Interference questions dog broadband over power lines

IDG News Service - Ham radio operators and at least one U.S. federal agency contend that the transmission of broadband over power lines interferes with their radio signals, and if the radio operators have their way, the emerging technology that's meant to give Internet users another broadband service choice might not get off the ground in the U.S.
The American Radio Relay League (ARRL), a national ham radio association, and the Federal Emergency Management Agency are among the organizations that have raised concerns with the Federal Communications Commission over possible shortwave radio interference caused by broadband over power lines, often called BPL.
Companies experimenting with BPL, which uses traditional power lines to transmit data over the Internet, have promoted it as an inexpensive-to-deploy alternative to cable-modem or Digital Subscriber Line services.
Some BPL supporters champion it as a way for broadband to reach rural and other areas with limited broadband service because of the near ubiquity of power lines.
The two sides are far apart on the interference issue, which the FCC is examining in a request for public comments that has been ongoing since last April. The ham radio association says it has found radio interference in every place it has tested short-wave BPL systems, while representatives of the BPL industry say they can't find interference caused by their systems.
The FCC's rules already prohibit unlicensed electronic devices, including BPL transmitters, from interfering with licensed devices, such as ham radios. If the FCC were to find interference and enforce its existing rules, most of the BPL industry could be shut down. "If the commission were to follow its rules, that would be the practical effect," said Dave Sumner, CEO of ARRL. "If the commission decides that BPL cannot operate in this country, that'd be fine with us."
Most BPL vendors use devices called repeaters to amplify and clean up the data signal carried on power lines, and those devices, as well as BPL modems, emit frequencies in the same range as radios used by ham radio operators and some emergency responders, according to the ARRL. Some BPL vendors are experimenting with devices that use microwave signals; the ARRL says those devices wouldn't interfere with ham radios.
But Current Technologies LLC, which offers BPL service in the Cincinnati and Rockville, Md., areas, can't find interference caused by its system, said Jay Birnbaum, the company's vice president and general counsel. Current Technologies uses a technology standard called HomePlug, designed to not interfere with other radio signals.
"[Interference] just doesn't exist," Birnbaum said. "They based a