I'd like to have more information about solutions to block RFI. Like info on the VCC filter and decoupling. --Toric 07:41, 26 Feb 2005 (UTC)
- 1 how to add simplest Electromagnetic shield
- 2 Electromagnetic interference
- 3 Requested move
- 4 Interference vs. interference
- 5 Radiated Spurious Emissions and 2nd Harmonics
- 6 Removal of redundant and unsourced additions
- 7 Scope of article
- 8 Problematic last sentence in the first section
- 9 satallite and microwave link interferance
- 10 Commercial Links
- 11 EMI Manufacturers ... WTF?
how to add simplest Electromagnetic shield
A simple conductor mesh connected to the ckt gnd will do or we have to do more for the shielding. u can send me replies on firstname.lastname@example.org
Electromagnetic interference redirects here, but it seems like radio frequency interference is a type of electromagnetic interference. -- Kjkolb 01:13, 7 January 2006 (UTC)
Interference vs. interference
- rv: interesting article, but it's only one guy's POV, and he's a network engineer, not RF; he's confusing interference (wave superposition) with interference (bad stuff)
What causes interference (bad stuff) other than interference (wave superposition)? If a receiver is selective enough to pick apart two superposed signals, then is the other signal really interference (bad stuff)? --Damian Yerrick (talk | stalk) 03:17, 9 April 2007 (UTC)
- Yes, it is. Consider a conventional AM radio channel with carrier frequency F and bandwidth B. The receiver has to have bandwidth B in order to receive the signal. In other words, it has to receive all frequencies from F-B/2 to F+B/2. If I then switch on a device that emits EM waves at frequency F+B/4, say, then that emission will be within the band of the receiver and, if it is powerful enough, will cause interference. This might manifest itself as a whine added to the audio output or, worse, it might overload the receiver and cause it to go nonlinear, blocking the wanted signal entirely. This is more serious than just the superposition of waves. Reed seems to be implying, although he surely knows better, that all radio signals have zero bandwidth. His digression about the interference of photons is a straw man. Nobody, not even the FCC, thinks that radio sources interfere with each other because their photons are competing for space.
- David P. Reed is a proponent of ultra-wideband (UWB) radio. This is technically a great idea, with the potential to squeeze much more bandwidth out of the RF spectrum than we get with conventional technologies, but it has just one tiny flaw. It involves taking over the entire RF spectrum so that all non-UWB (what he calls 'dumb') devices won't work any more. The regulators are a little bit reluctant to hand over the entire spectrum to Reed and his colleagues, and Reed never stops complaining about this. When you read his articles, you have to ask yourself where his interest lies: is it in delivering accurate information, or is it in campaigning for his favourite technology? He may genuinely think that he is doing mankind a favour, and perhaps if the whole world goes UWB then he may be proved right, but he is being a bit selective with the truth in order to promote his view. There may be a way to express this issue in NPOV terms for Wikipedia, but that isn't going to happen if we just quote Reed verbatim. --Heron 11:09, 9 April 2007 (UTC)
- I wasn't quoting Reed verbatim, just stating my own understanding in the subject in my own words. In your case of AM radio, there are ways to improve the selectivity of the receiver. Can't it tune out a lot of the whine from the F+B/4 source by rotating the loop antenna? Or can't it notch out the F+B/4 and use the lower sideband to error-correct the upper sideband? --Damian Yerrick (talk | stalk) 21:29, 9 April 2007 (UTC)
- Sorry, I didn't mean to be insulting with the 'verbatim' thing. I like the idea about using one sideband to correct the other one, but you are getting into complex signal processing territory, which is exactly where we don't to be. The point is that there are billions of 'dumb' radio devices, and other types of devices like speaker cables, that are susceptible to RFI and won't work if UWB is given free rein. Yes, those devices could be redesigned, but who is going to pay for that? If UWB isn't properly regulated then life is going to get more expensive because of all the extra filtering and shielding that 'dumb' devices will need. Anyway, that's just futurology at this stage. Meanwhile, we have to speak the truth. This means not pretending that interference doesn't exist just because there is one class of devices that doesn't care about it. Thank you for listening. :-) --Heron 22:03, 10 April 2007 (UTC)
- Why don't we want to be in complex signal processing territory? After a point, there is more gain from more efficient use of bandwidth than loss from more complex receivers. Look at XM and Sirius satellite radio; they add complexity to the receiver to fit more channels into the small amount of bandwidth that they are allocated. As for who's paying: the people are continually paying for every year that the unselective legacy devices are not redesigned. These payments take the form of monopoly rents to the holders of exclusive spectrum licenses. And no, UWB isn't the only way to increase the selectivity of a communication system. But just to clear out misunderstood words: Do you agree that EMI can be defined as what happens when selectivity fails? --Damian Yerrick (talk | stalk) 20:07, 11 April 2007 (UTC)
- Isn't that like saying that gun murder can be defined as what happens when bulletproofing fails? I don't see the point of this redefinition game. (Well, actually, I do: it's to sell UWB.) Yes, I agree that EMI requires two participants - the transmitter and the receiver - but your definition is just pushing the blame, or at least the difficulties, to one side of the relationship, which is just as wrong as the conventional definition which pushes them to the other side. There is an interesting essay to be written about this, but it's futurology, not encyclopedia material. The truth is that bandwidth restrictions have worked fine until now, and continue to work most of the time, and 'interference' means what it says in the dictionary, not what Reed thinks it means. New technologies might make the old regime redundant in the future, but stuff that might or even should happen is not the domain of Wikipedia. --Heron 20:59, 12 April 2007 (UTC)
Radiated Spurious Emissions and 2nd Harmonics
--EXo 08:10, 23 May 2008 (UTC)
EMI is commonly attributed to the electromagnetic noise in the form of conducted or radiated electromagnetic emissions of an operating electronic device, equipment, or station that have adverse effect in the radio-frequency signal or data transmission system in use today.
