PS: Seems your idea wasn't that far off the mark after all:
http://www.universal-radio.com/catal...rxvr/0014.html
That thing converts the whole 0-30 MHz range to digital with a sample
rate of 66.67 MHz and a 14 bit resolution (dynamic range ~84 dB). You
can then grab approx. 160 kHz wide pieces from the spectrum and send
them to the PC for analysis (including demodulation in whatever mode)
via USB. Spectrum analysis is the primary target application for the
thing, which sounds reasonable since the dynamic range wouldn't be
suitable for a DX rig. I guess things would become yet more interesting
with a USB 2.0 or Firewire interface, which would allow up to 20 times
wider spectral windows.

I assume that in several years it'll be possible to sample the whole
0-30 MHz range with 16, later with 18 and yet later with 20 bits, at
which point a full-featured communications receiver covering signals
from .1 µV to 100 mV should be possible. Distortion, however, will
probably be a matter for itself. I bet the strong signal handling of
good pro rigs will not be reached by direct-A/D based receivers any time
soon. But interesting niche solutions they are for sure...

Stephan
--
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