The FCC’s Office of Engineering and Technology (OET) has clarified that all RF LED lighting devices falling under Part 15 rules as “unintentional radiators” must meet conducted and radiated emissions limits set forth in those rules.
“Operation of Part 15 unintentional radiators is subject to the condition that no harmful interference is caused,” the OET reminded, in a knowledge database paper released on June 17. “Manufacturers and users should therefore note that lighting devices are required to cease operation, if harmful interference occurs.”
The OET said radiated emissions measurements must be performed at least from 30 MHz to 1000 MHz to adequately demonstrate compliance with Part 15 (§15.109). Its guidance, the OET continued, applies to RF LED lighting devices that, in the past, have been considered to operate on frequencies below 1.705 MHz. Previously, devices operating between 9 kHz and 1705 kHz had to be tested only for radiated emissions up to 30 MHz, where no specified radiated emissions limits exist, and were exempt from testing from 30 MHz to 1000 MHz. The OET said it recognizes that routine radiated emissions measurements are needed under Part 15, based on the highest frequency generated or used in the device.
“[W]e have found that emissions from RF LED lighting devices are non-periodic, broadband in nature, and are produced as a byproduct of the internal driver circuitry within the RF LED lighting device,” the OET “knowledge data base” paper said. “These types of emissions have adequate energy and potential to generate radiated emissions well above 30 MHz.”
The ARRL Lab’s Electromagnetic Compatibility Engineer Mike Gruber, W1MG, said he was pleased to see the FCC’s OET clarify the test measurement requirements. He said ARRL is generally hearing more RFI complaints stemming from RF LED bulbs.
“Not only are the emissions limits higher for Part 15 LED bulbs — as opposed to Part 18 fluorescent and CFL bulbs, they seem to be winning out in terms of consumer popularity,” Gruber said. “Higher limits and more bulbs probably make for more complaints.” Gruber said the Lab has seen LED lighting devices causing problems in the 2 meter band. “Since conducted emissions limits do not apply above 30 MHz, radiated emissions limits can be the first line of defense against RFI at these higher frequencies.”
Gruber pointed out that noise generated by street and traffic lighting can be widespread. In such instances, he suggested that Part 15b limits for residential areas should apply. “These limits are lower than Part 15a limits, which are intended only for commercial and industrial environments,” he explained. “This is especially critical in cases where a pole transformer connected to the lighting device also feeds a home or residence. The 240 V split-phase secondary system can conduct RF into a residence through the service entrance panel.” He suggested that the lower limits may benefit mobile users.
The OET noted that the ANSI Accredited Standards Committee C63® -EMC standards development committee is drafting measurement procedures for lighting devices. “When complete, we expect it will address in greater detail the measurement procedures and configurations to be used in determining compliance,” the OET said.