Some of you who are not subscribers to QRP-L might have missed a
very interesting discussion about quadrature sampling.
Frank AB2KT starts it off with a very challenging description
http://mailman.qth.net/pipermail/qrp-l/20050828/026178.html
and refers to
http://lists.gnu.org/archive/html/discuss-gnuradio/2003-01/msg00137.html
I will let you follow the threads yourself.
QRP-L archives are always visible here
http://mailman.qth.net/pipermail/qrp-l/
and GNURadio discussions here
http://lists.gnu.org/archive/html/discuss-gnuradio/
de Ken