Radio amateurs frequently complain about increasing noise from a variety of sources, so it should be welcome news that the FCC Technological Advisory Council (TAC) — an advisory group to the FCC — is investigating changes and trends to the radio spectrum noise floor to determine if there is an increasing noise problem, and, if so, its extent. The FCC Office of Engineering and Technology (OET) announced the TAC study this week in a Public Notice and invited comments and answers to questions that the TAC has posed in the notice. The comment deadline is August 11. The TAC said it is trying to determine the scope of any noise issues and has invited “quantitative evidence” of noise problems, as well as recommendations on how to perform a noise study.

“The TAC is requesting input to help answer questions about the study of changes to the spectrum noise floor over the past 20 years,” the announcement said. “Noise in this context denotes unwanted radio frequency (RF) energy from manmade sources. Like many spectrum users, TAC members expect that the noise floor in the radio spectrum is rising as the number of devices in use that emit radio energy grows.”

The ARRL representative on the TAC, Greg Lapin, N9GL, co-chairs the TAC Spectrum and Receiver Performance Working Group with Lynn Claudy of the National Association of Broadcasters. Lapin also serves as chairman of the ARRL RF Safety Committee.

The TAC said that its search for “concrete evidence of increased noise floors” has turned up only “limited available quantitative data” to support its presumption of a rising noise floor. The TAC said it wants to find ways to add to the available data so it can “answer important questions” on the topic for the FCC.

The TAC noted that many types of devices generate radio spectrum noise. In the case of incidental radiators — devices not designed to emit RF but do so anyway — there is little regulation governing such noise. “Most electric motors, light dimmers, switching power supplies, utility transformers, and power lines are included in this category,” the TAC announcement explained.

Devices designed to generate RF for internal use, or send RF signals to associated equipment via connected wiring, but which are not intended to emit RF energy, are called unintentional radiators. This category includes computers and many portable electronic devices, as well as many new high-efficiency lamps. FCC regulations limit the levels of emitted RF energy from these devices.

A third group of devices categorized as intentional radiators (unlicensed and licensed) and industrial, scientific, and medical (ISM) radiators — are designed to generate and emit RF energy by radiation or induction. Intentional radiators include cellular phones and base stations, unlicensed wireless routers, Bluetooth devices, broadcast TV and radio stations, and radar systems. Amateur Radio transmitters also fall into this category. Microwave ovens, arc welders, and fluorescent lighting are examples of ISM equipment.

“Such emitters contribute to the noise floor with emissions outside of their assigned frequencies,” the TAC said. “These are sometimes generated as spurious emissions, including, but not limited to, harmonics of desired frequencies and intermodulation products.” FCC regulations permitting the operation of these devices specify emission limits outside of the device’s licensed or permitted operating frequencies.

The TAC said that responses to the questions it has posed in the Public Notice will help it to “identify aspects of a study to determine trends in the radio spectrum noise floor.” The Public Notice includes information on all methods of responding to the inquiry. The ARRL is planning to comment.

For more information, contact Greg Lapin, N9GL.