Jeff Liebermann wrote:
(snip)

> I'll skip all the intermediate modulation schemes and jump directly to
> the present. Microprocessors have become so cheap, that it's now
> economical to do DSP (digital signal processing) in every radio.
> Digital has the huge advantage of offering error correction, noise
> immunity, bandwidth compression, and high spectral efficiency. Schemes
> have been devised that will extract useful audio or data from signals
> that are well below the thermal noise floor. You can't do that with
> AM (or FM). If you attempted to do Wi-Fi using pure AM technology,
> the data thruput would be horrible and/or the error rate would be
> hideous.

Somehow this reminds me that there have been discussions on
using digital techniques to demodulate standard AM and FM radio
signals. Now that we have digital radio, what seems to be
called HD radio (radio stations seem to advertise it pretty often).

http://en.wikipedia.org/wiki/HD_Radio

I don't remember much discussion here about it.

-- glen