Following a safety issued with LED interference of radio equipment identified last year, the Federal Communications Commission and the USCG have updated radio inspection checklists.
The new checklist includes tests for LED lighting interference with VHF radio and Automatic Identification System (AIS). The updated checklists also incorporate changes to regulatory and radio communication services. The new checklist and associated advice are posted on the FCC’s Enforcement Bureau Ship Inspection Checklist website
Last August The USCG released Marine Safety Alert 13-18 describing the potential for radio frequency interference from LED navigation and other above deck lighting to VHF marine radios and AIS.
Radio frequency interference caused by these LED lamps were found to create potential safety hazards. 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.
The safety alert said strong radio interference from LED sources may not be immediately evident to maritime radio users. Nonetheless, it may be possible to test for the presence of LED interference by using the following procedures:
- Turn off LED light(s).
- Tune the VHF radio to a quiet channel (e.g. Ch. 13).
- Adjust the VHF radio’s squelch control until the radio outputs audio noise.
- Re-adjust the VHF radio’s squelch control until the audio noise is quiet, only slightly above the noise threshold.
- Turn on the LED light(s). If the radio now outputs audio noise, then the LED lights have raised the noise floor. (Noise floor is generally the amount of interfering signals / static received beyond the specific signal or channel being monitored.)
- If the radio does not output audio noise, then the LED lights have not raised the noise floor.
If the noise floor is found to have been raised, then it is likely that both shipboard VHF marine radio and AIS reception are being degraded by LED lighting.