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Beware Of 2.4 GHz Interference
RobinX writes: "If you have any combination of cordless phones, wireless ethernet, wireless video, or Bluetooth you could be having problems. I've got two different 2.4 GHz phone brands that are interfering with each other and with my home 802.11b wireless ethernet network. It seems that the 2.4 GHz range isn't licensed so companies are free to do their own thing. Check out this article for more." I've been noticing problems recently as well, between phones from the same manufacturer and the WaveLan cards.
This isn't quite accurate. There are two flavors of 802.11 -- Frequency Hopping and Direct Sequence. I believe the author specified 802.11b which is the Direct Sequence flavor used by Lucent's WaveLAN and the Airport. (I may be wrong about which letter is which.) Frequency hopping equipment will indeed cause interference with the direct sequence equipment, since it's hopping through the ranges used for direct sequence pretty frequently. In the lab we've seen about 30% packet loss on WaveLAN when streaming full speed over 802.11a using the Raytheon 802.11 chipset used in WebGear Aviators. The Aviators seem to be pretty resilient though, and aren't affected significantly the other way.
Microwave ovens operate in the 2.4 GHz band, and are poorly shielded high power transmitters. Wireless lans and other ISM band applications are low power transmitters, but many microwave ovens (especially older ones) radiate (read: interfere) more power than these low power transmitters are allowed to do, because of their poor shielding. I would be very sceptical to use equipment running in the 2.4 GHz for "mission critical" work. 5.7 GHz ISM band equipment would be a better choice.
RFC1925
Regarding X10, my microwave oven interferes with the audio (mostly) on their ScanCAM product. Then again, the same microwave oven interferes with 60-66 MHz between the DSS box and the TV...
Miles Lott
It is sad to see this. I've been am ham since 1989. And, I find it alarming how the consumer electronics market pays so little regard for amatuer radio operators.
I think it is somewhat dangerous to allow the consumer electronics market to gain inroads, even at low power. The complaints filed against hams are only likely to increase because we may overload the cheap receiver front-ends on phones, LANs, wireless video transmitters, etc. I fear that the complaint of a large sector of population, as well as the consumer electronics market, would result in them winning the battle to acquire our dwindling RF spectrum.
Definately something to think about.
73 de KU4ZK
I used to play this star trek-ish game on my school's commadore PET, (I think it had a Motorola 680x0 CPU of some kind?). The manual stated that for sound effects, you tuned an AM radio to a certain frequency, and it picked up RF from the CPU. It worked. You'd get all kinds of buzzing and whirring noises as the ship fired and maneuvered on the screen.
If it ain't broke, fix it 'til it is!
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
It's perfectly legal if you have an amateur radio license. I could legally setup a 500 watt ATV (amateur TV) transmitter on 2.4 GHz. If it wiped out your wireless LAN, that would be your tough luck.
Another often overlooked culprit around this frequency band is the microwave oven. These run in the neighborhood of 2.45 GHz (give or take). Even a small leakage from the RF shielding can produce a detectable signal on or about this frequency.
Also, the the band from 2.3 GHz to 2.45 GHz is (and had been for quite sometime) used by amatuer radio operators. A higher powered ham tramsmitter could also be a source of interfere with this equipment. Technically, low-power consumer equipment should have been located on another band.
Poorly designed equipment can "mix" signals on different bands and hear interference on their operating frequency, also.
So your argument is that just because we don't have conclusive proof that there is indeed a cause and effect relationship, we shouldn't care?
As time goes on we are relying more and more on RF equipment. We are bathing ourselves in EM radiation. Have long term exposure studies been done?
What about non-cancer effects? The brain is nothing more than a large, wet, electochemical device. It is suceptible to EM feilds. We have known for more than 50 years that EM feilds in the microwave range can cause psycological effects.
So...these are low power...I understand that, but what about long term effects. We are fast aproaching a world where we will be exposed to this stuff to chronic low levels.
I simply mean to point out that we have evidence that there may be health issues involved and that this really needs to be considered. People should be informed so that they can ecide for themselves about the possibility of risk involved.
"I opened my eyes, and everything went dark again"
440Mhz is in the amateur radio service band. A warehouse full of lights putting out that freq would probably draw some vigilante action.
How many people have to suffer a harsh punishment before "cruel and unusual" returns zero?
My brother in law was a Marine, and he operated Hawk missile batteries. They could train the illuminator on seagulls a half-mile down the beach, and knock them out of the sky, basically cooking them in their own juices in seconds.
There are stories about burning people at range (without their knowledge), as a joke. But I think that falls under "urban legend".
If it ain't broke, fix it 'til it is!
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Back in '85 when I was in college cordless phones were something of a novelty, but were inexpensive enough that upper-income college student could afford them. The best part was the fact that they were all analog (43Mhz) and used the same 10 "channels".
The across the hall from me had a scanner and a cordless handset with jacked up power. We used to LOVE to use the scanner to find cordless phones and then "hijack" their base stations to do stuff like call the dorm office (owing to the University's PBX, it had caller id) and make all kinds of obnoxious requests, knowing that if we made enough of them the guy would get busted, as well as free long distance calls, and other phone obnoxiousness.
Pornographic and semi-pornographic conversations we heard all the time, and if we would have had a DTMF decoder and mag stripe writer we could have emptied a lot of bank accounts as bank-by-phone gives away all the info you need to make unauthorized withdrawals.
To this day I only use digital cordless products for casual conversations, and corded products for financial transactions.
Well - I'm working on my 100 Watt transmitter ;-)
for 2.4 Ghz to talk to the guy in the next town over. Hmm - maybe I'll build a spread-spectrum repeater on that band. That's the ticket - oh yeah - a amateur radio ticket
The point of the story is - all this stuff is un-licensed (as has been pointed out before) and ANY licensed service has priority(in the US at least.) So if I DID build such a repeater, it would have priority, and all those neato devices that work at 2.4Ghz would have to accept/deal-with any interference caused. This whole story isn't news. The same thing happened to the 900Mhz band a couple years back. In my area the Richochet service pretty much trashes the entire band for any other use. Hmmm - Maybe a 900Mhz frequency hopping spread spectrum repeater...
Have you compiled your kernel today??
While neurons carry current, using chemical electrolytes, I don't believe that you can induce a current in a neuron via EM radiation. If that were true than everytime you were subjected to EM radiation or a high magnetic field you would start shooting lightning bolts around, and I haven't seen this yet.
-- Remember: Wherever you go, there you are!
No, instead it's made out of electrolytes and ions that serve to send electrical pulses along the surface of partially conducting neurons.
It ain't just copper that carries current.
Anomalous: inconsistent with or deviating from what is usual, normal, or expected
Anomalous: deviating from what is usual, normal, or expected
Canard: a false or unfounded repor
Resonance of various frequencies with various materials is due to the length of a specific wave with material that consists of particles of the same size as the wave length. Let's say the wave length is 1 millimeter than dust with diameter of 1 millimeter will resonate with this frequency. The power of the wave also matters, since more powerful waves will hit the particles at higher speed and more waves are produced with higher power for equal time periods. 2.4GHz is a frequency and does not tell you what the wave length is, so we are missing the wave length to find out exactly whether this wave length is the same 'size' or length as a water molecule diameter. Now if a wave length of size of a water molecule is directed at some water container with frequency of 2.4GHz that water may boil in seconds because of the resonance, the wave will not go through the molecule (as would have happened if the wave was much shorter) and it will not go around the molecule (if the wave was much greater) but it will 'fit' the molecule size and will cause it to move much faster and faster moving molecules give out heat.
You can't handle the truth.
