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[Discuss-gnuradio] A newbie question

From: Bill Wetzel
Subject: [Discuss-gnuradio] A newbie question
Date: Sun, 07 Apr 2002 14:27:31 -0400


I have been fascinated with the ideas soft-radio for quite a few
years but have been bothered by one detail - saturation.  The 
dynamic range of any reasonable ADC looks much to small to accommodate
the range in signal strengths actually seen at the antenna.  In conventional
analog receivers saturation is prevented in downstream stages by analog
filtering in upstream stages to remove a powerful station that would otherwise
block a weak station.  In a soft-radio, however, all stations are present
in the signal at the time of a->d conversion. The converter must have
sufficient resolution to encode not only the powerful signals but the weakest
one of interest with enough bits to provide reasonable fidelity.

Given the dynamic range of actual signals that I have observed with a 
spectrum analyzer I don't understand how they can be coded with adequate
resolution using coders that are affordable to the average hobbyiest or
that would be practical in consumer electronics.  Are log-coders 
used - something similar to mu-law coders that are used for audio?
How wide are the coders?  How much do they cost?

Would someone say a few words on the point, please?


Bill Wetzel                             address@hidden
615 Little Silver Point Road    http://www.faradic.net/~billw
Little Silver, NJ 07739         732-530-1128

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