Slashdot Mirror
AM Frequency Hinders ADSL Capacity
hajmola writes "a recent study has shown that AM radio may be causing problems for ADSL. According to this story at Network World, interference from AM stations can slash high-speed bandwidth by 40% on approximately 15% of ADSL connections. While AM interferes with download speeds, it does not affect upload speeds. AM frequency only affects ADSL and its subsets (not SDSL), including rate adaptive DSL and G.lite. "
That sure sucks. Told ya they should have shielded those lines.
http://come.to/twistedgreen
well, it's time to decide what's really important here. go with the bandwith. ditch the am.
When you start with something like 1.5 Mbit/s download, a 40% drop in speed should not make service infeasible. It is a good thing that the upload speed is not affect as it begins lower(?)
I wonder how this will affect AOL's strategy to push the ADSL technology as opposed to bust into the closed cable rings.
Please visit FreeDonation.com - You can donate Food and Medicine for FREE to Save Children (You can donate once EVERY DAY). The donation is fully paid by corporate sponsors with the money they would have spent anyway on advertising. There is no charge to you.
Please visit http://www.freedonation.com and save a life for free every day!
Damn...I don't know what to give up: ...
My ADSL, or my AM transmitter on which I welcome our leaders from space
Regardless, we will all be dead in a month anyways...we all know that 'ping' is not Y2K compliant and therefore, moron sysadmins will believe the 'net has crashed and thus we will witness the biginning of the end.
-Davidu
# Hack the planet, it's important.
So how do we know ADSL doesn't interfere with AM radio? For the love of god, this damned technology could be what's keeping me from my broadcasts of "the joy of cooking" on NPR!. Oh the humanity!
People are finally figuring out they should have their phonelines SHIELDED! what a concept! :-)
:-)
(I've got my phones running through CAT5 now and have never had better connect speeds)
I guess the problem now is what to get rid of - AM radio or ADSL? let's see - AM Radio... gives us - talk radio and spanish stations over really bad mono audio. ADSL gives us nice bandwidth, neat lookin router thingies (I like the little cisco/netspeed router thingy), and more bandwidth.
--onyx--
Wouldn't this mean that both phone lines and AM radio stations are in violation of part 15 of the FCC rules? The AM radio stations are guilty of causing harmful interference, and the phone companies are guilty of not accepting interference gracefully.
-Rigel
I have ADSL and a radio..The radio is near the ADSL modem thing. I turned on the radio and it didn't work... till I hooked up an AM antena.. Then it seemed to work fine.
My DSL seems to work great (as advertised) except when Bell-Atl removes my dial tone for no apparent reason as they've done from time time (Just to keep me on my toes?) .
The fact that I'm really close to the CO might have something to do with it.
I don't know about other people, but I live right next to the telco switch basically, and I get the speed as advertised ( 1.5mbit/128K ). Can't wait untill 5 years time when we'll be able to put to use all that fiber pacbell is laying around here. Ofcourse I probably won't live here then... and I might have to deal with bellsouth which I would not look forward to at all.
rm -rf ~/.signature
I have Bellsouth's ADSL service and I have had a fine experience. Nearly 1.5 mbps download, not that many outages, etc.
So thanks to the guy giving play-by-play of the local junior high football game in panish on AM560, I lose somewhere near 2MBps? I'd sacrifice the bandwidth only if people would play decent crap on the radio...
The ABSTRUSE One
Jason Byrons
"You all laugh at me because I'm different
I laugh at you because you're a
So if AM interferes with ADSL, and high voltage power lines interfere with AM, does that mean Slashdot will load faster if I live under high voltage power lines? Or does that just mean I'd get brain damage while reading Slashdot?
Damn, sometimes it's hard to pick the lesser of two evils...
many light dimmers will hash out your am radio when you turn them on, plus they can go all the way up to 3 MHz. This really should not be a suprise, as telephone wires are essentially longwire antennas.
