.FLYINGHEAD LETTERS TO THE EDITOR
.TITLE The ARRL on BPL
.AUTHOR Ed Hare
.SUMMARY We continue our editorial coverage of the broadband over powerline (BPL) controversy with a letter from Ed Hare, Laboratory Manager of the ARRL (American Radio Relay League). The ARRL has be the most vocal opponent we’ve seen to BPL and, in this article, we give their technical expert the opportunity to discuss the issue.
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.H1 About this series
We continue our editorial coverage of the broadband over powerline (BPL) controversy with a letter from Ed Hare, Laboratory Manager of the ARRL (American Radio Relay League). The ARRL has be the most vocal opponent we’ve seen to BPL and, in this article, we give their technical expert the opportunity to discuss the issue.
For the record, we’ve edited his submission very slightly to meet our publication guidelines. However, we’ve limited edits to punctuation and formatting for our style only. The words are all Ed’s.
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Let me chime in a bit here, if I may.
I work for ARRL, the National Association for Amateur Radio. I manage ARRL’s technical laboratory and I have been involved in ARRL’s concerns about BPL for several years now.
.TEASER To read the rest of Ed’s comments on BPL, tap here.
To get a bit outside my normal technical scope, I will first offer a personal opinion about Amateur Radio. Although Amateur Radio does have a hobby aspect, its value as a licensed radio service extends personal communications. Just as an example of the many ways that Amateur Radio makes important contributions to the public good, see "The Value of the Amateur Radio Service" (at http://p1k.arrl.org/~ehare/bpl/emcomm.html).
You will find a more polished presentation in the information at the ARRL Public Relations Department (at http://www.arrl.org/pio).
If this issue were only about Amateur Radio, and BPL were the only way that broadband could be delivered, I think that the issue would be easy to decide. However, the spectrum that BPL uses covers 2 to 80 MHz, a range that encompasses not only Amateur Radio, but CB, international shortwave broadcasting, and a host of government and commercial users.
The upper end of that range also extends into public-safety communications between 30 and 50 MHz, used by a number of police, fire and ambulances, to name a few. Although some of that operation is migrating to other spectrum, in some cases, the choice to use 30-50 MHz is intentional, as it allows the best coverage in hilly terrain. Above 54 MHz, BPL can use frequencies allocated to television broadcasting.
One need to look no farther than the video and audio recordings of BPL interference to see that if not done correctly, BPL has a significant local interference potential, as shown in the video at http://www.arrl.org/tis/info/HTML/plc/aud-vid.html.
The range between 2 and 30 MHz is unique, in that it is the only spectrum that allows stations separated by thousands of miles to communicate with each other without the need for intervening technology (i.e., wires, fiber, repeaters or satellites).
BPL is far from the only way to deliver broadband to end users. Each of the following are mainstream broadbands technologies serving hundreds of thousands — or millions — of users today:
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.BULLET Cable
.BULLET DSL
.BULLET Commercial licensed wireless
.BULLET Commericial unlicensed wireless
.BULLET Wi-Fi community networks
.BULLET Cellular telephone
.BULLET Satellite
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In most cases, BPL is far from the "best" way to deliver broadband. It needs repeaters installed on the medium-voltage distribution lines every 2000 feet or less. Those lines were not designed to carry broadband signals. To the contrary, they were designed to carry 60 Hz AC [alternating current] power and are a pretty poor conductor at radio frequencies. It is a noisy environment, and leakage from those overhead wires is assured, as it ingress — the leakage of licensed services’ transmitters into the wires. One has to note that if coaxial cable and Category 5 (or higher) wiring weren’t needed to carry broadband signals reliably, they would never have been invented.
I attended a presentation given by Ron Hranac, a member of the Society of Cable Communications Engineers Board of Directors. Hranac outlined the improvements that need to be made to a well-maintained cable plant to make it work reliabily for broadband use. Things like the phase characteristics and gain flatness of the system need to be closely controlled. The idea that all that really isn’t needed, and that one can just put those signals onto any old wire, is not technically supportable. See "Deploying VOIP on the outside plant" (at http://p1k.arrl.org/~ehare/ARRL_EMC_Committee/Deploying_VoIP_on_the_Outside_Plant_files/frame.htm and BPL Presentations (at http://www.arrl.org/tis/info/HTML/plc/presentations.html).
There is no doubt at all that BPL can and does cause interference locally on any spectrum it uses, if that spectrum is in use locally. In residential neighborhoods, this includes Amateur Radio, CB and the reception of international broadcast. Some BPL manufacturers have made progress at filtering their equipment well enough to avoid interference to Amateur Radio, although some have not. The BPL operator in Manassas, VA, for example, has been embroiled in an interference battle for over a year. The FCC recently had to require that BPL operator to report how it would notify its customers in the event that the FCC ordered it to shut down.
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BPL is not without its uses, and other than the interference issues, ARRL is not opposed to BPL deployment. To the contrary, we have a BPL system test operating here at ARRL HQ, in full cooperation with Motorola, the BPL manufacturer. But for BPL to live up to its potential, it must address its interference problems head on, and live within the limitations of a noisy environment using wires not ideally suited to the task. So far, some companies have made progress with the former. The latter is being addressed through the use of repeaters and amplifiers located at intervals much closer to gether than other technologies using better-suited wiring need to use.
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.H1 Product availability and resources
To read "The Value of the Amateur Radio Service", visit http://p1k.arrl.org/~ehare/bpl/emcomm.html.
For more information on the ARRL Public Relations Department, visit http://www.arrl.org/pio.
For a BPL interference video, visit http://www.arrl.org/tis/info/HTML/plc/aud-vid.html.
To read "Deploying VOIP on the outside plant", visit http://p1k.arrl.org/~ehare/ARRL_EMC_Committee/Deploying_VoIP_on_the_Outside_Plant_files/frame.htm.
For more ARRL BPL presentations, visit http://www.arrl.org/tis/info/HTML/plc/presentations.html.
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.BIO Ed Hare, W1RFI, is the ARRL Laboratory Manager. He is a member of the ASC C63 EMC Committee and chairman of Subcommittee 5, Immunity and Ad hoc BPL Working Group. He is also a member of the IEEE P1775 BPL EMC Committee, IEEE, Standards Association, Electromagnetic Compatibility Society, and IEEE SCC-28 RF Safety. He is a member of the IEEE EMC Society Standards Development Committee and chairman of the BPL Study Project. He is also a member of the Society of Automotive Engineers EMC/EMR Committee and is on the Board of Directors of QRP Amateur Radio Club International. ARRL’s general information on BPL is available from http://www.arrl.org/bpl.
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