This sounds similar to every NEXTEL phone that I've ever seen -- it has the power on the bursts of digital data that can actually put a stereo or simple computer speakers into fits whenever it bursts.....
:)
Karnal
Cisco bought Aironet, but the terms of the agreement mean that Telxon are still the easiest route to go through.
Symbol also do an 11Mbit DS system, but aren't pushing it 'cos they're waiting for the 25Mbit kit, which could be out this Autumn.
Lucent do a good one too.
Frog51
Frog51
The generic term for that is Hiroshima-level EMP device. Plan for replacement of the device after a single brief use.
There is a UK TV program called watchdog - they bitch about everything to everyone - its an ok show, there was an epp recently about some company in the UK the put up a nice big antenna on their site for all the radios and whatnot they use, its perfectly legal, has correct license and what not, BUT no one in the town can watch TV anymore because the TV signal boosters that everyone requires because the Terrestrial TV signal sux also amplifies the signals from the companys radio network, the company is trying to contact the manufactures of the booster equip so they make them just boost the TV signals, - I fought it was funny :) - would tell you the name of the place and company, but I didnt hear that bit - damn brother bitching about something!
Although they are shielded they still produce a lot of noise (because a typical microwave can have up to 1000 Watts of output power). Most wavelan devices should besides a bandwith drop not have any real problems with it. Video transmitters do have problems with it!
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
Actually its neither one. The wavelength of a Cellphone is closer to the microwave then radio and TV. I don't have a technical explenatition but it has indeed everything to do with interference; one signal influencing the other.
Bluetooth frequency hops at 1600 times a second. But from what I recall, IEEE802.11 hops at a much lower rate, just a few hundred times per second.
I also remember that if you installed a bluetooth device and a wireless LAN card in the same PC it would kill the LAN. But then I haven't heard anything more about that problem for quite a while.
Could this just be a case of poor receiver design? I've seen this is VHF/UHF receivers. A strong signal will produce intermodulation distortion in the front end and wipe out any weak signals. A good receiver will have a linear front end with a wide dynamic range. This costs money, which probably means that the receivers in consumer grade equipment are a major cause of the problem.
Mea navis aericumbens anguillis abundat
This article gives very little detail on whats going on here. They don't even say if the author even tried adjusting the frequency settings of the interfering components. 802.11 has 11 (in the US) -non Frequency hop mode frequency settings (most of which overlap) and selecting another one might have helped a bit!
:-(
Some background for the curious: 802.11 sends 'chirps' - the same bit is sent simultaniously on a range of frequencies, with some bits reversed. this is done to prevent interference, or blocking on one band from interfering with the transmition.
The channels look somthing like this (in ASCII anyway) (if this looks wrong, paste it into an xterm, or notepad, or somthing with a fixed-width font)
|
|............---7---
|..........---6---
|........---5---
|......---4---........---11---
|....---3---........---10---
|..--2---.........---9---
|---1---........---8---
+---------------------------------------------
frequency ----->
Note that the vertical axis doesn't represent anything, it's just used to stop everything going on top of everything else. The dots are there because slashdot slashes spaces, but leaves dots! Nor is this diagram accurate, or to scale or anything, it's just ment to give you the gist.....
Here each ---x--- is a range of frequencies over which the bits of the chirp are spread.
There only one set of 3 channels which don't overlap, so if you need more than 3 802.11 networks in the same place, you're our of luck.
If you run your network in frequency hopping mode, you only transmit one bit on one frequency at a time (chirps send about 12 bits), but change frequencies often, across the whole range (no channels) This means that interference on one range will only kill some of your data. You obviously than need to retransmit failed sends (by the time a retransmit happens you will have switched to a different frequency.
The quality of the hardware you use can also make a big difference. The better equipment uses two aerials, spaced apart, to prevent reflected signals and some other kinds of interference from silencing the signal. The idea is that if a signal and it's reflection interfere to create a minimum (no signal) at one point, there will be signal just a short distance sway.
Most devices just ship set to a channel, and it's nearly always the same one - surprise surprise - 1! I don't know about the phones, but they would probably be similar.
I guess no detail, or background research is about what we expect from ZDNet.....
I'd suggest you go over to the residential zones surrounding Lopik and talk to the people there. After you did come back here and we'll talk again.
But what is to be done about this? Surely those designing the technologies realized this would happen at the time? Isn't all this spare current running around inside my electronics going to damage it?
Most importantly -- who should I sue? :-)
And very limited spread. IIRC, 6 bits of real data for every 8 chips sent over the air. Consider yourself lucky if it works at all with another 2.4Ghz device.
Jingling your keys would make the TV very loud and turn the picture green. Lots of fun.
I wrote parts of this stuff
I am a grad student at CMU and over the past few months the Multimedia Wireless Group has conducted a series of outdoor tests to quantify the interference between 802.11 DSSS and 20dB Bluetooth trancievers. The results are curiously interesting since at close distances the packets lost are max (highest SNR), at medium distances (30 yards) the interference is minimum and at far distances +80 yards) the packet loss increases afgain (falling SNR). Slashdotters are welcome to take a look at the MatLab plats and send me their comments. The data and plots are available via email (mangets@hotmail.com)
1. If you are experiencing problems with your cordless phone, try adjusting the operating frequency of your access point. Any AP worth thier weight will allow you to choose different frequencys to operate on, all within the 2.4 GHz band. Most commonly: 2412, 2417, 2422, 2427, 2432, 2437, 2442, 2447, 2452, 2457, and 2462.
2. Access Point placement: Make sure to place your AP in a strategic location at your home/office. Central locations work best, and make sure your orientation is correct for the kind of radio you use. A bad place to set one of these things is next to your microwave (for obvious reasons)
3. Cordless Phone base placement. Minimize multipath transmissions by keeping your base station away from corners. Multipath transmissions from your cordless base station can and will take down your wireless network as it confuses your client radios on your other PCs due to all the 2.4 GHz traffic in the air.
4. The new Lucent 6.0 driver for their ORINICO WaveLAN cards has a new feature called "Microwave Oven Robustness." When this feature is enabled it prevents the radio from falling back to less than 2 MBit/sec when it thinks it is in poor coverage. This should only be enable in environments that will not experience fringe/poor coverage, however it should help your problems with interference if it is enabled in a good coverage area.
Numbers two and three are probably the most vital in getting multiple 2.4GHz devices to co-exist, so try many different placements! Try not to get discouraged, it does work!
-- Ian
Time for me to dig out the old 27Mhz phones... Nobody's on that freq anymore - they all dem newfangled jigahurts stuff. And I won't nuke my brain!
My remote control cars ran on 27 and 45 Mhz - played hell with the phone sometimes... now I just get this popping noise in my 900Mhz phone... only sometimes, but when it does it's about a pop every three or four seconds. Rather annoying.
"It's tough to be bilingual when you get hit in the head."
I am a grad student at CMU and over the past few months the Multimedia Wireless Group has conducted a series of outdoor tests to quantify the interference between 802.11 DSSS and 20dB Bluetooth trancievers. The results are curiously interesting since at close distances the packets lost are max (highest SNR), at medium distances (30 yards) the interference is minimum and at far distances +80 yards) the packet loss increases afgain (falling SNR). Slashdotters are welcome to take a look at the MatLab plats and send me their comments. The data and plots are available via email (mangets@hotmail.com)
Read meat doesn't cause brain tumors... I'd like a pointer to any valid studies that you know about that actually show that read meat causes brain tumors.
"It's tough to be bilingual when you get hit in the head."
This reminds me of RC car days, when you carried 3+ crystal sets on you so you could change freqs that your servo/transmitter used. If someone else had your same freq at a race, and neither of you had spare cyrstals, SOL to one of you..
