06/30/2016
The FCC's Office of Engineering and Technology (OET[1]) has clarified[2] 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.
[1] https://www.fcc.gov/engineering-&-technology
[2] https://apps.fcc.gov/kdb/GetAttachment.html?id=K0pZdRE7biF3aqgO4XZ8cw%3D%3D&
amp;desc=640677%20D01%20RF%20LED%20LIGHTING%20v01&tracking_number=20518
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