ASDL. Sounds nice. Heard a lot about it. But there's one little problem: I live in the netherlands. Ofcourse, our government claims that we are one of the leading countries on the digital highway (NOT!), but new technologies like ASDL are outdated before they are implemented here. I know of one company that's currently providing ASDL-internet-access, but it's only a pilot program, for 300 lucky inhabitants of Rotterdam. I (i live near Utrecht) have to wait a couple of years, I think.....
--
If code was hard to write, it should be hard to read
I bet adsl would really suck in venezuela w/ over 180 AM radio stations. Oh wait, what wouldnt suck w/ that many AM stations and little/no fm.
I happened to attend a talk last week by Professor Cioffi of Stanford University, the inventor of the DMT technique widely used in ADSL. The issue of AM interference with ADSL transmission came up during his presentation. However, what DMT does is to optimize the transmission by reducing the strength of the signal sent on frequency bands where the noise is high (or where FCC regulations do not permit transmission due to emissions produced by the DSL line), and increase the signal strength on bands where the noise is low. If I recall correctly, AM interference is accounted for and the actual ADSL specs do not transmit a significant amount of energy in the AM frequency bands, so it's strange that this article identifies AM interference as a problem.
It's about time AM left the air. Besides perhaps a little bit of nostaglia and an unexpired radio band license, I don't think there is a single technical advantage. I think the list of disadvantages go on and on .. poor spectral efficiency, wasted carrier energy, high sensitivity to noise, poor sound quality ...
Wait a minute, I thought certain frequencies were reserved, and AM radio happened to be one of them. So why now is this being noted? You would imagine that, sitting in a lab Engineer Bob would think, "Hey, this frequency is between 400-1400KHz, I wonder what else is in that frequecy range".
- notes/node4.html#equNyquistShannon
Actually, wait another minute. How can you pipe 1.5Mb/s over AM frequencies, anyways? Don't you need 2x frequecy to send x b/s? Doesn't Nyquist theorem state this?
Ah, here it is:
"The Nyquist-Shannon Theorem states that an analogue signal of bandwidth B can be completely recreated from its sampled form provided it is sampled at a rate s equal to at least twice its bandwidth."
Found at: (no, I am not going to piss around with HTML tags)
http://www-dept.cs.ucl.ac.uk/staff/S.Bhatti/D51
Sorry, just a bit of communication theory from a sleep derprived engineer-in-training.
"Don't mind me cutting myself on Occam's Razor"
I remember this mention in a study done by avalon.net two years ago. This piece gives some more detail regarding frequencies at cross purposes.
As it mentions, a T-1 loop running in parallel to your POTS pair can also cause drop-out in your DSL frequency spectrum.
Call on God, but row AWAY from the rocks!
You mean those big numbers underneath the real station numbers on my clock radio actually do something?
I say knock off DSL. In no more than two years this country will have more dsl consumers than AM radio listeners. Of course I may be way out of touch. Lets get a petition going and send it to the FCC. Digital sigs count now!
I say knock off AM radio. In no more than two years this country will have more dsl consumers than AM radio listeners. Of course I may be way out of touch. Lets get a petition going and send it to the FCC. Digital sigs count now!
AM Radio is great! Its signals bounce off the atmosphere allowing stations to broadcast incredible distances. At night, AM stations on the west coast of the US can be heard up and down the coast, east to the Rockies and by all the ships in the Pacific. That compares to the paultry few miles DSL works before slowing down.
Sig goes here
This could be an interesting opportunity for some daring developer. How about this for an idea: The ADSL modems characterize the link and determine what frequencies they're receiving interference on. They use this information to control a separate AM tuner to discover if the interference is due to an AM station. If it is, they use the demodulated AM signal as an input to a noise filter to reduce the AM signal's power in the data transmission, and voila! You've nearly perfectly cancelled out at least one source of heartache.
Thoughts from the peanut gallery?
--Joe--
Program Intellivision!
-A.P.
--
"One World, one Web, one Program" - Microsoft promotional ad
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
Nor Tony Orlando
One thing that often gets missed in this discussion is that amateur (ham) radio is also degraded by ADSL.
