[TriLUG] Powerline - Ethernet over AC lines & Linux
jbrigman at nc.rr.com
Sat Sep 22 01:24:45 EDT 2007
On Fri, 2007-09-21 at 21:55 -0400, Ron Joffe wrote:
> On Friday 21 September 2007 21:39, Neil L. Little wrote:
> > Of course there is
> > more to the story but basically BPL is a bad idea.
> Sorry to be the dissenting view here, but it's not as much that BPL is a bad
> idea, but that there have been some bad implementations. If you were a rural
> farmer and wanted something faster then dial up, in many parts of the country
> you don't have much choice. If your local electric utility comes and offers
> you a choice, at what cost would you take it?
What do you mean by separating the idea of BPL from implementation? Can
you cite any source quantifying demand for BPL?
How can you say the farmer has no choice when HughesNet is available to
anyone with an unobstructed south-southwest view? What about the current
crop of cellphones (ie: Blackjack) which can function as a computer
modem for the new 3G cell-based broadband network?
The one person I have ever known who didn't have a broadband media
internet alternative successfully used the Sprint network for RF
networking. BPL was no more a reality for him than it would have been
for your mythical farmer.
> Powerline carrier in itself works quite well, Many utility have (or are in the
> process of) implementing powerline carriers to read their electric meters.
> That's a situation where the technology is there, it does not interfere, and
> provides a very good solution. The situation comes when you try to increase
> the bandwidth to the point where the electric lines start radiating a
> significant amount, then you get nice radio spectrum interference.
Power line carrier does not work well and is not used to read electric
meters. Please substantiate your claims by citing your sources.
Your own meter is not remotely read via power line carrier. If it is
remotely read, it's via an RF system. Most successful residential meter
reading systems communicate in the RF spectrum and are read from a
central point or by a human in a truck. The meters in my neighborhood
are read via RF. Progress Energy reads meters this way:
What does "works quite well" mean? Does less than 5 miles of usable
transmission line with repeaters every 2000 feet mean "works quite
Are you aware that at least one currently-available BPL system is an
extreme bandwidth hog because the repeaters have to use separate chunks
of the RF spectrum to read from one section to the next?
Are you aware that BPL runs on frequencies already in use by Amateur
Radio, Public Service agencies and even FM radio and Television?
Are you aware that BPL power levels are equivalent to that used in Ham
Radio "QRP" devices, which can radiate around the world?
Are you confusing BPL with X-10 devices?
BPL does not promise the ability to plug into a bedroom power outlet and
download your favorite pr0n.
The only viable lengths of power line to use are the points where the
distribution lines branch off the higher-voltage transmission lines at
the substation. Then at the curbside, they pull the signal off the line
and route it to the house via other means. Progress Energy does not feed
BPL directly to the house because the final step-down power transformer
(the gray can on the pole or green box at the property line) cannot pass
BPL signals in any usable manner.
As far as hams are concerned, BPL does not work well because power lines
are excellent antennas in the frequency ranges used by BPL:
> The power levels are a direct result of cost to benefit ratios. Some system
> utilize rather low power, and many repeaters to achieve a BPL solution which
> does not interfere. Repeaters are expensive to install and maintain. So there
> are clean solutions, but at a higher cost. Finally it comes down to what the
> farmer in the rural area is willing (and able) to bear to catch up to the
> rest of us.
What cost benefit ratio determines BPL power levels? Can you explain
what you mean by this?
Please substantiate your claims of zero interference by citing your
sources, preferably sources describing implemented BPL systems, not BPL-
provider-propaganda. (which rules out anything published by George
Spencer on the topic...)
All BPL systems interfere, regardless of power level. The question is
only "How Much?" The problem with BPL is that it would generate
BPL differs from any other available internet supplying medium in that
it is the first medium that specifically, expressly interferes with
other radio services. NO OTHER MEDIUM has this disadvantage, not even 3G
Your farmer still has no bearing on your argument. He's probably surfing
the 'net on an optical fiber line hosted on power poles or the power
right-of-way, if he's not using satellite.
It is this writer's sincere hope that the life will be crushed out of
BPL by all other physical media alternatives.
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