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Utility Cuts Short BPL Trial
fatboy writes "The ARRL is reporting that Alliant Energy has called an early end to its broadband over power line (BPL) pilot project in Cedar Rapids, Iowa. The "evaluation system" went live March 30, and plans were for it to remain active until August or September. Alliant shut it down June 25. Ongoing, unresolved HF interference from the system to retired engineer Jim Spencer, W0SR, and other amateurs prompted the ARRL to file a complaint to the FCC on Spencer's behalf demanding it be shut down."
I live in Cedar Rapids and participated in the program. I didn't RTFA so I'm not sure what it says about this, but the mailer I got a couple days ago didn't say anything about a complaint, it just basically said Alliant had met its goals for the program ahead of schedule, and after working out a few issues there is a possibility the system may be implemented on a larger scale.
On the 0th day, God created C
I've never understood why they were so gung-ho about this stupid idea in the first place when most power grids already have multi-core fiber optic cable hidden inside the neutral wire. (they use it to communicate between substations and most of the capacity is dark - I put hundreds of miles of this stuff in the air back in the mid-nineties so I know from whence I speak) The power company already has the most valuable easements. Couple that with their existing fiber grid and they could have fiber to the curb in every major market for a lot less than the phone or cable companies who very often have to mount on existing power poles and pay $1 or more per pole for easement rights.
That's how SPRINT became a major Playa in the long distance and later, the backbone market - they used their existing easements. (for those who live in a cave, SPRINT stands for Southern Pacific Railway INTernational - your phone call 'rides the rails'...or more precisely, runs over fiber optic plowed into the roadbed of their gigantic network of railroad tracks)
Nope, it doesn't appear to have been fully rejected. Scottish Hydro Electric appear to offer the service. Website with details here:
Cheers,Scottish Hydro
Mike
Unshielded transmission line will create signals that interfere with radio service.
Not necessarily so.
Unshielded balanced feeders have been widely used ever since the introduction of RF transmission and the losses can be lower than a sheilded cable if done properly. Leakage will always be slightly higher -- but can still be extremely low providing the lines are balanced properly.
Many years ago I built a balanced unsheilded RF link that was over a mile long on a farm for a CB radio. With an input power of 500mW and a matched dummy load on the other end, the leakage from that feeder was so low as to be almost undetectable beyond a few tens of yards.
I expect that the problem the BPL trials are having is that the power circuits are not balanced at the RF frequencies (or harmonics thereof) that are being used.
Achieving and maintaining high levels of balance across the entire spectrum being used is probably going to be a *major* problem that will stand in the way of this technology.