Re: [IRCA] IBOC power

["Chuck Hutton" <charlesh3@xxxxxxx>]

Not really. The AM part of QAM tells you that AM is part of the equation.
With xxQAM (in the case of IBOC, 16QAM), there are two axes used in the
modulation: phase and amplitude.

By the way, the AM part of the QAM is what is responsible for part of the
bandwidth inefficiency of IBOC: in order to keep it from being even louder
than it already is with an envelope detector, 4 of the 6 digital sidebands
are what are called "complex conjugates". In simple words, this means that
the sidebands see-saw: if the upper tertiary sideband is transmitting an
amplitude of x+y then the lower tertiary sideband transmits x-y. As a
result, the envelope is constant and nothing is detected.


I tried to keep this short. I can hear the snoring.


Chuck


On Friday 23 September 2005 17:53, Dan Strassberg wrote:

<CLIP
I believe that QAM (like FM) is a form of modulation in which the sideband
power is constant (and therefore always maximum). If anything I've said
in this message is incorrect, please set me straight.

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