Identifying RFi (Radio Frequency interference)

[Derek - Raymarine - Moderator]

Radio frequency Interference (RFi) can affect any installation and can very from boat to boat, although in fact it only affects a small proportion of boats and installations. Some boats may be heavily affected, yet others - which could be the same type and have equipment installed in exactly the same way, are completely unaffected.

RFi is generally high frequency signals emitted by 3rd party sources affecting the operation or performance of the electronic equipment onboard. Most equipment has some form of shielding or grounding to protect against this effect, but this can only offer limited protection depending on the frequency and amplitude of the RFi

RFi can also be caused by ESD (ElectroStatic Discharge), such as near lightning strike or EMP (ElectroMagnetic Pulses)

RFi can be generated by many different sources and can affect a system in many different ways, so a steady process of logical elimination is required, also what may solve the problem on one boat will not necessarily work on another. Each case is individual and specific to the boat, the installation, the cabling and small variances in cable runs, location of product, grounding and connection of drain wires should all be checked.

RFi can be induced in a system through three main routes, Conducted, Induced and Radiated

Conducted RFi is where the interference is triggered in the cables by equipment connected to the cables, it can be triggered by operation of reversing motors, switching systems, battery chargers, inverters, in fact anything that is electrically powered. Simple solutions such as fitting ferrites can often resolve the issue directly,
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Another simple solution such as checking the drain wires and correct grounding could also be used,
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In all cases of conducted interference, temporarily powering the affected equipment from a completely isolated power source, (a well charged battery is best), will confirm if this is the cause.

Induced interference is where the source of interference is not directly connected to the affected equipment. This can happen when cables are bundled together in a loom, so if some of the cables are carrying high power signals or large reversing currents they can emit strong enough signals which will then be picked up by adjoining cables and the interference will then be imposed on the adjoining cables. checking the solutions suggested above may help.
In severe cases, sleeving the affected cables in a braided metallic sheath, which is then bonded to the ground dynaplate will offer good protection against induced RFi
Separating the relevant cables by 6" or more will usually eliminate the effect of Induced interference.

Radiated interference is the result of equipment emitting airborne signals which trigger erratic operation or faults in the equipment that it impinges on. It can be caused by poor quality vhf Cable connectors or cable, poorly screened or Earthed vhf or SSB transmitters or even faulty equipment. Isolating the source will identify the cause and indicate the appropriate solution, for example replacement cables, relocation of antenna, improved grounding or replacement product.

In all cases, it is likely that assistance may be required, the local Raymarine dealers are better equipped to perform this service … we recommend consulting your dealer prior to bringing equipment to the dealer.
Alternatively please contact Certified Raymarine Installers
If the product is faulty, then contact Raymarine’s Product Repair Center.


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