[AMRadio] Occupied vs Necessary Bandwidth |
Donald Chester
k4kyv at hotmail.com
Sun Jan 15 19:53:28 EST 2006
Occupied vs Necessary bandwidth With the ARRL bandwidth petition, the terms "occupied" and "necessary" bandwidth have come to light. Our comments to the FCC will be taken more seriously if we leave the impression that we know what we are talking about. Specifically, we should know exactly what is meant by the terms "occupied" and "necessary" bandwidth. The current set of definitions of the spectral properties of transmitter emissions,"necessary bandwidth," " occupied bandwidth," plus "out-of-band emission," " spurious emission," etc. contained in Article 1, Section VI, of the Radio Regulations came into being through the work of the World Administrative Radio Conference in Geneva, 1979. "Necessary bandwidth" is the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions for a given class of emission. "Occupied bandwidth" is the width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to 0.5% of the emitted power. This is also known as the 99% emission bandwidth. For further information, view the following websites: Terminology: “channel bandwidth” is defined in conjunction with the terms “occupied bandwidth” and “necessary bandwidth” that are defined by ITU Radio Regulations S1.153 (occupied bandwidth) and S1.152 (necessary bandwidth), as follows: "Occupied bandwidth: The width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to a specified percentage B /2 of the total mean power of a given emission. Unless otherwise specified by the CCIR for the appropriate class of emission, the value of B /2 should be taken as 0.5%. "Note 1: The percentage of the total power outside the occupied bandwidth is represented by B. "Note 2: In some cases, e.g., multichannel frequency-division multiplexing systems, use of the 0.5% limits may lead to certain difficulties in the practical application of the definition of occupied and necessary bandwidth; in such cases, a different percentage may prove useful.“ "Necessary bandwidth: For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions." grouper.ieee.org/groups/802/20/Contribs/C802.20-04-11r1c.doc (copy & paste into your browser, then download the Word document) "Necessary bandwidth: For a given class of emission, the minimum value of the occupied bandwidth sufficient to ensure the transmission of information at the rate and with the quality required for the system employed, under specified conditions. Emissions useful for the good functioning of the receiving equipment as, for example, the emission corresponding to the carrier systems, shall be included in the necessary bandwidth." http://wireless.fcc.gov/services/ind&bus/licensing/bandwidth.html "Occupied bandwidth: "1. The width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to a specified percentage B /2 of the total mean power of a given emission. Unless otherwise specified by the CCIR for the appropriate class of emission, the value of B /2 should be taken as 0.5%. [NTIA] [RR] Note 1: The percentage of the total power outside the occupied bandwidth is represented by B. Note 2: In some cases, e.g., multichannel frequency-division multiplexing systems, use of the 0.5% limits may lead to certain difficulties in the practical application of the definition of occupied and necessary bandwidth; in such cases, a different percentage may prove useful. "2. The frequency bandwidth such that, below its lower and above its upper frequency limits, the mean powers radiated are each equal to 0.5% of the total mean power radiated by a given emission. [47CFR]" http://www.atis.org/tg2k/_occupied_bandwidth.html Check out some of these sites at: http://www.google.com/search?q=necessary+bandwidth,+occupied+bandwidth,+necessary+bandwidth&hl=en&lr=lang_en|lang_fr&client=firefox-a&rls=org.mozilla:en-US:official&start=0&sa=N _______________________________________________________________ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
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