Ask Ken: Eliminating Electrical Noise Interference

Maximize the performance of your marine electronics by eliminating interference.
Eliminating Electrical Noise Interference
Eliminating Electrical Noise Interference Boating Magazine

Q. How do you silence electrical noise interference?

A. Here are six tips for eliminating electrical noise interference:

1. Insert an in-line noise filter (starting at $52, in the power leads of the equipment causing the noise (if known) and the device suffering from noise.


2. Keep transducer and antenna cables separated from power wires and never bundle them together. Do not run wiring in close proximity to your engine. The use of shielded wires can eliminate or reduce electrical interference.

3. Clamp-on ferrite-core filters can be effective in countering electrical interference. They are inexpensive ($2 to $6) and simple to install by clamping around the wires and cables of the equipment experiencing and causing noise.

4. Moving or relocating equipment often solves interference problems.


5. Disconnect, move or lay down the antenna(s) to determine if the noise is reduced or eliminated. Antennas placed too close to each other can cause radiated interference.

6. Connecting a ground wire from the metal chassis or grounding stud of a radio or other instrument to the boat’s ground can also minimize or eliminate electronic interference problems.

Eliminating Electrical Interference
Interfering noise on a boat can severely affect the operation, performance and enjoyment of your electronics. Be aware that electrical noise interference can come from a wide variety of sources, including battery chargers, engines, generators, alternators, inverters, air conditioners, refrigerators, tachometers and sensors of all sorts.


Lighting sources and their control circuits, such as fluorescent and LED lights, can be the cause of noise. Even personal portable devices, such as computers, tablets, smartphones, TVs and screen monitors, can contribute to electrical interference. In fact, most anything containing a power supply or microprocessor can be a source of electrical noise.

Here are some noise-suppression tips:

Isolate the Problem
Turn off each onboard electronic and electrical device one at a time. Switch off every circuit breaker or power switch. Shut down your engine(s). Notice if the interference disappears or continues.


Ask Questions
Is noise present only when at the dock, underway or at high speeds? Are the wires of the equipment causing and experiencing noise running parallel or bundled together? Are their antennas mounted near each other?

Play Detective
Does moving or relocating equipment, even temporarily, reduce interference? Disconnect the antennas of any gear experiencing interference to determine if the noise disappears. Often a portable AM broadcast radio tuned in between stations can be used as a “Geiger counter” to pinpoint a source of noise as you move it about the boat.

Radios: Alternator noise can be heard in radio and stereo equipment as a high-pitched whine that increases as the engine speed increases. A 0.5-microfarad, 50- to 100-volt, 40-amp coaxial capacitor ( or an alternator filter can be installed on the alternator to suppress the interference. The capacitor can be soldered across the speaker leads or terminals. If room allows, a terminal strip can be secured in place and used to mount the capacitor’s leads. Two wires can then be run from the terminal strip and connected to the terminals of the speaker.

Popping sounds heard on your radio is caused by your engine’s ignition system. Replacing your spark plugs with resistor spark plugs and resistive ignition wire can silence ignition noise (check with the engine maker before changing plugs).

Often a 0.01-microfarad capacitor ( connected across the two leads of a radio or stereo speaker will eliminate noise caused when transmitting on a radio. This also works when your instrument gauges experience erratic fluctuations when talking on the radio.

Radar interference caused by nearby radars (seen as rotating pinwheels) can be eliminated by activating your radar’s IR, or interference rejection, control. Radars can be affected by rain or white caps when in rough seas, which can create multiple false echoes on the screen. Be sure your Sea Clutter and Rain Clutter controls are turned on or set to automatic.

With fish finders, improper transducer placement can cause turbulent water flow across the face of the transducer, resulting as false echoes on a fish finder when underway. Follow transducer installation instructions carefully in regards to transducer placement. Transducer high-speed faring blocks help create a smooth flow of water over the transducer, minimizing noise on a fish finder.

Tip: Twisting power or multiconductor wires along their entire lengths can help suppress electrical interference. Pre-twisted wire can be purchased too.