The US Coast Guard says it’s received reports from crews, ship owners, inspectors, and other mariners regarding poor reception on VHF radiotelephone, digital selective calling (DSC), and automatic identification systems (AIS) when in the vicinity of LED lighting systems. This could include interior and exterior lighting, navigation lights, searchlights, and floodlights found on vessels of all sizes.

“Radio frequency interference caused by these LED lamps [was] found to create potential safety hazards,” the Coast Guard said in an August 15 Marine Safety Alert. “For example, the maritime rescue coordination center in one port was unable to contact a ship involved in a traffic separation scheme incident by VHF radio. That ship also experienced very poor AIS reception. Other ships in different ports have experienced degradation of the VHF receivers, including AIS, caused by their LED navigation lights. LED lighting installed near VHF antennas has also shown to compound the reception.”

ARRL has determined a wide range of interference-causing potential from consumer lighting devices.

“While some are relatively quiet, other devices — even those that meet the required FCC emissions limits — can still cause harmful interference,” said ARRL Electromagnetic Compatibility Engineer Mike Gruber, W1MG. “My best recommendation is to try LED lights before you buy, especially if there is a possibility that the device will be used while you’re operating. “Once you have determined that a particular LED device is quiet, then purchase as many as you need from that same store.”

Over the past few years, ARRL has provided the FCC with reports of LED and other lighting systems that are not in compliance with FCC regulations. In several instances, these devices greatly exceeded the FCC's emissions limits, in one case by as much as 58 dB, creating as much noise as 650,000 legal devices.

“Several recent FCC enforcement actions involving LED manufacturers have been encouraging,” Gruber said. “These actions can and will make a difference. I would also like to emphasize that the ARRL remains committed to working with both the FCC and manufactures help facilitate that positive difference in any way it can. It is possible for LED and other lighting technologies to coexist with both amateurs and other users of the radio spectrum.”

The Coast Guard said that, while radio interference from LED sources may not be immediately evident, it’s possible to test for it through several steps, including turning off all LED lighting systems on board to see if the interference disappears. The Coast Guard suggested adjusting the VHF radio’s squelch just to the point where it cuts the audio on a vacant channel. If the noise returns, LED lights have raised the noise floor.

If this is the case, the Coast Guard said, it’s “likely” that shipboard VHF radio and AIS reception are being degraded by LED lighting. The Coast Guard has asked mariners experiencing this problem to report their experiences to the Coast Guard Navigation Center, selecting “Maritime Telecommunications” from the menu on the left and providing details on the online form. — Thanks to gCaptain.com and Frank Smith, WS1MH