However, even when not operating or powered-on, an electronic device can act as a source of EMI if it is brought close enough to a RF transmitting device. The electronic parts receive RF energy from the transmitting device, which is enough to switch-on or -off the semiconductor diodes or any die with P-N junction at a very brief period of time with frequencies in the multiples of the transmitting frequency. Hence, this electronic device will interfere the RF transmitting device.
For example, a mobile phone is sending RF signal to a cell site or transmitting tower through the uplink channels of the local GSM900 system. Then its charger is also held near the phone during the call. The semiconductor parts are positively-biased, very briefly depending on the radiated spurious emissions or signal coming from the mobile phone. They switch-on and off at 1800MHz, 2700MHz, etc. Worse still, when GSM1800 is also used in the location the charger affects that system.
The user may not notice any difference because most chargers are designed and produced with the requirements for limited radiated spurious emissions and 2nd harmonics are met. Most products are in compliance with the RF standards set by international organizations and governments.
Removal of redundant and unsourced additions
EMI/RFI Sources. The sources of EMI/RFI can be broadly classified as Natural sources and Man-made Sources.Natural sources can be further classified into terrestrial and extra-terrestrial. The commonest example of terrestrial natural source is lightning. The effects of a lightning strike can be more benign like the familiar crackle on the radio. It can also be destructive wherein the surge currents due to lightning can result in burnout of components and total destruction of systems. Other example is Electro Static Discharge or ESD. Materials can accumulate a static charge because of friction (this phenomenon is called as the Tribo-electric Effect i.e. generation of electrical charge due to friction). It is also common for the human body to accumulate charge due to friction of the skin with clothing. When such a charged operator touches a sensitive equipment an ESD event occurs. The discharge can cause damage to the equipment. Extra-terrestrial sources can include the Sun, Radio-stars (called Pulsars) or other galactic sources. Man-Made sources can be classified as Intentional and Un-intentional sources. In case of intentional sources, the intention is to generate RF energy say for communication (e.g. mobile phone) or carrying out certain process on material (induction heaters, microwave ovens) or for medical applications (e.g. diathermy). Whilst in case of un-intentional sources, the intention is NOT to generate RF energy, but is inadvertently generated. The commonest example is a SMPS where the intention is to convert voltage from AC to DC and to keep the transformer size small. This involves up-converting the 50/60Hz AC to higher frequencies and in doing so RF energy or EMI is inadvertently generated. Other examples of unintentional sources are motor drives, thyristor converters, dc-dc converters etc. - Originally added by User:Chetankathalay.
Scope of article
The article on electromagnetic compatibility gives a much broader (and more correct) description of EMI than is discussed here. I think this arcticle should be restructured and expanded acccordingly. Any objections? -- Cheers, Steelpillow (Talk) 14:20, 28 January 2009 (UTC)
- I think electromagnetic compatibility is a very well done article. Thanks for volunteering the much needed improvements here. LuckyLouie (talk) 14:38, 28 January 2009 (UTC)
Problematic last sentence in the first section
"If EMI for electronics or astronomy is reduced so is happened to RFI. (EMI/RFI in Roumanian language, 2005 - 2009)."
I cannot make sense of this sentence or even what I assume is a reference in parentheses. Would someone fix this problem?
I'm sorry I can't do it myself (due to Adult-onset Still's disease, my daily fever creeps up with any activity, so I have to pace myself carefully) and I appreciate the hard work of the person who can and does fix it. Thanks! Geekdiva (talk) 09:51, 8 September 2009 (UTC)
The bottom half of this article had a mixture of useful commercial links with information and links to pages that are principally advertising products / companies. I have tried to impartially remove those with little information content and a more commercial bias. I can see that this could be a contentious issue, if there are any concerns, please feel free to revert, replace or get in touch.Roggg (talk) 10:27, 31 May 2012 (UTC)