NTIA's BPL position still a moving target

The position of the National Telecommunications and Information Administration (NTIA) with respect to BPL appears to be a moving target.

From expressing "broad concerns" about BPL in August 2003 to claiming BPL could help alleviate power line noise this past June, the NTIA now has aligned its position even more closely with that of the FCC - already an unapologetic BPL proponent. At the same time, the agency's recently amended recommendations recognize the reality of BPL's interference potential and suggest a "not-in-my-backyard" attitude toward BPL deployment near government radio systems.

In a cover letter to one of two separate filings last month, NTIA Office of Spectrum Management Associate Administrator Fredrick R. Wentland says the agency believes its "less burdensome proposals" will "adequately protect federal radio communication systems from locally generated BPL emissions while minimizing restrictions on BPL."

An agency of the US Department of Commerce, the NTIA now says it "fully supports" the FCC's proposed method to extrapolate the level of BPL emissions from power lines.
It's also dropped its call for a "height correction" for measurements below 30 MHz. Based on the NTIA's own earlier studies, the method the agency now supports could result in measurements that fail to accurately reflect actual emission levels by as much as 20 dB.

Additionally, the NTIA says it now prefers the FCC's proposal to measure BPL field strength "at various specific locations along a power line" instead of along the length of the line. "NTIA's extensive further analysis shows that the overall peak field strength that would be found in an exhaustive search along the power line would not significantly exceed the peak level measured using the streamlined approach proposed in the NPRM [Notice of Proposed Rule Making]," the agency said. In its earlier comments, however, the NTIA had advised determining field strength by tracking the entire line because its modeling demonstrated that interval measurements "may not consistently reveal the peak level of radiated emissions."

The NTIA also has reconsidered its earlier proposals to exclude certain frequency bands and geographical zones and to provide for voluntary coordination to prevent BPL interference to critical government radio systems. Since filing its comments on the BPL Notice of Proposed Rule
Making (NPRM) last June, Wentland said, the NTIA has narrowed the scope of specific bands and areas where "special protection mechanisms" regarding BPL should apply.

"Federal radio communications not specifically addressed in the proposed restrictions should be, for the most part, adequately protected in the near term by the baseline interference prevention mechanisms specified in the NPRM (eg, field strength limits, compliance measurement guidelines, and the prohibition of harmful interference)," Wentland concluded in a cover letter.

The NTIA says its revised recommendations would exclude Access BPL operation nationwide from some 2.2 percent of the HF and low-VHF spectrum and from a minuscule portion - 0.0007 percent - of the HF spectrum "in limited geographic areas." That's less than half the spectrum the NTIA
initially suggested protecting from BPL interference.

The NTIA says excluded bands primarily should be those used for safety communications "in situations where co-channel emissions from numerous BPL devices may be received via line of sight and ionospheric interfering
signal paths." Exclusion zones would include "sensitive radio astronomy sites," generally located in remote, sparsely populated areas where there would be "little or no actual constraint on Access BPL market penetration," NTIA said.

Coordination areas, the NTIA says, should apply to receivers "at known locations that must operate with very weak desired signals and where harmful interference must be prevented" beforehand with a high degree of certainty rather than "after discovery."

Prior coordination of BPL deployment using certain frequencies, the NTIA now says, should apply "in limited geographic areas wherein BPL deployment will not necessarily be constrained, depending on details of the planned BPL deployment." The NTIA also said it could no longer support a requirement for BPL systems to transmit identification codes.

The agency does not appear to have backed away from its recommendation that the FCC apply its more stringent certification, rather than verification, procedures, to authorize BPL systems that, NTIA's comments said, "pose relatively high interference risks."

The ARRL also supports certification, which would require independent testing or review of test results, as opposed to having a BPL operator merely attest that its system complies with FCC rules. The League asserts that certification offers a higher degree of confidence that deployed BPL systems will not continue to exceed Part 15 limits.

The FCC is expected to consider a Report and Order in the BPL Proceeding, ET Docket 04-37, when it meets Thursday, October 14.

For additional information, visit the "Broadband Over Power Line (BPL) and Amateur Radio" page on the ARRL Web site.

To support the League's efforts in this area, visit the ARRL's secure BPL Web site.

Source: ARRL Letter - courtesy of The American Radio Relay League

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