Topic 07 - Are nearby vessels interfering with your fish finder?

When two or more echo sounders are operating in close proximity and at the same or similar frequency, it is possible for each to receive false returns from the others transducer. In such cases the operator will see noise and clutter, false returns, dotted lines, multiple bottoms or other video anomalies on the screen. This is most common in and around marinas or harbors where there may be multiple fish finders operating at the same frequencies.


In order to get rid of interference, there are a couple of different solutions to try; One way is to shift the frequency emitted from the fish finder’s transducer, if possible, in order to avoid interference. Another way is to turn on the interference removal function on your fish finder. Furuno fish finders have interference rejection circuitry which can be used in such instances, but use it sparingly to avoid eliminating small targets. Interference rejection will automatically try to change your fish finder’s transmission cycles, resulting in less interference.


Most of the time fish finder interference is caused by signals transmitted from nearby boats, but in some cases it can also be caused by electronics on your own boat. Make sure that your electronics are properly grounded, and avoid running electrical cables alongside your transducer cable.


If previous solutions yield no results, you may try to manually change between low and high frequency on your fish finder to see if the interference disappears. If this still does not help, you may need to distance yourself from other vessels.


Interfering signals from nearby vessels

Whenever other boats are close by, your fish finder might receive interference. Diagonal lines and noise such as spots might appear, making the video presentation difficult to read.