Same thing here, pretty much. A (semi-)open band, and people are gonna use it for pretty much everything they can. History repeats itself as always, go figure. Wish I knew more regs on this so I could say how things are supposed to be.
bash: ispell: command not found
This sig left intentionally blank.
I saw a while back on Ars-Technica that some pagers and cell phones share the same freq as the master oscilator in AMD boards. When the pager went off, the computer would die! I think the guy fixed it by building a grounded box around the chip.
I'd rather you do it wrong, than for me to have to do it at all.
My microwave zaps my 2.4Ghz Phone, only thing that does it. But because it's DSS, then it only pops in and out a little, when it's frequency hopping happens to land on the one of the noisy freqs of the mircowave.
Now, in theory, a large number of DSS devices can share the same range of freqs because they spread out and "randomly" hop from carrier to carrier, supposedly fast enough not to cause an issue. It's a bit more complex than that, as the bits are encoded, then a DSP does some mangling to broadcast some info on one carrier, and other info on another carrier...
However, if you've got an analog 2.4Ghz phone, your screwed, or even a digital, if it's narrow-band and not DSS. Narrow-band will work if it can select a "channel".
Company I work for does interesting stuff with power-line communications using both DSS, and dual-channel Narrow-band communications. Both types of communication beat the hell out of anything else I've seen for reliability, but they have different strengths.
If you're interested: http://www. echelon.com/products/Transceivers/powerlinePresent ations.htm contains presentations about this kind of stuff. The technology update presentation contains information about the different strengths of DSS and narrow-band info. It covers power-line communications, but the same applies to air-waves, just that there is much, much less distortion... Which is why DSS works so well over the air.
-WoodyMy point excactly. How will these radiation affect our nevral nets, how will it affect the inside of our nevrons? Of course we have a much higher tolerance of fault in our brain than electronic equipment, but that doesn't mean we're invulnerable.
:-)
But, anyhow, if we just ignore the problem it will probably go away huh?
- Steeltoe
http://www.debunkingskeptics.com/
You can't have unlimited receivers, but since each is only getting a very small piece of the available energy it looks unlimited. Unlimited power is also impossible because of some stupid law that says that the total energy is constant. (you can't get more out than you put in)
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
Well, that prolly means that I'd have problems at college with suitemates having interfering devices. And I was so hoping to have that wireless ethernet surfing the net out in the courtyard...
First, I'm not a raido expert at all, but has anyone done real testing to see how each of these devices are causing each other problems. 2.4ghz has been un-lic for a while without problems, (yes it has gotten a lot more popular). I think some "real" testing should be conducted. I'd hate to see wireless devices take even longer to implement ...
Ok, let me rephrase. MY phone that operates at that frequency has no encryption, and experiences interference
Eh...
... the band range the licenses for which the German government is about to auction off with an expected profit of $50,000,000,000 ?
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
It's the cancer-causing meglawaves emitting from the phone interferring with the noted devices.
-brain
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
Heh - someone noticed :-)
It's even funnier with cheese.
-----
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
The short answer is that the X10 Video Sender is a piece of ca-ca and was the source of all of the problems. The other 2 devices do frequency hopping and spread spectrum transmissions to avoid (and compensate for) interference. The cheesy X10 device just blasts away on a fixed frequency with a very low quality transmitter that spills all over adjacent frequencies.
The best answer I found was to stick to 900 mHz phones and run a wire for video. I boxed up the Video Sender and gave it to my Dad. It was just a bad idea all around.
Shut up and eat your vegetables!!!
It's important to note that this is actually limited to digital phones based on TDMA (like GSM and IS-136), where the transmitter is switched on and off rapidly several times a second, since there are many phones (8 for GSM, 3 for IS-136) on the same channel, time multiplexed. Each phone is allocated a timeslot during which it transmits, and remains silent the rest of the time. CDMA based digital phones don't exhibit the same behavior... Put a CDMA phone next to a speaker and you won't get any interference, because the transmition is continuous (and it's also spread over a wider channel, this might have something to do with it too).
There's been some problems with France having to suddenly free up this freqency in order to comply with EU regs, as it was used by some (?)military kit.
Also in the US some old Life Support system used on 2.4Ghz for something. They were supposed to be phased out before y2k hit, but they weren't and test transmissions killed them (not to mention the poor humans attached to them at the time!).
How did you get a standard Aviator 2.4 card to talk between Windows and Linux? I had translation/encapsulation issues that could only be resolved by going to the better firmware of the Aviator Pro's.
By the way, Aviator tech support was some of the nicest people I've ever dealt with to get this resolved.
Tim Gaastra
Tim Gaastra
Build a better mousetrap and the world will immediately get their fingers caught in it.
Now the digits are having to learn about the black world of RF. go to the the web site www.arrl.org and brouse through the many books on RF including the do a search on RFI and some articles come up regarding FCC regulations and current interference laws. One comment, doing wireless communications will not be as easy as many think. Just dust off that old CB radio (if you have one) and just listen in. There is so much interference going on you cannot understand anyone. If you have access to a spectrum analyzer that you can connect an antenna to you will be able to see all the RF signals being transmitted in the band of interest. Maybe now the schools will start to teach RF engineering again.
If I'm right, microwaves, since they are a form of electromagnetic radiation (EMR), travel at the speed of light (through air), c. Thus, to find the wavelength, you just take the velocity and divide by frequency (c/f). My point is that the frequency DOES tell you the wavelength.
-----
Obviousness is always the enemy of correctness. -- Bertrand Russell
There IS an alternative. FHSS systems are not plagued by these problems.
802.11 is more than the 11Mbps radios.
I say, "Hey! direct sequence has colocation defecits", and they say "but it's cheap!", and now everyone complains...
http://www.midcoast.net/wirelessfaq.html
DSSS systems are flawed as they are not capable of coexisiting with more than one or two other devices. ISPs are rolling out service based on DSSS and when Mabel lights up her cordless phone, it shuts down the service... and I say, "Hey! direct sequence has colocation defecits", and they say "but it's cheap!", and now everyone complains...
Cheap is good, but if it fails to function, it is wasted money.
Telephone broken?
Waves lie heavy in the air.
Where's the damn tin-foil?
Tis true, and sorry that I obviously did not make myself more clear.
As you say, the problem is not what frequency it is on. The problem is that everything seems to be moving up here.
However, it does not matter whether it is spread spectrum or not. Yes, that is going to help, but it is not the total solution, either.
First, there are a limited number of frequencies there at 2.4 that can be used. Add to this that not all devices work on each of these frequencies. They may use 1, 2, 5, 10, or 20 of the frequencies. Next, even if they are frequency hopping there is a limit to the number of things that can be on a given frequency at the same time.
You mentioned that some devices don't frequency hop. True. So, if a device is in use and it does no hopping, that frequency is pretty much useless for devices that do hop.
We are seeing so many things using RF nowadays. And we are going to see many many more. Hell, I love wireless things. But I also realize that the more things I own, the more the possibility that they are going to start colliding. That is why I try to spread out between the different bands.
You don't need a license for the 2.4Ghz ISM band.
This is the band that your microwave oven works in (though that is supposed to be shielded)
Really, it's only licensed for spread spectrum use, either FHSS or DSSS.
And yes, it is possible for the two to smash each other. fhss devicess will tend to not smash each other.. and dsss won't either, as long as power levels are reasonable, but if you mix them.......
Boosting your own power would just make the problem worse for everyone else.
The article only dealt with interference between the gadgets of one person. What would have happened if the author had a neighbor who also had a bunch of wireless stuff?