Two prime frequency bands: 75/80 meters in the 1.8-2.0 Mhz range, and 40 meters in the 3.5-4.0 Mhz range. In both cases, the amateur radio operator is often trying to receive a signal from a 100 watt (typical) transmitter in a foreign country. The ADSL 'white noise' overpowers the signal.
Amateur radio shares many traits with open source software. Cooperation and sharing of information are respected qualities in an operator. A non-trivial number of hams still build their own equipment or modify the design to improve performance.
I think ADSL is pretty cool, and wish both of my hobbies could co-exist.
Rick Evans, KG4FER
Orlando, FL
- A.P.
--
"One World, one Web, one Program" - Microsoft promotional ad
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
So does this cause packets to be dropped/corrupted, or does it interfere in some other way?
I've read reports in the German mag c't about hobby radio people who complained that ADSL lines were interfering with their communications.
AFAIK the german T-DSL uses a slightly different standard than G.Lite to allow both ISDN and DSL on one line.
The main problem is that the user end of the line is not shielded and thereore both AM radio and the ADSL lines interfer.
Well in my area the cable line provider is also the only isp - no competition. There's one adsl line provider but lots of isps. My adsl line is reliable, and faster than cable in the area. My friends cable is always going down, and he averages half my speed. Cable users can't even saturate my *upstream* bandwidth (384 kbits/s). I wouldn't even notice when one is on my ftp if my router lights didn't flash.
I wouldn't get interferance from AM radio transmitters anyway, they're all on top of the mountians.
(adsl user, Vancouver, BC)
Cheers,
Rick Kirkland
What do you think will be more important 10 years from now ? The old low-quality mono AM radio or high speed net access ??
Oh, and until FM radio can be broadcast over hundreds of miles, which AM can do easily, there will still be a need for AM radio. There's a *reason* AM is still around, and it's not simply because stations own the bandwidth still.
Wake up, indeed.
- A.P.
--
"One World, one Web, one Program" - Microsoft promotional ad
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
Screw ADSL, I can't get it here anyway...but I can get Art Bell!
Will MPEG4 come to the rescue or will another line type?
--
Fuck the system? Nah, you might catch something.
Duh, Thats Elementry, why the hell would they need to have a study about that. Forty
Considering WBZ is one of the most powerful AM stations in the country (they even have a clearchannel), and it's huge broadcasting towers which send a signel sometimes heard in all the lower 48 states is within eyeshot.
50,000 megawatts of interfearance!
Just dumped my cable modem because of massive bandwidth loss due to too many people on my
segment. Scheduled to get adsl shortly as a replacement. The good news is at least i got
free installation and the dsl company also offers SDSL(for 3 times as much of course).
I think i shall not get rid of my dialup isp just yet. Kept it even after i got my cable modem just in case.
I think ill start sending e-mails now in anticipation, to all the AM stations in the area.
That should be about 40 e-mails if i remember correctly.
Actually what do people use there AM radio for? Probibly most listen to games
and Art Bell anyhow. If thats the case you can get online broadcast's of it all anyways.
off and out
The upload speed may not be affected, however it does give the ISP an excuse to option the upstream speed down and blame it on poor line quality. I have first hand experience and as a result I am now a cable ISP subscriber. :( hypedawg
Well, since my am cb causes noticable interferance to the phone line (not enougth to upset my modem), looks like i'll have to give it up before i get asdl.
Gee, leave it to /. to regurgitate a story posted on GeekNews like two days ago. God I love /.
Am radio has a lot more useful content, information and entertainment value then 99% of the crap on the web. Plus I can receive it from my car or pocket radio from (just about) anywhere. Besides I can't get ASDL anyway here in USWEST territory. No available lines or too far from the switch or whatever their lame excuse is THIS week.
That's why we have FM now !! wake up !
What do you think will be more important 10 years from now ? The old low-quality mono AM radio or high speed net access ??
AM will be around for a very long time to come. AM transmitters and receivers are far simpler to design and use far less components than FM.
