Broadband over Power Line: Is it Interfering?

Shout “Competition!” in a roomful of cable technology people and the thoughts that first jump to mind are likely to involve fiber to the home and satellites. It’s doubtful that many will think first of power grids. But say “broadband over power line” (BPL) to those same people, especially if they’re RF savvy, and you’d have another response. The one word you’d hear would likely be “interference.” The right crowd may even shout it and throw a flag at the same time. That’s not to say that power companies involved in BPL won’t, in time, be serious competitors to cable. The industry’s strategists surely have Duke Power and other such utilities on their competitive matrices. It is rather to suggest that when the BPL industry gathers, as it’s doing this week at a conference in Charlotte, N.C., what cable folks are most interested in learning is whether the interference radiated from broadband-enabled power lines is going to find its way back into the reverse path of cable plants. It’s not supposed to, of course. In the FCC‘s Memorandum Opinion and Order, adopted Aug. 3, which largely overrode calls for reconsideration and reaffirmed its early position of support for the deployment of BPL, the FCC nonetheless maintained that BPL providers must not interfere with existing radio services. Authorized equipment And the FCC actually has a test regime in place. Just last week it issued a “grant of BPL equipment authorization” to Ambient Corp. for its communications node technology. These grants involve both lab and field tests. But do such tests allay the concerns of those in the “existing radio services” business? “Absolutely not,” says Ed Hare, laboratory manager of the National Association for Amateur Radio (ARRL). Deployed BPL can “increase local noise by 40 to 60 dB,” he says. “That’s a lot.” In his last visit to an Ambient deployment site in Briar Cliff, NY, Hare said he found diminished noise, but still registered greater than “S-9,” a level that he assured me would generate consternation among amateur (aka “ham”) radio operators. On the other hand, in a deployment in Cincinnati involving technology from another vendor, Current Technologies, the picture looks somewhat different. “So far, we have not seen major interference problems for that system,” says Hare. Of course, it’s one thing to interfere with amateur radio and another to dirty cable’s upstream path. “My guess is that there will not be major interference problems (on a cable plant) unless you have a pretty serious leak,” says Hare. “Everything that keeps you in, keeps them out,” he says. Jonathan Tombes