This is really disheartening about the near-future of wireless. If a few wireless things can't co-exist in one person's house, then cities are doomed. So wireless will be great, as long as you are the first one with it and only until your neighbors get it too.
Hmm. It it's so bad that stuff like stoves can go crazy, what happens to people with bionic ears and pacemakers?
---
You are right about radio and tv equipment being disturbed, but trains moving on there own is bullshit.
He is probably talking about model railroads. I consider this to be quite likely - during my first physics courses at college, the professor showed us as an experiment how you could bring a light bulb to glow by simply connecting two wires of a specific length to it and holding it in the proximity of a radio transmitter antenna with sufficient power. In fact, he told us that for some time, this was a cheap albeit illegal way for people to light up their garden sheds near a TV transmitter station in the first years of broadcasting. If the power cables to the model tracks and the tracks semselves have the right length (a multiple of the wavelenght broadcasted), it should be entirely possible that the trains could start running on their own.
Cthulhu fhtagn!
This is like saying "When I bang 2 cans together on my head, they make a noise." Of course they're going to interfere! They work on the same batch of frequencies, just like CB radios interfere with some radio controlled cars.
Coming up next on Slashdot, "When I go outside in the rain, I get wet. Why is that?"
Next they'll be posting ingredient lists from cans of beans...
Unless you have a pre-GSM analog phone, which I know nothing about, then no, cellular phones in the UK don't transmit a 3-5 times the power used in the rest of Europe. Handheld units for GSM 900 output up to 2 watts, and GSM 1800 up to 1 watt. In reality the power is usually less than that, and it's determined by the network based on the strength of your signal when it's received at the tower (ie it's going to be really low if you're really close to the tower, and much higher if you're far from the tower and/or there is something blocking your signal).
I agree 100% with your technical analysis, but lets reformulate it in layman's terms that will help everyone, without need of any specialized knowledge. It's a basic principle of troubleshooting life in general.
You say he should have unplugged the X10 first, not last, but if the X10 video sender is predominantly at fault, he'd have unplugged it first *and* last. When unplugging a device fixes a problem, you don't usually keep unplugging things. Instead, you say "Aha! found the problem" and stop -- or better yet, plug everything else back in.
This practice can cause untold grief - but it usually works extremely well.
This author assumed he had a generalized or cumulative problem. he probably got this idea from the service personnel he contacted, particularly (assuming the X10 video sender was primarily at fault) the X10 service people, who implied that 802.11b devices don't play well together.
Well you can hardly expect them to say "our device doesn't play well with other 802.11b devices", can you? Heck, they may never have thought of it that way. All they know is that they see 802.11b problems left and right. they don't know other companies (or device types) don't experience this degree of problems with each other. (or maybe they do, but they have a peculiar wish to hang onto their jobs and.or see their company stay in business)
When you find what you think is broken, see if everything else works together. If it doesn't you have an additional problem -- but there's no need to presume more trouble than you see.
It's just common sense... and we all know how tricky that can be!
Freud would probably have something to say about that...
That said, I think it's time I changed my
You'd think that these manufacturers would learn from history. Just look at the jump to 900 MHz for phones.
As little as I know about wireless phones, the skinny of it is that as more people are using the phones, the more 'channels' needed to they wouldn't intrude upon one another. The same idea at 2.4GHz. The difference, to me, is that there is more room for more of these channels. Why the companies aren't taking advantage of that, I don't know.
And unbelievably, 95% of the people who experienced sightings ingested water with 24 hours of their experience.
My father was an air traffic controller in the air force and stationed in Newfundland, and he has told me of guys hopping in front of the radar array for a second or two to warm up when on patrol. (Didn't say anything about eyeballs poping like eggs in a microwave, nor testicles.)
Yes, but you also can buy bulbs with smaller power consumpition - e.G. for the chandelier type of lamps.
Cthulhu fhtagn!
They're switching to IR speed detectors to better catch speeders. (Radar detectors don't work on laser). As for radar, "instant on" helps catch speeders and reduce health risks. Think most cops today are broadcasting radar 100% of the time? Probably not.
Just because it CAN be done, doesn't mean it should!
a) have slept during your 'technical studies'
b) have equipment that does not comply with standards regarding radiation sensetivity
c) live so close to the transmittor you can piss on it.
Slashdot poll?
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
It was something the line of "theft of electrical power". Yes, the power in question is freely distributed, but not with the intention of lighting your rooms :-) IIRC a device like a rigged-up bulb consumes much more of the electromagnetic field's power than a TV set, and by this somehow distorts the field. This distortion can be measured, so the broadcast station operators can locate where their power vanishes. I don't know whether there are laws agains this kind of theft in all countries, though.
Cthulhu fhtagn!
This is very interesting.
Now I know the power output is nothing like that of a microwave oven but, it does make you think. There have been links made between putting cell phones next to your head and brain tumors...
Beyond that... it is well documented that electromagnetic waves in the microwave range can cause psycological effects in humans (in fact, I believe this was one of the many things that certain government agencies did some research in to see if they could use it to modify behavior)
I have to wonder what the long term effects of "imersing" yourself (for lack of a better term) in a "bath" of low power microwave rane EM radiation is.
Interestingly, health risks are exactly the objection that a co-worker of mine cited when we talked about deploying wireless ethernet in some places around campus...his background? Well he is a HAM radio operator and said "I know the risks and I voluntarily use the equipment with that knowledge. What about people who just happen to be nearby and don't even know its there - they don't get a choice" (or some similar sting of words to that effect...was a few weeks ago)
Food for thought.
"I opened my eyes, and everything went dark again"
It was an incandescent bulb. The teacher also showed the experiment with a fluorecent bulb (a "neon tube", I don't know the correct english description for that).
Cthulhu fhtagn!
Still not very likely since if fifty people would be able to light such a light bulb nobody would receive anything since all power goes to the bulbs.
I think that's the main reason why it is illeagl to light your house this way (at least in some european countries). Since a power drain like this somehow distorts the electromagnetic field, there really is less power available for the TV antennas.
Cthulhu fhtagn!
Back in the 70's some friends of the family had a remote control TV. Their little boy had a fire engine toy that rang a bell when you push it along the floor. Everytime the bell rang in the same room as the TV, the TV changed channels!
You can see why ultrasonic remotes went the way of the dodo.
Pope
Freedom is Slavery! Ignorance is Strength! Monopolies offer Choice!
It doesn't mean much now, it's built for the future.
You need much more for a motor to run then for a light bulb to glow, a typical electric train runs at 12V with about 0.1A (some up to 0.5A) That would require at least 1W of power. To pick up this kind of power you would have to live VERY close to the antenna, and I know Lopik, there are only a few people living really close to it and I don't think anybody is that close to it. Besides Lopik doesn't cover the entire country, there are several substations accross the country. Which again is only a few hundred kilometers from one end to another.
Since a few years most transmittors have been moved to a more remote area in the FlevoPolder anyway.
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
What can be done?
Well, the basic thing to do is to prevent high frequency signals from entering you audio equipment.
How do the signals enter? By the wires. Wires with the right length function as antennas.
What can stop the signals? Anything with induction (coil) effects.
(Any amateur radio operator will know this, since they send signals with several 100 more power than any license-free device. Ask a HAM if you know one.)
Put a ferrite core around every wire leading to or from your audio equipment, as close to the enclosing as possible.
Look for ferrite cores in CB/walkie talkie shops or in HiFi-freak stores.
-- From Denmark
In /. technogeek is the common language. Emmerse yourself in and learn.
now we need to go OSS in diesel cars
We've been having these exact issues. Which is why we rolled out base stations to IT Operations for "testing" purposes at home and almost immediately ran into the 2.4 gHz cordless phone problem.
