Broadband Over Powerline Woes
September 19th, 2005 at 10:50am
Broadband Over Powerline (BPL) is an exciting new technology that utilises the existing powerlines to bring broadband Internet access to every home with a connection to the elctricity grid. BPL is really just a new adaption of existing Power Line Communication technology used in such things as home automation.
The alternating current that currently uses the power lines operates at 50-60 Hz depending on your location, whilst the newer BPL signals operate at around 1-30 MHz and can bring speeds of up to 2.7Mbit to homes. Whilst this is certainly a clever technology, it has certain issues.
Some people may have already worked this out simply from reading the above, but I’ll explain it anyway. Powerlines tend to be unshielded and untwisted, making them perfect antennas, and this also means that they are very good at creating radio frequency interference.
The main problem with BPL is the enourmous amount of interference that it does create, in some cases blocking out AM radio frequencies, as well as some amateur, government and defence frequencies. There have been reports of interference to the FM frequencies as well, although I find that slightly harder to believe.
Considering that virtually every suburban power line would be acting as a radio transmitter, the concerns of people in the radio industry (especially amatuer radio entusiasts) are quite understandable.
It’s not all bad news though, as the FCC and the ACMA (formerly known as the ABA) have released rules requiring “notching” of the frequencies used by BPL to avoid the interference. The majority of the BPL systems that are capable of notching frequencies operate at mainly higher frequencies and are therefore capable of higher speeds, it is expected that they will be able to provide speeds in excess of the 24Mbit potentially provided by ADSL2+
The important thing for now is making sure that the regulators are kept up to date on what interference is occuring, and to make sure that the electricity companies know that they can’t take shortcuts and create unacceptable interference.
BPL will be the way of the future, potentially providing much more than just Internet access, but it is important that it is setup in the correct manner, and the only way to ensure that is to keep a close eye on the regulators and the companies involved. I for one don’t want to lose AM radio, FM may be technologically superior, but I find AM has many benefits, including it’s incredible ability to “bounce” for incredibly long distances at night. People don’t seem to realise that AM radio is capable of stereo transmissions, or that digital radio will probably use frequencies currently used by AM radio. Certainly FM is better at reproducing music, but it is more suceptible to frequency drift.
I’m sure John B1_B5 understands the theory behind AM and FM better than I do and will hopefully be able to explain things a bit more clearly and correct any mistakes I may have made. I’ll admit that I don’t really understand the theory behind AM and FM radio very well, but I’ve done my best…
Anyway, I’m all for BPL, as long as it is implemented in a correct and cautious manner.
Samuel
Entry Filed under: IT News,Samuel's Editorials,TV/Radio/Media
12 Comments
1. John B1_B5 | September 19th, 2005 at 1:39 pm
Nothing to correct Samuel … you summed it up well ….. FM has better sound quality and is immune from electrical interference (unlike AM ). However, as you already mentioned, the tuning of FM is much more critical (as opposed to tuning in an AM station ). Briefly, with FM, the FREQUENCY of the radio transmitter is varied by the audio signal, and the amplitude of the modulated radio signal does not vary ….. with AM, the AMPLITUDE of the radio signal varies with the applied audio signal and the frequency remains constant ( although 2 ‘sidebands’ are produced ) . – So, with FM you have a varying frequency, and with AM you have a varying amplitude.
The whole story of the discovery of Frequency Modulation by Edwin Howard Armstrong in the early 1930’s makes fascinating reading. He eventually had to battle David Sarnoff (President of RCA ) and Le deForest (inventor of the TRIODE )in court for years, and eventually committed suicide in 1954 by jumping out of his New York apartment window.
He was a brilliant engineer, and as well as inventing Frequency Modulation, he also invented the superheterodyne receiver.
2. Samuel | September 19th, 2005 at 2:39 pm
For those who, like myself, are wondering what a superheterodyne receiver is, answers.com describes it as a “Radio receiver that converts all radio frequencies to a fixed intermediate frequency to maximize gain and bandwidth before demodulation.”
Wikipedia has an article on it at http://en.wikipedia.org/wiki/Superheterodyne_receiver, they also have an article on Edwin Armstrong at http://en.wikipedia.org/wiki/Edwin_Armstrong
Incidentally, his wife Marion eventually won the patent on FM radio back from RCA in 1967.
3. John B1_B5 | September 19th, 2005 at 3:03 pm
Yes, Marion did a wonderful job getting that patent back !
As for BPL … it sounds as though it has possibilities, but I won’t give it the thumbs up until I get more info on the interference problem.
4. Samuel | September 19th, 2005 at 3:28 pm
I finally found the site with BPL interference information again…
http://www.arrl.org/tis/info/HTML/plc/aud-vid.html has some audio and video recordings of the interference (if you’re wearing headphones I suggest you turn them down) and some interesting links. Most of that page relates to amateur radio, but some of it is relevant to more mainstream radio.
5. Samuel | September 20th, 2005 at 5:54 pm
Alrighty, I should probably correct a couple things as my understanding of BPL was partially incorrect at the time of posting.
It would appear that AM radio may not be wiped out by BPL, instead, it would appear that BPL interference starts just above the usual AM spectrum and continues up to the low end of the FM spectrum (which includes some analog TV services). This interferes with just about all emergency services, taxis, CB radio, remote control cars, amateur radio etc…
BPL not only interferes with these services, it is also interfered with by these services. Research has shown that BPL can be degraded and even knocked out by nearby transmissions.
The more I look at this, the less I think BPL has merit.
6. John B1_B5 | September 26th, 2005 at 3:52 pm
On the topic of interference to AM …. the thunderstorm in Canberra this afternoon (Sept 26 ) resulted in severe electrical interference to 2CC (an AM station ) , and was so bad at times, that I had to turn the radio off due to the loud ‘crashes’ emanating from the loudspeaker as a result of electrical interference from lightning .
( There was absolutely NO interference on the FM stations ) .
Does this mean I will be listening to FM more often ?
In one word … NO ! ( at least not until one of the many FM stations in the area comes up with some interesting program material ).
7. Samuel | September 26th, 2005 at 4:00 pm
The interference was audible, although not overly loud here in Central Canberra. It is still very dark outside though, and the thunder/lightening continues. The weather forecast seems to be for the rain to clear tommorow.
8. John B1_B5 | September 26th, 2005 at 4:13 pm
Well it was unbearable here in Tuggeranong …. I only heard about three quarters of your chat to our ‘mutual friend’ ( who seems to think that a large number of callers are out to ‘trick’ him ) .
9. Samuel | September 26th, 2005 at 4:28 pm
Well you didn’t miss much…if you heard three quarters of it you probably got the gist of all of it.
Anyway, in the last few minutes here in Central Canberra the interference has been producing loud “crash-zing” noises. I suspect the lightening may have been near Mitchell as the thunder was loud here, and so loud it got through the soundproofed walls of the 2CC studio in Mitchell.
10. John B1_B5 | September 26th, 2005 at 4:44 pm
Yeah …. I got the general gist of it ….. oh, by the way Samuel …. at the risk of sounding pedantic ….. there’s no ‘e’ in lightning .
11. Samuel | September 26th, 2005 at 4:51 pm
Very true…that’s a word that has bugged me for years, we just don’t get enough of it for me to ever have a reason to check.
Oh, and you’re allowed to be pedantic around here…it’s just the pesky people (tequilasunrise etc) that I get annoyed with. You’re one of the valued people John B1_B5
12. John B1_B5 | September 26th, 2005 at 4:58 pm
Thanks Samuel !