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How Broadband Over Powerlines Works


On April 23, 2003, the FCC put forth a Notice of Inquiry to the public supporting the potential of the BPL technology and seeking to set standards in practice for its implementation. Immediate opposition came from the American Radio Relay League (ARRL) and the Federal Emergency Management Agency (FEMA). Both entities claim that BPL will cause serious interference issues.

A BPL modem is considered an unlicensed device, like a cordless phone or garage door opener. All unlicensed devices are governed by the FCC's Part 15 rules. Part 15 mandates that all electronic devices sold in the United States must meet FCC radio-frequency emissions limits. These limits are in place to secure against interference with important transmissions like CB communications, air-traffic control and government channels. ARRL and FEMA are concerned about the interference caused by BPL signals transmitted on exposed medium-voltage power lines.

Cable TV operators get around the interference problem by shielding all of their cables. "Coaxial cable" used by cable TV operators has a braided metal shield that surrounds the signal wire. Telephone cables are also shielded. Power lines, on the other hand, have no shielding. In many cases, a power line is a bare wire, or a wire coated in plastic. The lack of shielding is where the interference concern comes from.

Depending on the bandwidth the FCC allots for BPL, interference with other radio services may be a problem. Currently, the frequency band breaks down as follows:

  • AM radio - 535 kilohertz to 1.7 megahertz
  • Short-wave radio - 5.9 megahertz to 26.1 megahertz
  • Citizens-band (CB) radio - 26.96 megahertz to 27.41 megahertz
  • Television stations - 54 to 88 megahertz for channels 2 through 6
  • FM radio - 88 megahertz to 108 megahertz
  • Television stations - 174 to 220 megahertz for channels 7 through 13

While FEMA is wiling to allow the FCC to seek a compromise, the ARRL claims that compromise is not possible because the bandwidth needed for BPL will directly interfere with ham radio and short-wave radio transmissions. Developers of BPL say that these interference issues have been solved. Only tests and time will tell. Until then, the advancement of BPL moves forward slowly as it waits for standards and logistics to be decided by regulating bodies.

For more information on BPL, other Internet connection methods, and related topics, check out the links on the next page.

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