Having said that, once you're aware of the potential interference, wireless connectivity can be a real, real benefit. For base stations we're only using one official WaveLAN base station, and for the rest (including the home units) we're actually using Apple's Airport Base Stations, which are working very well.
The key to good performance, we've found, frequency issues aside, is to make sure to configure each base station to accept only certain mac addresses and space these out. This will ensure that if people walk around with their laptops, you won't suddenly have an issue where 30 people have a meeting and they're all using 1 base station. Especially if one of these is giving a streaming video presentation....
So, highly recommended, despite the various interference problems, which we've managed to overcome, to a greater extent. Just plan, plan, plan, as always....
The techincal explanation is about sum and difference frequencies generated by non-linear components.
Since you audio equipment is full of transistors and diodes (both of them non-linear) any incomming high frequency signal may be converted to a signal in the audio range. See my other comment about how to stop the problem.
-- From Denmark
But what is to be done about this?
You have several options: 1) Make sure you have a good signal strength to your base station (lowers the transmitted power from the phone). 2) Use an external antenna (moves the radio source). 3) Just move your phone a bit. The noise in my computer speakers vanish completely if I put my phone more than a meter away from them.
To get a good signal to the base station, move your phone around a bit. The signal can vary a lot in a small area. It also saves your battery - keeping in contact with a bad connection sucks much more power than with a good signal strength.
In fact, there were (still are?) enough people with analogue cordless phones about that you could wander around in a car with a handset until you got a dial-tone, then park up and "borrow" their phone line for a while
Disclaimer: I, of course, have never done this myself...
Most countries in the world limit the 2.4GHz band - although it is unlicensed - by power output. The US gets 1 Watt max, UK and Europe get 0.1 Watts (France keeps changing its regs) and the Middle East still hasn't fully complied:)
Frog51
Frog51
Unfortunately, the 802.11 Frequency Hopping standard does not allow the device to learn which parts of the frequency range are interfered with. It would be nice, but it just can't happen, as it would screw up so many other parts of the standard.
Sorry to disappoint
Frog51
Frog51
Yes but you dont need to induce the power into the enginge. Mess up the controls and you could get a freghttrain to run amok. It has been done with planes ( cellphones, you know the rest ) Perhaps you should enlighten us? How exactly _did_ such a low-power radio such as a cell phone mess up the _controls_ of an aircraft? No, you are horribly and woefully misinformed. (or you completely lack understanding in this area, in which case you shouldn't say anything) What happens with cell phones and aircraft has nothing to do with the controls, but the navigational equipment that recieves radio signals. Since these devices are likely to overlap in the frequencies they use, it's not such a huge leap of logic as to why such navigational equipment might not be very accurate under these circumstances. It's also worth noting that freight trains do not need radio navigation equipment to find their way. You shouldent underestimate the strangeness of things that can happen when dealing with HFEM radiation. Riiiiiiight. Seen any funny lights in the sky lately?
---
"No problem. I have the capacity to do infinite work so long as you don't mind that my quality approaches zero."-Dilbert
attribution should go to Monty Python for the original of this post.
And on most wireless phones and LANs there's only ONE preset frequency, and since it's neatly set at EXACTLY 2.4 GHz, ofcourse they'll interfere...
I don't know about wireless phones, but wireless LANs (at least 802.11b) usually have the option of 11 frequencies in the 2.4GHz band in the US. Other areas of the world have different restrictions. Usually a 5 channel separation will eliminate interference from other 803.11b devices, so if you are using channel 6 and your neighbor is using channel 1 and your other neighbor is using channel 11 their shouldn't be a problem.
This is supposed to be great art. So why does it look like a bunch of decapitated naked people? -- Calvin
This generally shouldn't become an issue, as the 802.11 standard allows for intelligent loadsharing (assuming rf coverage by more than one AP).
Certainly, we like to overlap quite heavily in industrial areas - continuous coverage by 3 AP's for any mobile device pretty much guarantees robustness (for hw fail or congestion) - of course using Voice over IP over 802.11 rf does mean we need nice fast routers in there as well:)
Frog51
Frog51
Sounds like the explaination for our problem at home with our wireless cards. We randomly drop signal from one of our laptops in different parts of the house, that is after it has been working fine for 30 or 40 minutes.
:)
I used to sell guitars in a large store when I used to live in Dallas. You could not use a wireless, electronic tuner to tune them because the overhead flourecent lights put out 440MHz which is an "A". Or so said the other guys who worked there. I just wanted to jam..
Well, the phones have a whole stack of problems in their own right. First, any idiot can tune in to them (no encryption). Second, they interfere with each other a lot. You're not likely to notice the second, unless you live in between a college dorm and a college sorority, like I do (thank you God). At any rate, I'll keep the 802.11, and I'll keep the phone, since nobody really cares what I am getting on my pizza.
Eh...
Sure. If your nervous system were made out of copper wire... Is it?
---
"No problem. I have the capacity to do infinite work so long as you don't mind that my quality approaches zero."-Dilbert
Man, first its kids getting all hopped up on "Placebo", now this "Wireless" stuff!? When will the madness end?!
It's 10 PM. Do you know if you're un-American?
--GrouchoMarx
--GrouchoMarx
Card-carrying member of the EFF, FSF, and ACLU. Are you?
Just a simple statement: generally, with digital
transmissions, the higher the bandwidth, the wider
the signal. So, that being said, 10Mb on 2.4Ghz is
a relatively wide signal, and is going to step on
stuff. This is the pandora's box of "everything"
going wireless. It won't be solved until more and
more devices incorporate "software radio" techniques and know how to back-off of an active
channel. Then, more, but never an infinite or even close, number of devices will be able to co-exist.
This is a classic problem. There is only so much [currently] usable spectrum.
BTW, sheilding has very little to do with it. It
affects it some, and can cause co-channel interference, but the bigger problem is the fact
that a 10Mb signal is _very wide_.
cvoid - satellites are cool
Actually...
It has been known for more than 50 years that Electromagnetic feilds can effect the functioning of the human brain.
In fact, it was experimented with for much the same reasons as LSD was back in the 50s and 60s by organizations like the CIA.
"I opened my eyes, and everything went dark again"
I heard a story about a couple of Navy guys who wanted to do a bit of birth control before they went ashore. So they stood in front of the on-board radar array...for about 5 minutes. I think they realized they had cooked their insides about 10 after that.
--
+&x
I have a rack of machines with FM tuner cards that recieve and stream FM radio for local radio stations on the net. The things are all hooked up to a cybex KVM switch (AutoView 200) with a "longview" extension that runs the video, kbd, mouse, etc over a piece of Cat5 200 feet away.
For some bizzare reason, the Longview box spews all over 107.9MHz making it impossible to recieve that radio station inside of the office (I had to go with a roof-mounted antenna)... The other funny problem with 107.9MHz was that whenever I tuned one of the radio cards in the rack to the station, one of the computers would crash! I taped a piece of lead foil around the chassis. I think it was screwing up the SDRAM (whose oscillator was probably a little bit funky and going at 107.9MHz!)
~GoRK
2.4GHz is one of many, what the FCC calls, ISM bands (Industrial, Scientific, Medical). It's an unlicensed (below a certain power limit) free for all dumping ground for RF hash. Not actual communications, but for hash. Noise. Spurious emissions. Unintentional radiations. Truly a WASTELAND. Sure you can make gadgets that communicate in this band. But don't be surprised if your transmissions get stepped on once in a while. And don't expect to have any recourse. "This device must accept interference, even interference which may cause undesired operation".
