Broadband interference

Internet over power lines may jam airwaves, but remedies exist

Amateur radio operators are wary about a new technology that can carry high-speed Internet service via power lines. They say it causes significant interference with their communications and could potentially interrupt public safety operations.

The technology's supporters acknowledge that broadband over power lines (BPL) sometimes creates interference. But they say technology exists to remedy the problem.

BPL bundles radio frequency with electrical currents either through aboveground wires or underground pipes. Because electric currents and radio waves operate at different frequencies, they don't interfere with one another. Customers need to connect only a modem to their outlets to receive the signal.

Manassas, Va., recently installed BPL technology throughout the city, and several hundred residents have signed up for the broadband service. The city's public works department did the installation. Communication Technologies, based in Chantilly, Va., will own and operate the network and provide Internet service.

George Tarnovsky, an amateur radio operator who lives near Manassas, doesn't discount BPL's benefits, but he said it interferes with ham radio signals.

Tarnovsky also said ham radio transmissions could create a dangerous situation if they interfere with BPL transmissions.

"What if you interrupt a BPL transmission, and they're doing voice over IP, and it happens to be an emergency call?" he asked. "This could possibly be a life and death situation. Who's going to be liable for this should something tragic happen?"

Tarnovsky and several ham radio colleagues filed a complaint with the Federal Communications Commission, which asks the two sides to work it out.

Walter Adams, a Communication Technologies vice president, said radio operators have pointed out several instances in which the technology exceeded FCC specifications and caused interference. To remedy those problems, dynamic notching devices were put in place.

"You just block certain portions of the frequency…that is typically in an area where the ham radio people operate," Adams said.

In Manassas, he said the technology shouldn't interfere with the public safety communications equipment, which operates in the 900 MHz range. BPL technology operates in unlicensed spectrum between the 4 MHz and 23 MHz frequencies.

Adams said several federal agencies have expressed concern about possible interference with some satellite-to-ground communications, primarily along the West Coast. The FCC established additional regulations for some geographic areas to address those concerns, he said. He said another group has concerns about possible BPL interference with aeronautical navigational radio.

Adams said amateur radio operators, who are trying to limit interference with their operations, are behind most of the complaints. But he thinks both sides can operate simultaneously.

Alan Shark, executive director of Public Technology, a technology organization that works with several cities and counties, said he is a fan of ham radio operators. But their complaints that BPL technology causes significant interference are misguided, he said.

"This has become almost a religious mantra with the ham operators," said Shark, who has previously led several telecommunications associations, including the Power Line Communications Association.

Shark said interference comes from many sources, and Manassas' BPL deployment minimizes interference because of technology developed by Israel-based Main.net Communications. He added that the FCC and the National Telecommunications and Information Administration have done testing and devised rules and regulations for addressing the interference.

Adams said the FCC offers a prescriptive mandate that states that BPL technology should not harmfully interfere with ham radios.

"It's not a question of whether BPL interferes with ham radios. It does," he said. "But then again so does your garage door opener, so does your diesel engine or your car. It's a question of how harmful it is in terms of how loud it is and how much interference" it causes.

Manassas has the power

Manassas, Va., with a population of 37,000, has installed broadband-over-power-lines technology across its electrical infrastructure. That infrastructure consists mostly of underground fiber-optic cables. Here are some facts about the Internet service that the new infrastructure supports.

  • Potentially, 12,500 households can sign up.
  • So far, 700 customers have subscribed.
  • Residents pay $28.95 a month for access speeds of 300 kilobits/sec to 800 kilobits/sec.
  • Commercial customers pay $39.95 to $79.95 a month for access speeds of 1 megabit/sec to 4 megabits/sec.

-- Dibya Sarkar

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