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 Previous: FCC Invites Comments on Additional Morse Code-Related Petitions |  Next: The K7RA Solar Update |
NEWINGTON, CT, Oct 9, 2003--A subcommittee of an International Telecommunication Union (ITU) panel of technical experts responsible for terrestrial broadcasting issues has joined a growing chorus of concern about the interference potential of power line telecommunication (PLT)--better known in the US as Broadband over Power Line (BPL). ITU Radiocommunication Sector (ITU-R) Sub Working Group (SWG) 6E1 expressed the view that interference produced by systems employing PLT as well as by Industrial, Scientific and Medical (ISM) equipment and short-range devices, would compromise broadcast reception.
 BPL would use low and medium-voltage lines like these to distribute broadband services. |
"SWG 6E1 is of the opinion that any increase in the amount of noise due to these systems is unacceptable," said a statement from the group's chairman to the chairman of Working Party 6E (WP 6E). "In particular, broadcast services should be protected from unwanted emissions from PLT systems," the panel asserted, "as these emissions are a byproduct of a system that is not itself a user of the radio spectrum." The panel recommended the formation of a group representing all users of the radio spectrum "to coordinate development of limits to be imposed on the radiation from these systems."
WP 6E says it will continue to study the effects of PLT/BPL, ISM equipment and short-range devices on terrestrial broadcasting and send the results to ITU-R Working Party 1A, which is responsible for spectrum engineering techniques. WP 1A is scheduled to meet in Geneva October 30 to November 5.
ARRL Chief Executive Officer David Sumner, K1ZZ, expressed strong support and appreciation for the SWG's conclusions and the ongoing efforts of parent Working Party 6E to study the issue. "Our studies have shown that the broadcasters' concerns are fully justified," Sumner said. "If BPL is a problem for broadcasters, it's easy to see that it would be a disaster for us," he added, noting that broadcasters' signal strengths typically far exceed those of radio amateurs.
Broadcasters themselves also have exhibited increased concern about the potential of PLT/BPL to prevent their signals from reaching listeners. The Research and Development branch of the highly regarded British Broadcasting Corporation (BBC) has released a White Paper reporting on a brief trial in Scotland. The two competing PLT/BPL systems in operation in the town of Crieff both interfered with HF reception. Tests were conducted at four locations.
"The forms of access PLT that were tested in Crieff were found to have demonstrable potential to cause interference to indoor reception of broadcasting in relevant bands," the White Paper concluded. Before commercially licensing PLT, the report advised, regulators need to undertake further study of other PLT systems and, among other issues, look into possible ways to make the PLT systems compatible with radio reception.
At the first location, a residence, interference from a Main.Net modem was audible even on very strong broadcast signals. Reception was also significantly impaired at a neighbor's house as well as at various locations in the street between the residence and the substation serving it. This was despite the fact that the main distributor cable was underground.
The BBC engineers described the interference as varying between "'annoying' and a level sufficient to make the broadcast completely unintelligible."
At a retail shop where another Main.Net modem was in use, "reception of an apparently strong broadcast signal was badly impaired when the PLT modem was busy," the report said.
Ascom systems were in use at the other two locations. The BBC engineers observed interference to HF broadcasting signals despite the system designers' efforts to reduce emissions in the broadcasting bands.
Field strength measurements taken at three of the four locations showed PLT/BPL emissions far in excess--by as much as 50 dB--of various proposals for limits intended to restrict the degree of interference.
A report prepared by the Australian Communications Authority (ACA), Broadband Powerline Communications Systems--A Background Brief, concluded that "a potential risk to HF radiocommunications services from the widespread use of broadband powerline communications systems" appeared to exist. Citing BPL trials in the US, Europe and Asia, the ACA brief said, "The results of these trials have not alleviated concerns over the potential interference risk to radiocommunications."
The ACA report included the Australian Broadcasting Authority, the Australian Maritime Safety Authority, the Department of Defence and the Wireless Institute of Australia--that country's International Amateur Radio Union member-society--as "stakeholders" subject to potential electromagnetic compatibility (EMC) concerns.
ARRL's comments, reply comments and technical exhibits filed with the FCC in response to the Commission's Notice of Inquiry (ET Docket ET 03-104) are available on the ARRL Web site. See also the article "BPL is a Pandora's Box of Unprecedented Proportions, ARRL Tells FCC". Additional information and video clips are on the ARRL "Power Line Communications (PLC) and Amateur Radio" page.
To support the League's efforts in the BPL
fight, visit the ARRL's secure BPL Web site.
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