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EDITOR'S PAGEBPL Gives Short Shrift to Short Wave
BPL typically occupies between 5 and 25 MHz of spectrum and operates in the frequency range between 2 and 80 MHz. BPL technology has been supported by President Bush and is gaining ground commercially in the United States. In
a recent letter to FCC, ARRL called on the agency to reconsider
its rules adopted last October. According to ARRL, "FCC incorrectly
rejected the league's recommendation for a 20-dB extrapolation factor
in measuring BPL signal decay on HF based on distance from the signal's
source." "Amateur
radio uses very weak signals. Adding notched BPL noise causes
significant degradation and makes it difficult to copy weaker
signals," says Hare. "It connects using radio signals
and becomes like a giant antenna." The problem is that it is difficult—if not impossible—to completely protect short-wave signals with notching in a fully deployed BPL system. According to Hare, it takes months of fixing to remove interference even from a small, local system. It would be nearly impossible to address such interference in a system that covers an entire state. "Motorola has gone to great pains to avoid the short-wave bands," says Hare. Other companies, he says, are also heading in the right direction with the development of their systems. According to ARRL, the fact that Motorola has taken steps to mitigate the interference means that it is not unreasonable for FCC to set appropriate limits. "Short wave is the only spectrum where you can fully communicate without the help of an intermediary, like a satellite," says Hare. According to ARRL, there are currently more ham radio operators than ever. The EMC Standards Development Committee is addressing the standardization of EMC measurements of emissions from power lines. According to Don Heirman, the committee believes that these radio services should be allowed to be present, "providing that the EMC aspect of noninterference is maintained with the radio service." Heirman, vice president of standards for the EMC Society, announced these activities in the Spring 2005 EMC Society Newsletter. The EMC and Power Engineering societies have formed a joint study group to address measurements. But that may not be enough. The time to address these interference problems is now, when there are still relatively few commercial sites. FCC must keep its promise that offending systems will be required to resolve interference issues. Sherrie
Conroy, Editor
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On
a home amateur radio system you might hear birdies—a little
noise from your neighbor's computer or outside lamp post. But the
computer and the light are not emitting all the time or on all frequencies,
explains Edward F. Hare Jr., RFI laboratory manager for the Amateur
Radio Relay League (ARRL). Moving to another frequency usually solves
the problem. Broadband over power line (BPL), however, fills tens
of megahertz with birdie after birdie and uses a chunk of spectrum
that operates 24 hours a day on overhead power lines. To an amateur
radio operator, that means interference on any frequency.