[AMRadio] FCC's Definition of Bandwidth

Donald Chester k4kyv at charter.net
Fri Oct 7 14:52:10 EDT 2016

> You've hit upon the crux of all of its entirety!  Things have been put
> words at very different times by far too many disparate entities!
> None of which have been reconciled nor thoughtfully been adequately
> proofread by the mess in Washington!
> Those entities that I worked for have never found ANY cohesive pieces
> amongst anything that has CFR in its title!

> Bob - N0DGN

There are the ITU definitions, from which the national requirements are

" 1.152 necessary bandwidth: For a given class of emission, the width of the
band which is just sufficient to ensure the transmission of information at
the rate and with the
quality required under specified conditions.

1.153 occupied bandwidth: The width of a frequency band such that, below the
and above the upper frequency limits, the mean powers emitted are each equal
to a specified
percentage β/2 of the total mean power of a given emission.

Unless otherwise specified in an ITU-R Recommendation for the appropriate
class of emission, the value of β/2 should be taken as 0.5%."

The original document is here:
(you may have to copy & paste the url into your browser to make it work)
Scroll down to page 21.

Apparently, when writing Part 97, the FCC added 3 dB the wrong way from -23
dB, so it became -26 dB instead of -20 dB which would be consistent with the
ITU-RR language as stated above, and the FCC's own definitions in § 2.202.

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