All of this is really cool, having an AP and cards for your laptops/PCs.. But what about bridging two networks together?
I am in a situation where all the PCs are networked together (wires), but I could link two networks, about 1-2 miles apart (maybe even less) using wireless stuff.
Is there such a thing as Ethernet-to-Wireless bridges that I could use, (I guess with directional antennas) that would not require other physical changes to the respective networks?
I could also be interested in any solution that would bridge the networks, but still provide an AP to local users, should I decide to go wireless for the laptops...
Obviously, these will probably cost more than your regular home stuff...
Anybody has experiences to share?
Pointers? Suggestions? Comments?
73s from ve2asm
The 2.4GHz spectrum band is "unlicenced", and more commonly known as ISM (Industrial, Scientific, Medical) band.
It spans a frequency range of 2.4350 - 2.4850 GHz, which is broken down into 78 channels.
There are two types of Spread Spectrum technologies in use: DSSS & FHSS (Direct Sequence Spread Spectrum & Frequency Hopping Spread Spectrum).
DSSS uses 26 of the available frequency channels for its transfer signal, this is a contiguous block, and is very sensitive to any interference.
DSSS specifications call for 11 possible channels, overlapping, with only 3 non-overlapping channels. (this means it is only possible to co-exist 3 seperate DSSS networks/devices)
Under US/FCC regulations, the full spectrum may be used, so 3 DSSS networks will co-exist, or up to 26 FHSS (in practice, 15 more realistic).
Under Canadian/IC regulations, only 1/3 of the spectrum may be used, so only 1 DSSS network is allowed, with only 1 possible channel, while FHSS will allow 8-10 networks)
The FHSS network standard is 802.11, which is officially 2Mbit/s, but some venders have proprietary 3Mbit/s rates available.
The DSSS network standard is 802.11hr, which is officially 11Mbit/s.
In Canada/USA, the maximum power output at your antenna is +36dBm ERP (Effective Radiated Power).
In Europe, the maximum power output is only +20dBm.
In my experience to date,
FHSS systems will consistently with up to 97% signal loss, while DSSS will work up to 30-40% signal loss.
When co-existing FHSS & DSSS, the frequency hopper will run nicely 2-3Mbit, while the direct sequence radio will drop from 11Mbit to 1Mbit with 50% "interference".
My longest Links to date(FHSS):
.....13.2km @ 1Mbit/s
.....10.1km @ 2Mbit/s
.....6.7km @ 3Mbit/s
If anyone else has longest link or interference stats, please post them.
Yup, that's right. A microwave oven is, depending on manufacturing tolerances, usually designed to be a big (500W+) radio transmitter running at 2.450GHz.
Now, all the energy coming from the magnetron's antenna *should* be staying in the cavity, but especially near the door seals and the diffraction gratings (ie. the "grille" on the window), you're probably going to be getting some noise radiated.
Since a microwave oven uses RF power to produce heat, it doesn't need to modulate a carrier. Nor does it need to be too precise, and, frankly, they aren't.
Now, your home networking equipment, cordless phones and stuff run in a band that is *unlicensed* for a reason: a 500 watt microwave oven, releasing anywhere under 5mW per cm^2 (the accepted safe limit) of energy, can still be releasing 5-10 watts of RF power over the total area of the cavity.
This will drown out other radio signals in the band, and is therefore the reason *why* this band is left as a "general purpose", unlicensed band. You can't force someone to get a radio transmitter license for the microwave oven they bought in 1978.
Your wireless ethernet setup probably puts out somewhere in the range of 50-100mW of transmitter power per node. That will be drowned out by the RF hash coming off a microwave about as effectively as a flutist in the audience of an AC/DC concert.
The good thing is, though, signals in this frequency range are very directional, and in many ways behave like light. They pass through things that light won't pass through, but, on the other hand, they travel in straight lines and are easily reflected. And if you're in a concrete or steel building - like any apartment or something like that - the RF from either the microwave ovens or the wireless LAN - will not propagate very well.
Microwave frequencies are basically unsuitable for anything but cooking appliances and line-of-sight applications (microwave TV and data relays, radar, satellite up/down links, etc.). It's only because the spectrum is so nearly saturated that you'd want to use them. But there will always be drawbacks as we enter the higher frequencies. Don't expect much, it's not possible.
Fire and Meat. Yummy.
Hmm. It it's so bad that stuff like stoves can go crazy, what happens to people with bionic ears and pacemakers?
My wife has a cochlear implant. So far the only electromagnetic interference with the device we know of is the anti-theft scanners at the doors of stores, which create an annoying but tolerable buzzing for her.
Ooh, a sarcasm detector. Oh, that's a real useful invention.
In the RC days, you had to select frequency by crystal selection.
The license free devices have similar ways to get their data sent - they do frequency hopping, direct sequence, etc. Please read the other replies about this.
The old RC gear at one frequency is just not a valid comparison to modern 2.4GHz devices.
-- From Denmark
2.4GHz? Hmmm, and microwave cookers use 2.45GHz. Imagine having a whacking great free-running oscillator, drifting with temperature, right next door to your ethernet...
Any spec on what happens to your network when you nuke your coffee? Cheers,
Gordonjcp
I see you didn't take my advice. Grow a clue and either follow my advice or read up on the technical details. I've seen this happen with my own eyes and at a later stage was also able to explain what happened due to my technical studies.
Yes but you dont need to induce the power into the enginge. Mess up the controls and you could get a freghttrain to run amok. It has been done with planes ( cellphones, you know the rest )
You shouldent underestimate the strangeness of things that can happen when dealing with HFEM radiation.
This is my sig, show me yours
Umm, aren't most lightbulbs 50 - 100 W?
Riiiiiiight. Seen any funny lights in the sky lately?
I just have to put my old nokia 8110 next to my Sun ultra1 to witness some really flaky stuff. And since I am taking an astronomy class This summer: Yes I have seen some funny lights in the sky lately, A couple of kvasars and an close flyby of an small asteroid, anything else?
Wenn I said controls I ment control system or electronics or whatever you want to call it.
In A modern train by ABB all the redundant electronic subsustems (ALL) are bit-inverted from their counterparts so that they wont suffer the same from interference.
I used to work at an small airport here in sweden when one of the pilots told me an amusing story of a buissniesman who when he rebooted his laptop made the autopilot turn. No wavelan and no GSM was involved.
This is my sig, show me yours
GSM @ 1900 MHz
CDMA @ 1900 MHz
TDMA @ 1900 MHz
I have a GSM phone, and I have friends with CDMA and TDMA phones, all at the same frequency. We can be in a room together and I notice no interference, although the only real difference between the phones is their software/protocol/codec.
So, do thew rules change at 2400 MHz? Do devices interfere just because they're at the same frequency? Are sloppy codecs involved? Are the protocols messy?
Questions, questions, questions...
Actually all frequencies can interfere and resonate with your various body parts. It has being established that in experiments with rats and mice frequencies on which US cell phones operate cause the rodents to develop disorientation and worsens their further learning abilities. Of-course rats and mice are not people but in some respect mice are the closest human cousines, they have the DNA closest to the humans (after the primates of-course). So it's not only your wireless network that is suffering, it could well be your wireless brain too.
You can't handle the truth.
http://www.wirelessethernet.org/
'nuf said.
-- From Denmark
After more research they discovered that the 'radiation' did indeed affect the human brain and were also capable of reproducing this phenomenon by subjecting people to a certain amount of "radiation" which was created by high voltage electrical coils.
