Noise (radio) 3339042 218205189 2008-06-09T17:02:44Z Peaceoutside 4364643 [[WP:UNDO|Undid]] revision 217097140 by [[Special:Contributions/81.156.196.237|81.156.196.237]] ([[User talk:81.156.196.237|talk]]) '''Radio noise''' in radio reception is the superposition of [[white noise]] (also called "static") and other disturbing influences on the signal, caused either by [[thermal noise]] and other [[electronic noise]] from receiver input circuits or by interference from radiated electromagnetic noise picked up by the receiver's [[antenna (radio)|antenna]]. If no noise was picked up with radio signals, even weak transmissions could be received at virtually any distance by making a radio receiver that was sensitive enough. In practice this doesn't work, and a point is reached where the only way to extend the range of a transmission is to increase the transmitter power. Thermal noise can be made lower by cooling the circuits, but this is only usually worthwhile on [[radio telescope]]s. In other applications the limiting noise source depends on the frequency range in use. At [[low frequency|low freqencies]] ([[longwave]] or [[mediumwave]]) and at [[high frequency|high frequencies]] ([[shortwave]]), interference caused by [[lightning]] or by nearby electrical impulses in [[switch|electrical switches]], [[electric motor|motors]], vehicle [[ignition system|ignition circuits]], [[computer]]s, and other man-made sources tends to swamp transmissions with thermal noise. These noises are often referred to as [[static]]. [[Atmospheric noise]] is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms. At [[very high frequency]] and [[ultra high frequency]] these sources can still be important, but at a much lower level, such that thermal noise is usually the limiting factor. In the microwave region, [[cosmic noise|cosmic background noise]] may be relevant. <p>Electromagnetic noise can interfere with electronic equipment in general, causing malfunction, and in recent years standards have been laid down for the levels of [[electromagnetic radiation]] that electronic equipment is permitted to radiate. These standards are aimed at ensuring what is referred to as [[electromagnetic compatibility]], or EMC. == See also == *[[Noise]] *[[Signal noise]] == Further information == === Noise statistics === * [http://www.itu.int/rec/R-REC-P.372/en Radio noise]. ITU-R Recommendation P.372, [[International Telecommunication Union]], Geneva. * Blackard, K.L.; et al.: [http://dx.doi.org/10.1109/49.233212 Measurements and models of radio frequency impulsive noise for indoor wireless communications]. IEEE Journal on Selected Areas in Communications 11 (7), September 1993. * Dalke, R.; et al.: [http://dx.doi.org/10.1109/WCC.1997.622284 Measurement and analysis of man-made noise in VHF and UHF bands]. Wireless Communications Conference, 1997. * Lauber, W.R.; Bertrand, J.M.: [http://dx.doi.org/10.1109/15.784164 Statistics of motor vehicle ignition noise at VHF/UHF]. IEEE Transactions on Electromagnetic Compatibility 41 (3), August 1999. * Sanchez, M.G.; et al.: [http://dx.doi.org/10.1109/15.765101 Impulsive noise measurements and characterization in a UHF digitalTV channel]. IEEE Transactions on Electromagnetic Compatibility 41 (2), May 1999. * Blankenship, T.K.; Rappaport, T.S.: [http://dx.doi.org/10.1109/8.660963 Characteristics of impulsive noise in the 450-MHz band in hospitals and clinics]. IEEE Transactions on Antennas and Propagation 46 (2), February 1998. [[Category:Noise|Radio]]