Utility Cuts Short BPL Trial 239
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."
RF interference. (Score:4, Informative)
I wonder why someone thaught it would be different in the US, even with its more stringent laws about RF interference.
Do these people not do basic searches on prior work?
Re:consumer versions (Score:2, Informative)
The problem is that Power lines tend to be very noisy which means you have to put more power in to make your signal discernable at a distance, or your signal will be swamped by the noise.
In a perfect world you could add an extra High frequency signal to the power signal which could easilly be filtered out, but in the real world this is complicated by noise from Electric motors, high frequency Electronics such as computers and mobile phones and the environment in general such as Storms. You also have to either up the signal in combination with the distance or add more expensive repeaters at decreasing intervals. The stronger the signal, the more leakage on RF frequencies.
Comment removed (Score:1, Informative)
Re:The ARRL - we're here to help. (Score:5, Informative)
Re:consumer versions (Score:4, Informative)
You mean powerline ethernet? Sure...
From my perspective (Score:5, Informative)
Re:consumer versions (Score:2, Informative)
It's actually the load of that electrical device lowering the impedance on the electrical circuit on 'house-side' of your meter box. The low impedance inhibits the propigation of the high-frequency signal (the one the intercom uses).
So the intercom signal is drowned, but from low impedance, rather than additional high-frequency RF (noise).
They already have fiber (Score:5, Informative)
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)
Re:From my perspective (Score:1, Informative)
For all you little PRO-BPL'ers (Score:0, Informative)
FUCK BPL
Re:The ARRL - we're here to help. (Score:1, Informative)
Not rejected - available in part of UK. (Score:5, Informative)
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 [hydro.co.uk]
Mike
Re:As a UK radio ham (Score:1, Informative)
Re:As a UK radio ham (Score:5, Informative)
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.
Re:They already have fiber (Score:2, Informative)
Re:Hams should help solve a problem, not create th (Score:5, Informative)
If you had done even a modicum of research into this, you would know that what the ARRL and others are complaining about is BPL or PLC in europe that uses the HF spectrum for transmission. Over long unshielded agind powerlines, this == big fscking antenna. Hence the bleed, and RF issues ensue.
They have also stated (the ARRL and others) repeatedly that they have no problem with BPL itself. They have problems with the power companies that are trying to roll this out to make an extra buck or two. I mean, lets face it, many power companies have problems just keeping the power going, let alone BPL... and to have to handle interference complaints as well?
But in any case, the people who are against BPL, as I said, are against the version that uses the HF spectrum. Not just parts of the HF spectrum, but the ENTIRE HF spectrum from around 3 to 30+MHz. They support other means readily, such as the BPL system that was being developed in the desert that used gigahertz transmission frequencies instead of HF freqs... or the aforementioned fiber wound around the power lines, and some companies ALREADY have cable wound around the powerlines that they use themselves.
Re:As a UK radio ham (Score:1, Informative)
Re:As a UK radio ham (Score:1, Informative)
BPL, on the other hand, is not a traditional "transmission" line at any frequency beyond 60 Hz and even has substantial radiation at those low frequencies. It's a disaster for anything else that uses electromagnetic free-space waves (radio, TV, hams, cell phones, et.al.).
What drugs were these guys on, anyway?
Ham radio - not just a hobby (Score:3, Informative)
I honestly don't think the general public has a clue about how much amateur radio operators do beyond being just a hobby. They're mentioned in news reports all the time, but people don't understand it, so they just ignore it.
For example, recently we got hit by a few tornadoes, so I popped some batteries in an HT my dad gave me, headed for the basement, and flipped on a local repeater to listen to the weather spotters. As the reports of hail and tornado locations came in, my neighbors commented that they always wondered where those reports came from.
Every natural disaster I can think of has had news reports of how essential the hams have been.. everything from Hurricane Andrew to 9/11. Heck, hams even help with communications in things as minor as parades and marathons. And they train annually to ensure that they can operate without any infrastructure. I've seen some interesting setups to get away from relying on gas powered generators.
Personally, these are people that I'd like to keep happy.. because when the shit hits the fan, they're our most reliable communications.
Re:As a UK radio ham (Score:3, Informative)
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.
As someone with a little common sense I find your assessment of the BPL situation based upon your little project immensely stupid for several reasons. They are as follows:
1. Broadband over power lines is being considered for only one reason. Virtually everyone in the US has electric power delivered to their homes. Typical types of high speed internet service such as DSL or cable has no where near the coverage area as that possessed by electric power lines. Therefore BPL would offer a means to offer high speed Internet services to everyone. However by its very definition broadband internet results in a signal that occupies a large part of the electro magnetic spectrum.
2. Power companies readily admit that their power lines are unshielded transmission lines. There is no way to prevent an unsheilded transmission line from radiating energy at various frequencies and their harmonics. Unshielded transmission lines are known by another name, antennas.
3. I don't know about where you live but in the average community here in the US has these things called STREETS. These streets occur at intervals of about 30 to 50 yards. These streets are typically layed out along north/south and east/west lines. As a result of this pattern we in the US have blocks between the streets which is where we tend to build our houses. Because of this layout even unshielded balanced feeders would radiate enough energy to cause interference to every home in the country, effectively shutting down not only the amatuer service, but also commecrial AM, aeronautical radionavigation and communication, maritime communication, as well as governmental communications systems.
