Fish finder and sonar interference: With the advent of color fish finders and plotters, high definition displays, gps, auto pilots and so on. Electrical interference most commonly described as inaccurate bottom signals and display clutter or lines. Has been an ever increasing problem. Installing these high tech gadgets doesn?t take a rocket scientist but it does take some planning. As electronics become more complicated they also become more sensitive to rfi and emi interference. {Radios, cell phones, alternators ext.} The most common cause of interference is the power supply or the lack of it. In particular the ground path. I have had many a customer purchase sonar units and install them on there own. Only to come back a week later cursing and swearing because the unit keeps acting up. My first question is always the same. { How did you power the unit?} The standard response is I hooked to the fuse box, or I found the nearest 12 volt power and tapped into it. This may work fine for your low end electronics that look like an Atari video game, but with the high resolution monitors and the dual freq. transducers on the market today it just wont do the job. You are looking for an interference nightmare. Your screen is going to look like the last EKG you had during your last stress test. I cant stress enough the need for a dedicated power and ground system for your electronics. Keep in mind that electricity is lazy it will find the shortest path to ground that it can no matter what the consequinces.The end result is interference. Below is an example of voltage drop in a typical fish finder/sonar installation. Bare in mind that this is a dedicated installation. Imagine the drop and interference you may experience if you hooked into the boats fuse panel, which by the way in most boats is only powered by a ten gauge power and ground.. An example of the amount of voltage drop in an average fish finder/ sonar installation might surprise most. Keep in mind this voltage drop was taken from a dedicated power circuit. Meaning the sonar was the only electrical load in the circuit. We used 14 gauge copper wire for the power and ground circuit made a 20 foot run direct to the battery with a 5 amp fuse. We measured a 4.4 Percent voltage drop over the circuit. The end voltage was around 11.48 Volts. Using the same scenario but with 8 gauge wire we had substantially better results. 1.07 percent drop and an end voltage of 11.87 As you can see when it comes to electricity BIGGER is better. Although there are many possible causes of interference this the most common. If after this and contacting the manufacture then replacing the transducer, fish finder head unit, which is the manufactures standard practice. Come back and read section two. Other causes of interference,.