FCC commissioners need to do a better job justifying the agency’s rules governing broadband-over-power-line (BPL) emission levels, according to a federal appeals court.

In a ruling last week, the U.S. Court of Appeals for the D.C. Circuit ruled in favor of the amateur-radio organization ARRL on two items regarding the FCC’s BPL rules, requiring the agency to disclose the entirety of its BPL field tests cited in the rules and to explain its reasoning for emission-level limits.

ARRL CEO David Sumner said the court’s decision to have the FCC revisit the emission-level rules was particularly significant.

“It’s very unusual for the court of appeals not to defer to the expert agency on a technical issue like the [emission-level] extrapolation,” Sumner said during an interview with MRT. “In an appeal of this kind, most of the time the court upholds the agency, so we’re certainly delighted the court found the evidence of prejudice by the commission in the record.”

Indeed, the court ruled in favor of the FCC on the ARRL’s contention that the BPL rules would allow harmful interference to mobile amateur-radio operations. However, the FCC rule that extrapolates that emission levels decay below 30 MHz at 40 dB per decade—a figure that is accurate for single-point emission source but not for a powerline, Sumner said—was not supported adequately in the agency’s record, the court ruled.

Although the ARRL noted that Ofcom—the United Kingdom’s regulatory agency—had conducted three studies indicating that 20 dB per decade would be an accurate measure, the FCC dismissed the studies, stating that it was not a “convincing argument” but offered no explanation for its position.

“So conclusory a statement cannot substitute for a reasoned explanation, … for it provides neither assurance that the Commission considered the relevant factors nor a discernable path to which the court may defer,” Judge Judith Rogers wrote in the majority opinion.

On a procedural matter, the court called for the FCC to release all the data related to the studies upon which it based its decision. When making the ruling, the FCC redacted some portions of the studies—in some cases, individual lines of text—for the public record. Sumner said he does not know what information was not included.

“We’re certainly looking forward to seeing what it is in the commission’s study—something they haven’t shared with us but did share with the court,” Sumner said. “We’re curious to see what’s in there that led the court to conclude that the commission deliberately withheld information that was damaging to its case.”

The FCC can appeal the ruling to the full circuit court or to the Supreme Court. If it declines to appeal, the agency must revisit emission-level extrapolation issue, either providing reasoned justification for the 40 dB-per-decade factor or establish a new extrapolation factor.

If the FCC were to use the 20 dB extrapolation factor advocated by ARRL, it likely would impact the economics to deploy the technology, Sumner said.

“Presumably, the power would have to be turned down in these systems, and that might result in reduced reliability, reduced throughput and the need for more hardware to be installed—repeaters at closer intervals along the line,” Sumner said. “So we anticipate that the industry is going to strongly resist a revised extrapolation factor.”

Thus far, BPL deployments have not been a significant problem to ARRL, Sumner said. First, with less than 5000 commercial customers nationwide as of the middle of 2007, BPL is not available in many areas.

In addition, the most successful BPL technology provider—Current Communications, which has a large deployment in Texas—has worked with ARRL in an effort to ensure that its broadband rollouts do not interfere with amateur-radio operations, he said.

“We’ve had essentially no problems with Current’s deployments,” Sumner said. “We’re frankly glad that Current’s been doing considerably better in the marketplace than some of the other companies that haven’t taken the problem as seriously.”

However, if the FCC lowers the BPL emission limits, it could impact the financial side of BPL rollouts, Sumner said.

“I know [Current officials are] concerned about it, because it’s the main reason they were intervenors in the court case, on the side of the FCC,” he said.

BPL emissions also could interfere with public-safety communications operating on low-band VHF frequencies, but public safety has not expressed much concern about the matter, Sumner said.

“We’ve gotten some spotty support from public-safety communicators, but I think their main focus at this point is on 700 MHz and other higher-frequency issues,” he said. “They’re not that worried about low-band VHF, because there’s not a lot of action down there other than some legacy systems.”