RF noise is a frequent discussion topic among radio amateurs. A proliferation of electronics has cluttered and complicated the noise environment; it’s not just power lines anymore. Unless isolated from civilization, most hams experience RF interference (RFI) — sometimes without even realizing it, although spectrum scopes on modern transceivers make RF noise much more apparent. Various approaches to address the apparently worsening noise floor have been taken around the world, some addressing lax regulation.
“We all want to enhance our ability to copy the weak ones by increasing our signal-to-noise ratio,” Alan Higbie, K0AV, said in his March/April NCJ article, “Tracking RFI with an SDR One Source at a Time.” He suggests practical methods for individual radio amateurs to improve their own noise environment. “We can do that by reducing the noise on each band that we operate. Lowering the noise floor increases the relative signal strength of weak signals. Those in typical residential environments find that locating and eliminating RFI sources is a never-ending process. It is much like weeding a garden.”
The International Amateur Radio Union (IARU) warns against complacency. “Radio amateurs cannot sit back, because even if the desired noise limits are agreed, there are many rogue manufacturers and dealers who will happily sell noise-generating devices, leaving out filter circuits to cut costs,” IARU said in a statement. IARU has urged member-societies to get involved.
The FCC Technological Advisory Council (TAC) — a Commission advisory group — initiated an inquiry in 2016 looking into changes and trends to the radio spectrum noise floor to determine whether noise is increasing and, if so, by how much. The TAC had encouraged the FCC to undertake a comprehensive noise study in 1998, and cautioned the FCC against implementing new spectrum management techniques or initiatives without first concluding one. In 2017, the FCC Office of Engineering and Technology (OET) invited comments on a series of (TAC) spectrum-management questions. ARRL, in its comments, took the opportunity to strongly urge the FCC to reinstate the 2016 TAC noise floor study, which, ARRL asserted, was terminated before it even got started. ARRL urged the FCC to “depart from the traditional regulatory model” that placed limits only on transmitters and called for “a ‘holistic’ approach to transmitter and receiver performance.”
Greg Lapin, N9GL, represents ARRL on the TAC and chairs the ARRL RF Safety Committee. “Perhaps the best result that we obtained was an indication that illegal devices, mainly LED lights, were in circulation, and the Enforcement Bureau agreed to look into it,” he told ARRL. “We never heard what they found out, but recently, I was buying some LED bulbs over the internet from a site in Texas, and they were selling non-FCC approved lights — and didn’t seem to care.” Lapin said his complaint went nowhere, and the TAC’s focus has been nudged in the direction of addressing 5G issues.
- ARRL offers a wide range of information on RFI on its website.
- ARRL Northwestern Division Director Mike Ritz, W7VO, will offer a seminar on HF Noise Mitigation as part of the ARRL Learning Network webinar series, on Thursday, April 22, at 1930 UTC).
Some national regulators are paying attention to noise complaints, although not necessarily from users of licensed services. In the UK, regulator Ofcom recently dispatched an engineer just 30 minutes after receiving a report of interference to unprotected license-exempt devices — key fobs in this instance. “On rare occasions, faulty or unauthorized equipment can interfere with nearby technology and prevent it from working properly,” Ofcom said. Unclear is whether interference to licensed services would get the same level of attention.
Participants at the 2017 International Amateur Radio Union (IARU) Region 1 Conference in Germany, devoted considerable discussion to noise issues and the need to monitor the noise floor. The Deutscher Amateur Radio Club (DARC) has been working on developing a noise measurement system that approximates methods used by the International Telecommunication Union-Radiocommunication Sector (ITU-R). DARC reported that 35 of these electrical noise area monitoring systems (ENAMS) have been delivered, and it’s seeking another 20 locations as part of the effort to monitor noise interference on the HF bands. DARC said the ENAMS can help to make scientifically reliable statements about interference levels.
The IARU Region 1 EMC (electromagnetic compatibility) RF Noise Measurement Group meets quarterly to share ideas and experiences. One project under consideration is development of a common database to gather output from various monitoring stations for further analysis.
IARU sees wireless power transmission (WPT) technology as an impending major noise threat, especially from WPT electric vehicle (WPT-EV) charging systems. “For the amateur service, given the planned density of WPT-EV systems, it is calculated that there will be a widespread and serious impact on its operation in the vicinity of WPT systems” from spurious emissions, said a 2019 ee publishers article, written by “Amateur radio societies concerned about the HF noise floor.” The article also said, “To ensure a low probability of harmful interference to radiocommunication services, further study is required, including evaluation of real equipment, mitigation techniques and other measures to improve WPT-EV systems.”
The South African Radio League (SARL) is encouraging radio amateurs to set up their own RF noise monitoring systems using a dongle and a Raspberry Pi. The HF noise monitoring system takes 12 × 1 MHz bandwidth samples every 2 minutes, saving the data to a file.
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