Conformity Magazine - December 2007 - (Page 16) national broadband strategy to benefit all Americans. Resources are better devoted elsewhere, to more promising technologies that do not pose a threat to the Commission’s radio service licensees.” Different BPL Implementations Yield Different Results The ARRL has indicated that its only concern with BPL is interference. In fact it has offered to work closely and effectively with some companies involved with BPL technology. generation-1 equipment, but when the system is operated at excessive levels, strong interference is an inevitable outcome,” he commented. “By operating this system above the Part 15 emissions limits, Ambient is making it impossible for any electric utility to use results from this experiment to reach any conclusions about the technical and commercial viability of BPL.” The FCC has called on Ambient to demonstrate its compliance with all terms of a Part 5 experimental license authorizing the system, or Figure 3: ARRL’s Ed Hare checks for interference at According to ARRL Laboratory a BPL installation in Cottonwood, AZ. face possible enforcement action. Manager Ed Hare, ARRL and (Photo courtesy of Robert Shipton.) But, in a letter to the Commission, representatives of the Current ARRL’s General Counsel Chris Group, a BPL provider, “have Imlay contended that “interference communicated regularly over the past few years. Current has has repeatedly occurred, and it has been witnessed and verified been an early leader in carefully choosing its design to avoid by a member of the Commission’s Enforcement Bureau staff. interference to Amateur Radio. They don’t operate below 30 Yet no action has been taken whatsoever to terminate this MHz on overhead lines at all, and use HomePlug technology, experimental authorization over a period of more than two and which doesn’t use the ham bands, in customers’ premises. one-half years.” To date, ARRL has no amateur radio interference reports involving Current or HomePlug equipment.” Current’s approach to BPL deployment is to limit its use of the medium-voltage lines to 30-50 MHz, and to rely on the HomePlug standard to avoid the HF ham radio bands on the low-voltage drop. Current is building out broadband networks in Cincinnati and Dallas-Fort Worth and is in talks with a number of utilities around the world. And, as noted above, a recent agreement with DirecTV will give approximately 1.8 million homes access to broadband over power lines in the next several years. On the other hand, other BPL systems have the potential to cause interference to licensed radio services. One such system that has come under scrutiny is Ambient Corporation’s BPL pilot project in Briarcliff Manor, New York. Ambient operates the Briarcliff Manor BPL pilot program under Experimental license WD2XEQ, but ARRL testing as recent as late May indicated the system was operating outside of the parameters of its FCC authorization. According to the ARRL’s Hare, tests conducted showed that Ambient “continues to operate well above the Part 15 emission limits that are stipulated as a condition of its Experimental license.” Hare said their visit to Briarcliff Manor in May marked the third time that emissions testing showed the system to be operating significantly above Part 15 emissions limits. “The spectral masks in this system intended to protect some radio services from interference work poorly enough in this 16 Conformity DeCember 2007 Ambient has responded to the FCC, indicating that they have identified an equipment failure in Briarcliff Manor that was the cause of the problems encountered. As of press time, they have removed the generation-1 equipment and replaced it with FCC certificated generation-2 technology. Hare reported that follow-up testing on the site showed that, although the upgrade was a work in progress, the partial reinstallation was no longer using the amateur bands, which were noise-free at the time of his visit. He plans another visit when the rebuild is complete. Hare also said that he and Ambient staff have been discussing ways to work together effectively to ensure that future problems are unlikely. Allen Pitts, an ARRL spokesman, says that the FCC could have taken effective action in this case years ago, offering much more timely benefit to all of the parties. BPL and Television The National Association of Broadcasters (NAB) is also concerned about BPL systems. The NAB says that BPL systems could pose serious risk of interference to television channels 2-5, especially the eleven stations currently transmitting a digital broadcast signal on those channels, as well as several stations which are likely to elect lower VHF channels at the end of the digital television transition. Thus, to ensure that the public’s free over-the-air television service remains clear of any interfering signals, NAB and MSTV strongly oppose any BPL operations in the television broadcast bands.
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