How to Stop Electronic Interference

Tips for curing common electrical-interference symptoms.

March 8, 2013

RFI, “radio frequency interference” or “electrical noise,” on a boat can severely affect the operation, performance and enjoyment of electronics. Here are some common electrical-interference symptoms, causes and possible cures.

You’re receiving reports that your radio transmissions are noisy.

Cause: It could be your inverter or battery charger. Confirm this by monitoring the radio transmissions with a hand-held radio.


Cure: A power-line noise filter connected to the radio’s 12-volt leads can suppress the noise. Connecting the radio to a separate isolated battery source may also solve the problem. Alternatively, you may have to turn off the offending instrument when transmitting.

Your radio is picking up excessive “cross talk” from interfering radios operating on different channels.

Cause: This occurs in areas with a lot of radio traffic.


Cure: Shakespeare ( has two antennas (5225-FLT, 8 feet, $345; 5018-FLT, 17.5 feet, $689) that help filter annoying interfering signals.

Your GPS/chart plotter, radar or other device shuts down when starting the engines.

Cause: Sudden voltage change can mess around with electronics.


Cure: Newmar’s NS-12-­20 StartGuard ($200, serves as a noise filter and temporary backup battery that protects electronics when a sudden voltage change occurs.

Your compass changes its heading when certain equipment is turned on.

Cause: Electrical wiring running near the compass.


Cure: Move wiring farther away from the compass.

Two fish finders are on board but neither works.

Cause: Two fish finders or depth sounders operating on the same frequency can interfere with each other, making them unusable.

Cure: Some models allow you to turn off one frequency, so each set can run on a different frequency.

Noise Demons
Other causes include refrigerator motors, fluorescent and LED lighting fixtures, alternators, ignition systems, computers, monitor screens and even cell phones.


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