4. You ignore the fact that every house has a feed off of the power system, as well as the electric wiring WITHIN the home. This brings an antenna radiating an interfering signal within the home.
5. You ignore the fact that most permanent ham shacks get their electricity from the electrical wiring of the home. This, according to you, brings a signal that is "almost undetectable beyond a few tens of yards" to within INCHES of the equipment being interfered.
6. According to FCC rules any entity producing interference to licensed radio services is required to eliminated the source of interference. If the interference can not be eliminated, the source must be shut down. Amatuer radio is a licensed radio service, since every operator must be licensed by the FCC before going on the air.
I hope you can see that there is no easy solution to providing interference free BPL. I hope that the FCC will see this for what it is, the electric utility companies attempting a power grab for control of internet access in the US, to hell with all else.
Tim Worrell
W2TKW
theory vs practice (Score:5, Informative)
It ain't like that in practice.
Imagine a drainpipe stuffed with tennis balls. When you try to push in an extra tennis ball, what happens is that all the other tennis balls give a little, and for one fleeting instant there really is an extra ball in the pipe. Then the balls expand back to normal size and one is shoved out the far end.
Now, any pair of wires will have a capacitance (since they are conductors separated by an insulator), an inductance (since they are wires; at low frequencies you need a full-on coil to get any effect, but at high frequencies any slight bend will do the job) and a resistance (since they aren't perfect conductors). It's what electrical engineers call a composite impedance, and what everybody else calls
For any given transmission line, if you stick a battery across the terminals at one end and a resistor across the terminals at the other end, look at each end with an oscilloscope and have some magical way of lining up the time axes, you won't see just a simple step change of voltage. When you apply the battery to the T.L., it looks like some composite impedance (which it is) and likely draws more current than the resistive load at the far end wants, since it's charging up the capacitance of the line -- or less than that, since it's charging through an inductance. One or the other phenomenon will win out every time.
Once the capacitance of the line has charged -- via the inductance and resistance of the line -- it then begins discharging into the resistor on the far end. Actually, it doesn't wait at all, but starts discharging as soon as it has begun charging. And what you may even see, is a pulse of current reflected back towards the battery, if too much current went in at first compared to what the resistor was expecting. You can even get multiple reflections if the first one isn't exactly right. What you essentially see on the scope traces is a damped sine wave at the frequency at which the resistance and capacitance of the line resonate -- and a delay between applying power from the source and seeing it at the load.
That's what you get with DC. With AC, the capacitance and inductance tend to distort the shape of the waveform, but not change the frequency -- though it's very likely that other frequencies will be added in. Also, anything under a few hundred kHz behaves mostly like DC -- albeit more-or-less-slowly-changing DC -- but broadband networks need carrier frequencies measured in MHz, and by the timed you get to that sort of frequency, the AC phenomena are well established.
Now if all you are concerned about is getting the maximum energy throughput, as are the electricity board for example, then you want to minimise resistance (which turns energy into heat -- capacitance and inductance just store it in electric and magnetic fields, respectively, then give it up again) even if that makes the line highly capacitive or inductive. All that will happen is that you'll get a huge reflection the first time you connect up, then a series of ever-decreasing ones, but most of the power from your source ends up in the load even if it takes awhile to make it down the line, and even if the shape of the waveform is significantly altered.
If you want a transmission line that does not
Why does BPL to use HF spectrum? (Score:2, Informative)
I do not understand why BPL has to exist in conlict with HF. Broadband is essentially a big fat RF channel. It could be made to work at much higher frequencies that will not bounce off the ionosphere and turn the HF spectrum into a global RF septic tank. If it was done properly, they could probably get more bandwidth (and therefore higher speeds) by using higher frequencies.
One of the other posts commented on the viability of wrapping fiber optic cable around the power lines. I like that idea best of all. No RF problem, OC-3 speed, what's not to like?
All UN member countries are subject to the ITU... (Score:2, Informative)
Re:Why does BPL to use HF spectrum? (Score:3, Informative)
So the use of RF on these lines is limited to a couple of MHz, you cannot carry things like WiFi (2400 MHz) over powerlines.
Of course the use of low frequencies also limits the bitrate. As it is also shared between subscribers on the same power segment, the bitrate per subscriber is not very attractive.
Use of power lines for broadband should be abandoned. More suitable lines should be used. Even telephone lines are more suitable (also because there are separate lines to each subscriber).
Or else, more suitable lines (like fiber) should be put in place.
Re:Why am I totally unsurprised? (Score:3, Informative)
It's nothing like the phone system. The phone system is much lower current (and radiation is therefore proportionally less). It uses twisted pair, which cancels the magnetic field of the signal in the wire, reducing radiation even further. And it is commonly buried underground, where the moist soil acts like conductive shielding, instead of being strung high in the air on poles.
And the signal isn't even analog the entire way -- do you think the telephone companies still send analog signals all over the place? Once the signal is in the digital domain, it can be sent over fiber optics, which do not interfere with anything.
Yes, DSL works. Because it's absolutely nothing like BPL, which is a harebrained monstrosity.