Unfortunatly they could all be right on , but only one with your electronic's with you boat. Test by Turning one off , do you see the same prior to shutting down the other unit ? Do the Same with the other. I run a Lowrance LCX18, LCX25, LCX110, Fish Hawk 840, Humminbird 997. For most times I get great readings with minimal interference. I have the Lowrance on the Left Side of the Transom and the Humminbird & Fish Hawk on the Right Side, Both units can also be on the Bow trolling motor.