[mcdonaldREMOVE TO ACTUALLY REACH [email protected]]

codifus wrote:


1. Grab the signal from the air in as accurate method as possible,
rejecting all other signals.
2. Extract the audio from the carrier wave.

Digital synthesizer tuners do part 1 very well, and cheaply. To
achieve part 2 very well, a manufacturer has to resort relatively
expensive design circuitry.

Uh, not really. To extract the the audio, today one does the following:

1) convert the signal to some intermediate frequency

2) amplify to just below the point of limiting, with a modest
bandwidth filter that drop off steeply only well outside
the channel of interest (but steeply enough that 2nd adjacent
channel signal does not cause terrible overload).

3) digitize the signal at an adequate number of bits at some
submultiple of the IF frequency, sufficient to prevent
aliasing due to the fringe of the IF frequency filter.

4) calculate what the signal is as audio

Note that if the ADC is good enough (and today they are really,
really good enough) part 3) is not a serious limit to
performance, and part 4) is absolutely perfect.

Thus the RF stages and the analog IF filter become the tuner's
limiting factor. The real limit is the quality of the incoming signal.

and parts 3) and 4) are cheap as the sand they are made from.

Doug McDonald