If your unit has interference with nothing other than another sonar running in your boat, then you have sonar cross-talk interference. For most depth finders, the only real solution is to move the transducers further away from each other. This can help keep the transducer cones from intersecting, but because cones get wider as the depth increases, the problem can not usually be totally solved by position only. You may need to run one sonar device at a time. Changing one of the sounders to another model that runs on a different frequency than the first will solve the problem.