The other shoe has finally dropped on that court decision which forced the Federal Communications Commission to delay its green light to Broadband over Power Line technology (BPL). The American Radio Relay League (ARRL), which successfully sued the FCC over its go-ahead, has obtained and published a small pile of nonredacted versions of studies that the Commission claimed supported its pro-BPL position.

The nonredacted documents, ARRL charges, offer a different assessment of the technology. For example, a redacted page (page one) from an FCC study of one BPL system's emissions rate (Main.net) concludes that it exceeded required limits, but "if distance were based on distance to the wire rather than the nearest part of the BPL system, measurements would have passed with 1 dB margin at the selected quasi-peak measurement location."

What a relief! There's only one little problem. The unredacted version of the document (page two), now made public thanks to an ARRL Freedom of Information Act request, includes a parenthesis that was whited out of the comment. So the full sentence reads (we've added the emphasis):

"if distance were based on distance to the wire rather than the nearest part of the BPL system (a suggestion made by Main.Net's CTO, but which we consider to be invalid), measurements would have passed with 1 dB margin at the selected quasi-peak measurement location."

No adversity please

It gets even weirder, but first let's review the background on this case. BPL, essentially a means of transmitting broadband along electrical current lines, was supposed to be the next big thing—a "third pipe" alternative to cable and DSL. But the market for it has been slow, and ham radio operators, led by the ARRL, charged that the service caused receiver interference.

Finally a federal court took a look at the dispute and in April of 2008 agreed that the five studies used by the FCC to back its non-interference claims were full of redaction, so to speak. The Administrative Procedures Act requires the agency to make the whole of these studies public, the US Court of Appeals for the District of Columbia ruled, not just selected portions.

Here, one judge declared, "there is little doubt that the Commission deliberately attempted to 'exclude[] from the record evidence adverse to its position'."

This month ARRL got its hands on the clean studies. Here's another example. Page one of this document measuring the field strength of a BPL system component concludes that its "Plotted field strength is 95th percentile spectral bin within emission band of specified DUT for average."

But do you see that great big blank box on the lower left of the page? That's a redacted comment. Scroll down to page two and you'll see the unredacted version of the page, which reveals the whited out text:

***NOT A POINT SOURCE***

Emissions exhibit no noticeable

decay 230 m down line from

coupler

Why would someone white this data out of a study?

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"FCC Part 15 emission limits were

developed for point sources, i.e. for emissions from a single point," ARRL Chief Executive Officer David Sumner told Ars. "A BPL

system uses wires, which of course are lines and not points and which radiate

from along the line. What the FCC staff studies showed was that BPL is not a

point source, and so the interference from a BPL device does not decay in the

same way as a point source. It decays more slowly."

Ditto for this page, which the agency completely blanked, except for the Powerpoint slide title: "Conclusions Regarding Access BPL." The unredacted version on page two says: "The tested overhead PLC devices do not act as point sources. Emission from line shows virtually no decay 230 m from coupler. Differential two-wire signal injection affects the polarization of radiated emissions from overhead devices."

On the ARRL's comparison page, Sumner says his organization has only begun to explore these papers. "We are continuing to analyze all the documents and we'll see just what has been going on," he promised.

The appeals court's procedural ruling remanded the controversy back to the FCC, which suggests that the agency could reissue its 2004 Order once it makes the relevant documents fully public. But it's unclear what the court or the FCC will do if it becomes obvious that the unredacted studies offer a meaningfully different assessment of the interference problem.

Even the ARRL is circumspect in its analysis, however, cautiously suggesting that the unredacted docs "may not support [the FCC's] own conclusions regarding BPL." How "adverse" does the evidence have to be to compel the agency to change course?

Hat tip to Broadband Reports for this story.