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External Radio Noise Sources

June 5th Fact-of-the-Day

Radio receivers tuned to any frequency used for communication are subject to interference from one of more of the following external noise sources: 1) man-made interference from electrical and electronic devices of many kinds; 2) terrestrial atmospheric noise from lightning storms; 3) cosmic radiation from space. Desired signals must be significantly stronger than the sum of those noises to be clearly understandable. Man-made noise often can be filtered at its source or a receiving antenna can be physically separated from a noise source. Where man-made noise has been reduced to insignificance, cosmic noise tends to predominate above 15 MHz and terrestrial noise tends to predominate below that frequency. Both terrestrial and cosmic noise can be minimized by using directional receiving antennas. However, antennas with narrow beam-widths are huge in size at low frequencies which limits their practicality in many applications. ©2005 Martek International All rights reserved.


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