Yes FM is higher fidelity but AM wins hands-down in the "simple to set up" category, which is important in any kind of emergency (I'm thinking TEOTWAWKI) situation.
They really need to turn over the radio spectrum to the public for short-range Internet wireless systems. On the other hand they should sheild those lines too. No reason to be stupid about it. :)
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
Maybe this might convince you slow coach Americans that adopting DAB is a Good Thing(tm)....
.'. DAB much be good right?
DAB uses MP3
I see amny folsk saying "kill the AM" but that is
actually not the problem, for as many hams know
you can have your transmitter all tuned up, nice
and clean, obeying the letter and the spirit of the
FCC rules... and still get complaints from neighbors
because they get interference on their shoddily
made stereo/tv/phone that picks up everything,
desired or not.
What is needed is not getting rid of AM (at least
not for that reason, the bandwidth would surely be
re-used by another service, result - same shoddy
equipment still has problems) but making things
that are not susceptible to perfectly acceptable
RF emissions.
Now if one has well built devices and they get
clobbered by illegal transmissions, overpowered,
spalttering, spurs, etc.. THEN you go after the
transmitter.
Geeknews is lame and since I don't go there, its not regurgitated to me. /. rules!
Actually AM is higher fidelity but I don't want to start an audiophile arguement ;)
Amateur Radio is authorized to radiate in the bands assigned to it.
ADSL, cable, et cetra are not authorized to radiate at all in those bands, the AM ones, or any other frequency; if it does, it is violating FCC regs. Simple as that.
In the end, CAT 5 UTP has more than enough twist in it to compensate for all but the most noisy environments. After that, you're running STP cabling, which more than likely means you are running your network over Token Ring (see 'signaling characteristics' above). Even nasty cheap-ass CAT 5 is going to be much better than phone cabling, hence your observations. The 'shielding' you think you are seeing is just a protective wrap for the wires, that way when people walk on them and what not the copper doesn't break between the jacks. This is also why you see stranded core used for hooking up desktops to the wall and what not, and solid core run through the walls (stranded core is less prone to breakage than solid when it comes to tight turns, people stepping on it constantly, etc. but it is more expensive - you can save money on your total plant cost by taking advantage of the fact that nobody is going to be stepping on and monkeying around with the cables in the walls that much).
Anyway, I agree, if you are having a house built or rewired, run CAT 5 UTP for both data and phone, or at least CAT 3 for phone. It does make a difference.
-- ultra1
The article didn't mention any frequencies on which the interference might occur.
My multisync monitor causes AM interference in my house, but my guess would be that the incoming ADSL signal would be much stronger in comparison.
To-do List: Receive telemarketing call during a tornado warning. Check.
I have ADSL, but have never noticed any degredation. However, there are several AM towers in the area, and I can get AM radio stations to play over just about any electrical device with a speaker. My old answering machine plays oldies, my old phone picks up interference, etc.
Is this because of the wiring in the house or the wiring going to my house? I would think it's the in-house wiring or the devices themselves because the phone lines are underground around here.
My ADSL wire runs only 15 feet or so to the splitter in my basement. Maybe I should really test my bandwith - very few things on the web give you an accurate idea of the speed. I'm supposed to get 2.2 Mb/s...
Dozer
"The dumber people think you are, the more surprised they're going to be when you kill them."
Dozer
"The dumber people think you are, the more surprised they're going to be when you kill them."
I live about a mile from KDKA 1020 in Pittsburgh PA, It's the oldest and strongest public radio boradcast in the world (some people can pick it uip in their dental fillings).
I have CAT 5 run from my Network Interface Device to my DSL adapter, not including the 4ft phone cable from the cat 5 to the dsl adapter. and I get most of my full bandwidth at 640K.
I guess I'm really lucky because I would assume that a lot of the 15% affected are near KDKA. (Or would be if Bell Atlantic would get more neighborhoods rolled out.)
I went through the trouble to get a Tech no-code, setup a datamodem on an aparently unused channel in the 70cm band, using 9600 baud soundmodem. I setup TCP/IP w/ internet gateway, and a little HAM bbs.
