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Broadband via Power Cables trials in Scotland
Wacko writes "Scottish Hydro-Electric have started a trial of Broadband internet access via power lines. Just plug the modem into any power point in your house, with no need for additional lines into the house, and reasonably priced too. Details are a bit scketchy right now but interesting to see how the trial goes."
The contractor bringing this to homes in North America is Current Technologies. They have a demo home set up with Pepco and will be doing customer trials this year.
Competition == Good.
Apologies to all those folks in rural America, but they're still screwed. Actually, this technology would be much more difficult to implement in the United States and Canada than in Europe.
The U.S. power grid typically delivers moderately high voltage to each little neighbourhood--a small handful of homes at most. At that point, there is a small transformer (a "pole pig"--no ethnic slur intended) for the last step down to 110 volts.
European grids usually step down to 220 volts, and do it further from the homes. There are significantly fewer transformers per capita, as each transformer serves more homes.
The problem is this. The high frequency data signal gets flattened out going through a transformer--those big coils act as a low pass filter that eats your data. You have to pick up the signal from the server before the high voltage side of the transformer and reintroduce it on the low voltage side (and do the same thing in the other direction for upstream signals).
In Europe this is not an insurmountable problem: you just need to hop over a few transformers in a handful of central locations. In the U.S., you have to install some sensitive electronics on every pole pig--exposed to the elements in a lot of widely separated, awkward to service locations.
Oh, and rural America has it even worse--some homes have their very own transformer, and would need their very own jumper for signals. Also, if there is a long enough length of power line back to the substation, the inductance of the power line will be enough to eat any high-bandwidth signal.
~Idarubicin
The biggest problem is getting the signal through the pole pigs (can-type transformers on top of the hydro poles) -- they are big iron monstrosities that don't pass much past 1kHz or so due to their design.
One method which can be used is to simply wire some high voltage capacitors across the primary and secondary of the transformer -- they'll conduct at high frequencies (you tune this) and voila -- your signal jumps the transformer.
Of course, the problem with that is you're no longer isolated from the street-line voltages -- anywhere from about 6.9kV to 44kV, depending on who else is in your neighbourhood. The "right" way to do it is to have a line-powered conveter box at each pole pig which jumps the transformer optically, but that's expensive.
I've always been a fan of power line transmission. There's one in particular I was always amused by (no link handy) -- they claimed that by using a maser they could modulate the magnetic field without altering the voltage and current. I wonder what they think of Maxwell.