I don't have an url anymore since this research happened allready some time ago but I'm quite sure that anyone capable of using a search engine should be able to track this down again.
btw; out of curiousity, you wouldn't happen to work for some GSM network provider?
I'm from Holland and like in every country we also got out television and radio stations, next to a line up of GSM networks. All of these have transmitters. The GSM's have small antenna's which are spreak among the country but the television and radio have one big antenna which allmost covers the entire country. And here the fun part begins.... People living there are having extremely difficult times in buying electrical equipment. Why? Because it hardly works and or acts extremely funny. And I'm not talking about weirdness like we all know from Windows. No; this is serious stuff. Like electronic stoves going crazy (hot / cold), microwaves which act crazy or not at all for no reason what so ever, electric trains which run out of their own; a copper wire is more then efficient. Things are so bad that most people just can't use any electrical devices such as computers; they don't work as it should. Things are so extreme that local re-sellers are refusing to sell these people electrical equipment since they keep claiming due to problems.
So basicly this article doesn't come as a surprise to me. There is more going on then people know, and all the radio waves out there are doing something. IMHO even more then most people realize.
I chose an ad hoc configuration, so there was no problem; the non-pro version of the driver should work to connect windows to Linux (in fact I'm using the standard aviator driver on one of my home machines, and the raytheon version of the pro driver -- for the same card. The only difference is the pro driver supports communication to access points used to bridge the wireless network to the ethernet. Instead, I created a separate subnet and use the Linux box as a router. You could, i guess, bridge if you wanted to set it up in your Linux kernel. I haven't tried it.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
SOL = Shit Outta Luck love, br4dh4x0r
I honestly think that high frequency device communications will only develop well, without government interference. Once all of the protocols and devices have been developed thourohghly, then let the FCC or whomever take over. Interference of radio waves or interference of capitalistic government. Thats what I thought.
Pax Digitalia
Do you mean "across the speaker terminals" ?
I would guess that the right place to put a capacitor is at the input of the speaker amplifier - so that the first stage in the amplifier does not receive any RF to rectify (and then amplify).
73 de oz1nkj
-- From Denmark
I install 802.11 networks by Symbol, Lucent and Telxon (Aironet/Cisco) and this is something I come into contact with more and more.
Frequency Hopping (FH) devices tend to kill the reception by Direct Sequence (DS) devices, mainly due to the differences in signal strength. Multiple DS networks can happily coexist, and run at 1,2,5,11 or 25 MBit/s while keeping the actual signal at below ambient noise strength (nice - security-wise)
FH networks just tend to upset all other 802.11 networks, and they only go up to 2 Mbit/s at the moment. The reason people use them is that they are very stable and solid. They just work, without tweaking!
With todays bandwidth demands, you have to go for the 25 Mbit/s gear (which gives you throughput roughly equivalent to a 40Mbit/s ethernet type protocol - due to use of CSMA/CA not CSMA/CD) so things should get better as more people use DS not FH:)
Frog51
Frog51
With these sorts of things, if you want to have clean unobstructed use of a band you've got to stay ahead of the rest of the world. Thats means upgrading to the expensive 5.7Ghz band.
Not only does 2.4Ghz have problems with exploding individual use (phones, networks, etc..) but because the band is 'free' (not as in speech, but as in bulk email) businesses have taken it apon themselves to try to use every last bit of it.
Ricochet is an internet acessess company primaraly in the bay area but spreading to other metro areas around the country. Their plan calls for putting poletop boxes every half mile or so; they have already done this with 900Mhz and are deploying 2.4Ghz. You can imagine what sort of bite this takes out of the useable bandwidth of a frequency.
Other companies are deploying 'wireless T1's also, using this frequency. On top of that alot of home users are buying 2.4Ghz network equipment to save themselves from running ethernet throughout their house. The prevailance of this equipment is being fueled by its recently lowered costs and the emergence of the 802.11 standard for interoperability of devices. 2.4Ghz is getting pretty noisy.
I finnally threw my hands up, moved out of the mountains and got DSL. I now enjoy 66% uptime from wonderful PacBell DSL (but thats another rant entirely).
So put out the bread for 5.7Ghz radios or accept the fact that interference is only going to get worse.
-- Greg
Slashdot, would a spell-checker for posting be too much to ask? It's not rocket science!
I'm really mystified by the cause, I'd appreciate anybody who know what the 'cause is because I really do worry about my brain getting fried by these things.
Go here for more info.
Just like breast implants causing systemic problems, this has been effectively debunked. I'd like a pointer to any valid studies that you know about that actually shows cell phones cause brain tumors. Sure there can be "links" between cell phone use and brain tumors, but I'll bet you that the study participants eat a lot of red meat also. Wonder if they smoke, or drink also. Just like the detrimental effects of living next to or under an ultra high power electric line (such as that coming from a nuclear power plant) were blown out of proportion so are the effects of 2.4GHz network equipment.
There's another issue here besides frequency hopping and spread spectrum. While wireless ethernet is not exactly the same protocol as wired ethernet, it does share one significant property: if there's a transmission failure, it backs off and retries. The amount of time between retries increases randomly but exponentially. Why? On a wired network, it's to prevent two machines sending colliding packets from trying again at the same time (and colliding again). If you're using a wireless spectrum that only has other wireless ethernet users on it, the same holds true. Unfortunately, if you have other users of the spectrum that don't play by these rules, ethernet gets screwed, since it backs off politely while the other user (like telephones) just continue to blast data on through. Since the other never backs off, ethernet continues to wait longer and longer for an interference-free window.
Well, he gives us the answer in his article. ... well, one can understand why there's just not enough of the bandwidth left. Just like with the 900MHz range, 2.4GHz is in the ISM band (Industry, Science, and Medical), the two options at this point are: change the 802.11b devices to 5.7GHz devices, or stick with 900MHz for the appliances to free up the 2.4 for the NICs.
In the 802.11b (the b is important) standard, he's using DSSS (Direct Sequence Spread Spectrum) radios as opposed to frequency hopping. This means he's able to get up to 11Mbps per device, but, it also means only 3 non-overlapping channels. While there are many channels (11 or 12, IIRC) in the 2.4GHz range, the DSSS 11Mbps radios lump multiple channels together (802.11 radios were 2Mbps because they only used one channel instead of groups of channels). Now, toss the Seimens Gigaset (which is also Spread Spectrum, I believe) and other wireless devices into the mix and
Just my thoughts.
3 Com are currently running a deal (in the UK, anyway - probably is similar in US) for 2Mbit/s Access Point and 3 ISA or PCMCIA cards for £800. Translate to US - translate to $ (usually works that way!) means a happy home WLAN for $800. Their kit is rebadged Symbol FH gear
I have run Quake 2 over an 11Mbit DS Aironet WLAN with 4 players and it was as good as my ethernet, even though one of the guys was a couple of km away (directional antenna for him)
If you are grabbing vast database files then it won't be happy, but it copes with most home user stuff:)
Frog51
Frog51
Ofcourse this is expected to cause problems... What's concerning me is, as the article proposes, that the manufacturers do not seem concerned about this. In the old days when You bought an open fequency "commodity" (anything really), You could usually "tune" the set to a slightly lower or higher fequency (as You changed Your crystals). This option seems to be gone from most equipment You buy today. I tested a Wireless Video/Audio transmitter set, and it only had TWO settings for frequencies ! Suppose both my neighbors had the same set ? And on most wireless phones and LANs there's only ONE preset frequency, and since it's neatly set at EXACTLY 2.4 GHz, ofcourse they'll interfere... So what are we supposed to do ? Shield the transmitter and reciever in a cage ? Might as well go back to wires then.
