If your depth finder is experiencing erratic readings, and you have another sonar device running on your boat, then you have sonar cross-talk interference.
There are 2 solutions:
- 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.
- If possible, change the frequency of one of the sonar devices. HawkEye® depth finders typically run on 200 khz, so changing the frequency of the other device on your vessel will greatly help to reduce false readings.