but I was running my sonar on a 1242 from the built in transducer on my Ultrex. Major interference while the HB unit running a transducer on the bottom of the motor was clear. Just for curiosity I hooked the HB unit into the same built in transducer and it was clear also. Apparently the garmin is picking up rfi the HB is filtering out. My Livescope is clear however.