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By David Sumner, K1ZZ
ARRL Chief Executive Officer
August 1, 2005
Editor's note: Typically, only ARRL members get to read the "It Seems to Us ..." editorials that run each month in QST. We're posting this editorial that appears in the August issue of QST in the hope that both ARRL members and nonmembers might appreciate it and find it informative.
Regular readers of this page know that--to put it mildly--we are not big fans of providing broadband connectivity to consumers via the power lines. Conceptually, so-called Broadband over Power Line (BPL) technology is a step backward. Unless you intend it to radiate, putting radio frequency energy (for that's what a broadband signal is) on an unshielded, unbalanced conductor is a bad idea. Early cable television engineers weren't dummies. There were good reasons why they had to use coaxial cable in their systems, and the reasons are as valid today as they were then; the laws of physics haven't changed.
Having said that, it also must be said--as we've done many times before--that the ARRL is not opposed to BPL. We are opposed to BPL interference. If it were possible to send broadband signals down power lines without causing radio interference, we would have no objection to BPL. Indeed, we have no objection to the Corridor Systems approach, which uses the power line as a surface-wave microwave transmission line and does not fall within the FCC definition of "Access BPL."
There is no Access BPL system that is inherently free of radio interference concerns. However, on May 23 Motorola announced the first system incorporating design features that should reduce the probability of interference to radio amateurs down to a level where it is reasonable to address the remaining interference on a case-by-case basis.
There is no magic to Motorola's approach, which they call the Powerline LV Solution. It's simply better engineering.
First, they have taken the eminently sensible approach of entirely avoiding the medium-voltage (MV) lines. Other BPL schemes use the MV lines to bring the broadband signal from the fiber or wireless backhaul to the power transformer outside the customer's home; instead, Motorola uses its Canopy wireless broadband system. So, those long, un-shielded power lines that run alongside the road and through the neighborhood never enter the picture.
Second, Motorola uses HomePlug modems--which avoid all of the ham bands except 5 MHz--on the low-voltage (LV, hence the system's name) line between the transformer and the customer's home.
Third, they have added hardware filtering to provide additional protection against both egress and ingress.
And finally, if there is still interference--to shortwave broadcast reception, for example--the BPL hardware can be removed and a wireless link installed in its place.
We have not yet seen Motorola's Powerline LV system in operation. However, the ARRL technical staff was consulted during the system design and our concerns were addressed. Motorola is now working on its first test deployment and has invited amateur participation in the tests. We're looking forward to seeing and hearing (or better yet, not hearing) the results.
While Motorola is the first (and so far, the only) company to offer an Access BPL product after consulting with the ARRL, the approach being taken by Current Technologies is also worth noting. Current has avoided putting high-frequency (HF) energy on the MV lines by using low-band VHF (30-50 MHz) instead. Then, like Motorola--but without adding hardware filtering--they use HomePlug to get from the transformer to the house. So far, Current's BPL deployment in Cincinnati--which despite all the hype about Manassas appears to be the largest BPL installation in the country--has proceeded without major interference problems.
Does this mean we should quit worrying about BPL? The answer is an emphatic no!
Corridor, Motorola and Current apparently agree with us that MV lines are no place for HF energy. NTIA personnel have said the same thing--not only privately, but also in public. The HF radio spectrum is a unique natural resource that provides global communication without any infrastructure whatsoever. If we allow this precious resource to be squandered for the sake of a short-range broadband link that can easily be provided by other means, there is nothing that can replace it.
Yet, other BPL companies continue to put HF energy on the MV lines, paying little heed to the havoc that would be wrought on the HF spectrum by widespread deployment of their wares. Even worse, the FCC thus far has made no effort to separate the sheep from the goats, choosing instead to extend the existing Part 15 emission limits--intended for narrowband, short-duration emitters--arbitrarily to broadband, continuous BPL emissions. Motorola's Powerline LV announcement shows that the Commission's rules could provide the pro-tection that radio services deserve, without precluding BPL.
The FCC has one last opportunity to set things right as it considers the petitions for reconsideration of its BPL rules. The Commission's new leadership must take a fresh and unprejudiced look at the issue of BPL interference. If only they will take the time to read and understand them, the Commissioners will find that the FCC's own technical studies verify the seriousness of the problem. If they carefully review the record they will discover that their Report and Order is dead wrong in stating that "The 0 dBµV/m limit suggested by the ARRL is typically below the noise floor in the HF and low VHF bands." They will find ample justification for much more stringent limits on BPL emissions.
The previous FCC Chairman was a self-described and unapologetic cheerleader for BPL. Chairman Martin has the opportunity to demonstrate that there is more to leadership than cheerleading.
