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Decibels and Logarithms

February 6th Fact-of-the-Day

Most people seriously interested in technical aspects of radio know that a decibel is one-tenth of an Alexander Graham Bell 'Bell' unit, which is the logarithm of the ratio of two power levels, and that decibels therefore are logarithmically related to power ratios. Many who routinely use decibels (signal strength S9+35, gain flat to within 3dB, etc.) probably assume they are using a relatively modern method of expressing large ratios -- at least, a method used only since the time of Bell. If so, they are wrong. Old Babylonian tablets contain tables that are exactly analogous to modern tables of antilogarithms. Logarithmic tables that list the first ten powers for various bases also have been found. A student examination on a Babylonian tablet asks 'What is the logarithm of the given number in a system with the certain number as a base?' ©2005 Martek International All rights reserved.


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