WASHINGTON—It’s high time to take action about all this noise.
So says NAB. The National Association of Broadcasters today urged the Federal Communications Commission to address increasing spectrum noise from manmade sources, and to do so “aggressively and expeditiously.”
“Failure to do so risks devaluing licensed spectrum and drowning licensed users in a sea of noise,” the NAB wrote in a comment filing, calling noise a threat to all radio and TV broadcast services. It wants the commission at least to set emission limits for devices operating on the AM band and to clarify the kinds of good engineering practices that should be followed by the makers of electronics that cause so much noise -- such as switching power supplies in consumer and commercial equipment; power transmission lines; LED lighting including traffic lights; and composite video display systems such as those in Times Square and Las Vegas.
In June, the FCC Office of Engineering and Technology announced that its Technological Advisory Council would begin investigating changes and trends in the radio spectrum noise floor. The council consists of a group of technology experts and provides expertise to the commission.
[See the list of Technological Advisory Council members.]
The NAB welcomed the initiative but lays the initial responsibility for controlling radio noise at the feet of the FCC, saying that the agency was created by Congress to address interference chaos in the first place. “Today’s worsening noise problem threatens to recreate the very disorder that the commission was established to eradicate,” the NAB said.
The association said effective spectrum management must assess both the likelihood of interference and the costs of disrupting existing services.
“Noise is caused largely by the proliferation of cheap and simple electronic designs with little or no regulatory oversight or enforcement. At the same time, the shift of radio communication systems from analog to digital increases, in many cases, the susceptibility of communications systems to such noise interference.” There is also a misperception that digital radio technologies are more robust than analog predecessors. While it’s true that many digital systems can operate closer to the noise floor than an analog counterpart, the NAB wrote, a rising noise floor can offset that advantage.
NAB said AM signals in particular are susceptible but insisted that the commission need not accept the inevitablity of an ever-worsening noise environment.
It also noted problems that arose for FM during the rollout of IBOC digital radio. The commission moved then to set the power level for digital carriers at 1 percent of the analog power level (–20 dB below carrier) — a level set based on “theoretical analysis and laboratory testing that did not adequately consider the effects of environmental noise,” the NAB said. Afterward, many FM stations found themselves unable to replicate their analog coverage with their digital signal. Though the commission did approve blanket authorization to increase IBOC power for most stations, “increasing power to overcome noise is treating the symptom rather than the underlying disease,” the NAB said in its comment filing.
An example of similar issues occurred in 2009 during the transition from analog to digital television. After consumers complained about difficulties receiving VHF channels, the Office of Engineering and Technology discovered that RF interference was resulting from sources. Perfect digital TV reception was then achieved with the elimination of the offending noise source. However, though the FCC established the Replacement Digital Television Translator Service to handle VHF DTV reception issues, the NAB says that the commission has not addressed the underlying noise issues.
“It is simply poor spectrum policy to continue to battle interference with techniques that ultimately create more interference, and does not comport with the general requirement in the Communications Act to ‘use the minimum amount of power necessary to carry out the communication desired,’” the NAB wrote. (The filing did not address a commonly heard gripe from HD Radio critics that, on the U.S. AM band in particular, the digital signals are themselves a source of unwelcome noise and interference.)
The first step, the NAB suggests, is for the commission to address the cause of the problem. It pressed for a review of Part 15 emission limits to determine what improvements are necessary to protect licensed services, and then adopt enforceable limits that will minimize noise interference.
At a minimum, it said, the commission should set radiated emission limits to protect AM stations.
“[T]here are no emission limits for devices operating on frequencies below 30 MHz. This means that the AM band is afforded no quantitative protection at all,” it wrote. “Under Part 18, radiated emissions outside the ISM bands allow for 10 uV/m at one mile and 25 uV/m at 1000 feet. The protected service contour for AM coverage by most stations is 0.5 mV/m,while the interference protection ratio for groundwave-to-groundwave is 20:1.By adopting and enforcing radiated emission limits of 0.025 mV/m, measured at a distance of 10 meters, the FCC could eliminate much of the interference that exists today and better protect stations in the AM service.”
It also asked the commission to clarify the meaning of “good engineering practices to minimize the risk of harmful interference,” a phrase in the rules covering makers of incidental radiators. “The commission provides no guidance as to what constitutes ‘good engineering practices,’” the NAB wrote. “Absent any further guidance, this rule is largely meaningless and unenforceable in practice.”
Also, NAB noted that for in the case of devices, there is an incentive to cut costs by removing RF-suppression equipment that does not affect day-to-day operation. “At present there is no requirement for a post-market sampling or measurement program to detect such modifications. Either the manufacturer or the FCC, or both, need to have a robust enforcement program that includes sampling of retail products for compliance.”
In short, the commission’s existing limits on intentional, unintentional and incidental radiation are inadequate to protect licensed radio services, particularly broadcast services. “We urge the commission to undertake a comprehensive review of these limits and develop specific and enforceable limits to prevent further noise interference.”
This story first appeared on TV Technology's sister publication Radio World.
Michael Balderston contributed to this story.
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