Lowrance LMS-480 DF and radar interferance

[Chica]

Just returned from Vancouver Island where I encountered a problem when my GPS module failed to respond when near boats using their radars knocked my antenna out. ("GPS module not responding") shows up on your screen. If this happens, disconnect the GPS antenna cord, the center one on the back of your unit, turn the unit on, wait a few minutes and reconnect the cable, That's the quick fix. The cure is to have Lowrance send you a MMC and follow the instructions, to re-program your unit. There is no charge for this update as long as you return their card.
I am having trouble with this unit finding the bottom while trolling, even a speeds as low as 1.5 to 2.5 mph. My 90hp is off and out of the water. If not moving it eventually finds the bottom, I'm in water 250' deep. I do not feel that turbulance from the under surface of the boat should be a problem at this speed. The transducer is at or below the bottom of the hull, and a second transducer on an optima seems to track the bottom well. I do not run both at the same time. Any thoughts? Chica

[Sea Wolf]

Was kinda hoping Dusty would kick in on the radar question and maybe the other.

Long time since any posts, Dusty! Hope everything's OK! Joe.