[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



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