Broadband over powerlines?

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jerryb52

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Lake Worth, Florida
I heard that the power company has been approved for broadband internet connections.
Does anyone know how that could work?
I don't see how a signal could be sent through the same lines as power???

Thanks :confused:
 
Re: Broadband over powerlines?

You are correct. How can more than one radio signal be sent through the air at the same time? The principal is the same as signals in the air or through space. It is an over simplification but it works. :D
 
Re: Broadband over powerlines?

Actually it is nothing new at all. POCO's have been sending single side band RF signals down transmission lines for decades called telemetry. Look at and 138, 345, or 750 KV substations and look up closely at the line and you will see huge chokes called traps where they enter and leave the yard. These traps are the points where the RF signal is injected and received. The traps look like a huge coil about the size of a wine barrel.

It is actually a very simple process. Since the line frequency is 60 Hz and the carrier frequency is much higher, it is very easy to separate the two. The traps are very low impedance to 60 Hz power line frequency and allow 60 Hz power frequencies to pass, but they have extremely high impedance to RF frequencies and block the RF signal. This allows the two frequencies to be separated from each other. From there all you have to do is couple a RF transmitter to the load side of the trap through a high voltage capacitor. The value of the capacitor is chosen so that it completely blocks the 60 Hz power and passes the higher RF signal frequency.

The same principle can be used for consumer data use. Since the line voltage and currents are much lower the system can be made to fit into a small box at or ahead of the meter. This black box would then need a coax or a pair of signal conducts going to a modem for the customer use.

The only problem I can see is one of security. It seems it would be a simple matter of parking under any power line with a RF reciever and intercepting the signal. It would take special equipment to intercept, but I am sure someone or commercial equipment would be made to do it.


Edited for spelling errors and clarity.

[ October 15, 2004, 09:48 AM: Message edited by: dereckbc ]
 
Re: Broadband over powerlines?

There has been some concern voiced by ham and other radio operators based on the possibility of radio frequency interference radiating from the power lines.
Don
 
Re: Broadband over powerlines?

The simplest filter provides 6db per octave seperation. That means at just 1 megahertz the signal seperation from 60 hertz is better than 84 db. I'm looking at one of my DSL filters used for my phone line and, without transcribing the whole thing to schematic, it looks like a second order filter. Those do 12 db per octave and would put the signal seperation at 168 db. The components needed for this are small and cheap. A 4th order filter could be used, very inexpensively, that would make the signal seperation 336 db. That would put the 60 hertz "noise" in the realm of cosmic radiation. And that's if the data frequency is only 1 megacycle.

I say the POCO may have done some of the math already.
 
Re: Broadband over powerlines?

I know of utilities that have installed fiber optic cable in the overhead shield wire on transmission lines. This method would enable them to carry miltiple signals at one time.
 
Re: Broadband over powerlines?

Don, HAM operators are concerned about being bothered by interference? That's got to be the very hight of hypocracy.
 
Re: Broadband over powerlines?

Ughh, this again? Short answer is yes it has been done for years but it is never going anyplace for broadband Internet.
Click to expand...
Hal, broadband service is being offered in Cincinnati by the local electric utility. We are sending some engineers there to look at their system to see if we want to get into broadbanding ourselves. :D
 
Re: Broadband over powerlines?

The only problem I can see is one of security. It seems it would be a simple matter of parking under any power line with a RF receiver and intercepting the signal. It would take special equipment to intercept, but I am sure someone or commercial equipment would be made to do it.
Click to expand...
Dereck with cable broadband we have the same set up the internet single is a high frequency carrier signal (@700mhz down around 300mhz up) that is modulated with the digital info imposed into the cable TV cable. this is called a node and each node can control which I.P. address are allowed to receive connection. if this wasn't possible then anyone could steal internet service by just having a cable connection. The same theory apples to power lines with the exception of a few added components to deal with the H.V. and the 60hz.
 
Re: Broadband over powerlines?

The reason I said what I did was because there were threads on this subject at least a year ago. I don't remember if it was in this forum but the discussion and links pretty much showed that where the service was being offered was actually only a beta test in some european country and under consideration here. The biggest roadblock was radiation from the unshielded wiring both inside and outside of the building. It was not just amateur radio operators that were concerned but the FCC also.

Cable companies have to comply with strict requirements to offset frequencies and limit their radiation- and their system is fiber and shielded coax. The reason is that CATV systems carry frequencies (from below 50Mhz up to 1000Mhz) which over the air are used by many, many services, some critical such as aircraft navigation. There have been actual cases where an aircraft's navigation system locked onto a leaking CATV signal rather than the proper transmitter. This is why it is so critical that CATV signals be confined to their plant and not allowed to leak. (Side note- this is why we need to install CATV coax with the correct connectors properly installed.)

The same radiation problem is inherent with powerline broadband only at a much greater magnitude. There is no shielding to begin with so there is no way to even control it.

This is why I say do we really need yet another way to provide broadband internet if we are going to have to deal with this kind of problem?

-Hal

[ October 15, 2004, 11:37 PM: Message edited by: hbiss ]
 
Re: Broadband over powerlines?

I have read about this but I personally don't see it going anywhere fast for practical reasons. Sending delicate modulated data over power lines is like listening to a symphony with headphones at a rock concert, also how are signals sent around xfmr's?? Maybe some have this figured out but I think there are too many issues to deal with when wireless city nodes are much more praticle.

My 2 cents..
 
Re: Broadband over powerlines?

We did some testing and decided the problems were too great. The devices to go around transformers worked fine but we were too skeptical about the whole system (like most of you). Our management has now told us to look into this again since it is successful. Trust me, I understand your concerns. :D
 
Re: Broadband over powerlines?

I would like to see the technical standards the FCC adopted, particularly relating to radiation. Those links on the UPLC page go around in circles... wonder if that means anything? :D

-Hal
 
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