No this is DEFINATELY up to the manufacturers to work out. if they want to sell their crap to us. They better make sure it works.
If you have any combination of cordless phones, wireless ethernet, wireless video, or Bluetooth you could be having problems. Not only will your bank balance will be suffering a from the debhilitating effects of continuous expenditure on unecessary geeky networking technologies, but your health will be in sever danger.
An article to be published in the Lancet later this month will show how people can suffer serious side effects from replacing all the cables in their house.
"It started happening after I went to one of those underground Linux install parties" reports a young man, who we'll call 'Alf'.
"At first, it was just phones. You know, people passing around some Nokia's and Ericssons, and it felt really good to be cordless. It was like I was with the in-crowd."
"After a few weeks though, people started getting out the infra-red enabled PDAs out. I didn't think anything of it at the time."
But, as the report shows, cordlessness is an unpleasant and addictive activity, and it's only a matter of time before the serious health implications start. 'Ben' has been in re-hab for three months now, getting used to staying in the same place when he talks on the phone, and being re-trained in Cat5 cabling.
"I can't remember much towards the end" says Ben, "I was really out of it. There was like about 4 of us in this house in Shoreditch, you know with serious 802.11b right through. It was like a permanent trip. We used to have these wild parties at weekends with loads of girls and booze, it was pretty wild, people doing it with like Psion5's and i-mode phones, really f**cked up stuff."
But although Ben is recovering, it's a growing problem thoughout London and the whole of the West. Dissatisfied with their parents' strict ideas of free love, home grown dope, and long skirts, the young generation are turning to hardcore wireless technologies, with street names such as Bluetooth, WAP and i-mode.
Next: The Goverment launches "War on Wireless" to stop this disturbing trend in our young people.
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- ETS 300 328
- ETS 300 826
The later standard is used for Bluetooth applications; from what I understand all equipment must abide to ETS 3090 328.The fact that the Siemens Gigaset and X10 are noisy could be that the ETSI standards actually allows them to do prett much what they want to; it could also be the case of bad design of the X10 or Gigaset equipment. I have seen plenty of cases where equipment from wellknown manufacturers claims to be approved according to CE emissions standards (EN55022/23), but when measured up proves to be way of.
Regarding Bluetooth, it is my understanding (after working with it for one year from a hardware designer perspective) that BT is designed to work in "noisy" environments. BTs frequency jumping scheme is designed to make the most of the frequency band, even if there are cordless phones and wireless LANs using the spectrum also.
Also, BT is a low power technique in contrast to IEE802.11 and possibly the cordless telephones.
I have followed some threads regarding possible interference between IEEE802.11 and BT, and the latest information is that they do not interfere and thus can coexist.
Standard disclaimer: I may be wrong
The author of the linked article is obviously inadept at grasping the reality of what he was witnessing.
The 802.11 cards and Siemens phone system are frequency-hopping. By switching frequencies often, they reduce overall interference at the expense of a little bandwidth (there's plenty of room at 2.4GHz for these things to co-exist). Some types of frequency-hopping "spread spectrum" devices will dynamically learn trouble-spots and avoid them, bringing bandwidth back up to a point approaching ideal (unless that entire block of spectrum is completely hosed).
So, the phone system and wirelss LAN should work fine together. There will be a slight (measurable, but imperceptable) decrease in bandwidth for the LAN while phones are in use. The phones, if they're poorly designed and/or the CODEC is intolerant of errors, may suffer an occasional (and very brief) dropouts; due to the real-time streamed nature of the device, retransmissions aren't possible as they are with 802.11. I don't suspect these dropouts would be overly bothersome, or even noticable in most instances.
Interestingly, the X10 video-sender box was the last thing he threw away. Oddly enough, that's the device which should have gone away *first*. It's cheap - too cheap to use any of the present-day bandwidth-reducing digital coolness of most other 2.4GHz devices. So, it spews forth broadband analog video - likely using *more* bandwidth than a TV station to avoid expensive modulation/demodulation parts - destroying the 2.4GHz for the rest of the household toys. Remember the remark above about the spectrum being completely hosed? This is probably a better example of an RF monster than anything else available to a consumer today.
Had he turned off the bargain-bin X10 stuff first, I strongly suspect he would have had no further difficulty (and would continue to enjoy the hideously-cool phone system).
That all said, I really don't see the need for moving to 2.4GHZ for *everything*. It offers more bandwidth for a given slice of spectrum, which is nice - and really not needed for things like telephones. I prefer to get my cancer from tobacco, standing too close to the microwave, and hanging out by 600,000 volt transmission lines - not talking on the phone.
Kid-proof tablet..
I think he means that interference from the high power RF is playing hell with anything computer controlled. What device these days doesn't have some type of silicon chip? From your wristwatch to the controls of a real electric train, IC's don't handle ionizing radiation and RF very well. Some CMOS chips are so sensitive they can be burned out by just handling them improperly. If everything had proper shielding this would be a non issue.
About the light bulbs, the two wires act like an antenna and pick up RF. People used that method to tune their transmitters, adjust it for the brightest light.
Only the State obtains its revenue by coercion. - Murray Rothbard
I have to read slashdot during the night if I want to be among the first to see the articles and I'm lucky if I get second last post if I visit slashdot during the day.
So how about having people in other continents posting stories too.
Look at my other post about interference and computer controls. There is still a lot we don't know about radiation and electricity. Ball lightning is a good example, its existence is documented, but not explained.
Only the State obtains its revenue by coercion. - Murray Rothbard
I recently bought a siemens gigaset, however I have this terrible problem with a loud oscilating ring and echo noise. I was wondering what kind of interference could create an _echo_? I thought it was rather strange... I should try to turn off our microwave see if that helps.. but its built into the house so that's easier said then done.. it means flipping the circuit breaker for 1/2 the kitchen...
Thats a myth. When too many people listen to one radio station does the reception suffer because they are absorbing all the power? I think not. The power is distributed in all directions and one person can't "suck" in more than the next. Its completely passive and absorbed equally all over. Nikola Tesla had plans for distributing power in that manner, because an unlimited number of receivers are possible.
Only the State obtains its revenue by coercion. - Murray Rothbard
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frequency ----->
Hint: Use the <tt> tag.
Here's a fixed version of the chart. I hopt that this is enough text to pass the lameness filter. Isn't that lame -- having to add lame text to bypass the lameness filter.
Anomalous: inconsistent with or deviating from what is usual, normal, or expected
Anomalous: deviating from what is usual, normal, or expected
Canard: a false or unfounded repor
These problems are no different than when you go to Radio Shack and buy some of their radio controlled toys. The toys are plainly marked what frequency they run on. If you get two cars that are on the same frequency and try to run them at the same time, of course they are gonna go wacky!
We are going to see more and more devices up at 2.4 GHz. What is the solution? Quit it! It is that simple.
These same problems everyone is gritching about is how it was with the early 49 MHz phones. Someone would get one then their neighbor would get one and they would inevitably take them back to the store because "they were broken". Well, sorry, but they are not broken, it is just that someone else is on that frequency also.
Look around your house and check out how many wireless devices you have. Do you need 3 cordless phones? Do you need wireless TV transmitters and ethernet cards too? Yeah, they are nice, but when you start getting interference between them, well, I hate to say it, but there is only one person you can blame for it.
I've noticed that when my microwave is on, my
WaveLan latency goes way up. I guess I have
a nice 2.4Gz microwave.
I don't know whether I'm remembering this correctly, but don't microwave ovens cook using some in the 2.4 GHz range? Given, they should be sufficently shielded, though who is really going trust their frag count to should. I guess I'll have to make a sign that says "No Microwave use, Quake match in progress..."