I then tried to get some locals using it..
I was told that I was unwelcome on the radio here. I was told that it's illegial to use TCP/IP on HAM freqs. I was told that Linux was communists, and it distroyed bussiness. I was run off the airwaves.
I sold my equipment right away (small investment as it was).
I think it's unfair of you to applaud amature radio, when it's users are so hateful of differnt technolgies.
Sure, higher fidelity, but the signal degrades more easily. Does anyone use AM Stereo btw?
And, if we designed them today, we'd use compression and massive error correction, probably reducing the bandwidth both need as well as boosting the fidelity.
FM radio did not obsolete AM radio. AM and FM radio now occupy complimentary niches in boradcast radio. AM for talk radio and newscasts, FM for music. Dumping AM will only further crowd an already crowded FM spectrum with stations that don't need 200KHz of bandwidth. Waste will increase. No, my friend, it's DSL that's fucked up and needs to deal with its own problems. You didn't really think that POTS lines running from the switch to your house, the same today as they were 90 years ago could just magically do high speed data without problems did you? Besides, hash in the AM spectrum comes from all kinds of places, not just from the AM towers. A blender, vacuum cleaner, fluorescent lights, dimmer switches, can all drown out nearby AM radio. This hash will still get into your DSL line as easily as AM broadcasts do. Or do you plan to ban these and other appliances too. JUST SHIELD YOUR FUCKING LINES AND QUIT TRYING TO BAN WHAT *YOU* DON'T USE, LAMER.
Pilots use AM radio to do adf navigation all the time. These stations are used to do non-precision approaches to airports. If this does interfere with AM radio stations, I can't beleive that the FAA has not done anything about it.
I can just see the headlines..
airplanes crashed because of Quake 3, news at 10.
My cableco (optonline) has no caps on bandwith (up or down) and they also dont seem to give a shit what ports i listen on. I see 300+K/sec downloads. I once sent a ISO image to my friend that is on the same subnet as me and it went at over 600K/sec. The router (3Com/USR) could do the full 10Mbits...but ive never seen that. Plus i have a fixed IP. For $39.99 a month im happy with it
I have to return some videotapes...
AM radio signals may be causing interference, but they're the ones licensed to be using the airspace. For crying out loud, what is going to be next? 'Basic laws of physics are making my network go slow'? If the technology is succeptable to AM interference, it is FLAWED, and the speed rating of the technology is dropped, and people have to DEAL WITH IT. It's not as if the bandwidth is necessary anyway, theres no way in hell ISPs are going to be able to handle hundreds of ADSL subscribers.. the subscribers are the ones with the cheap hardware and lines, the technology is fast but it sure as hell isnt stable (as demonstrated with this interference crap). The providers are the ones who need to roll out the huge cable backbones and stable systems. ISPs get a hell of a lot less bandwidth for their buck than subscribers. Not to mention the poor bastards who run webservers who once could serve thousands on their T3 connection, and now are paying for multiple DS3s to keep up. This technology should NEVER have been adopted by ISPs, and anyone who tells me that going higher than modem/ISDN for regular internet access was ever a good idea I consider to be the idiots who made the internet what it is right now... slow, unreliable, full of idiots with $25 a month cable pushing their entire CD collections to each other. RIP ADSL.
... little downtime, fast downlink, plus we get 256K uplink (rather than PacBell's paltry 128K).
I live in Portland Maine, and we have RoadRunner (Time Warner Cable). I routinely get speeds of 250-300k/s to major sites...I've heard @Home is bad but I have not experienced such problems with RR...
Currently, the only ADSL provider here in Bangkok advertises the following MAXIMUM ul/dl rates:
...128/128...
i reeled in horror the first time I saw the telco wiring here... unshielded and low quality cable is just the beginning. The price is paid in low low low ADSL rates, it seems.
Moral: Those of you complaining you'll only get 1Mb dl speeds can still count yourselves luckier than those of us in the big mango.