Here links to articles about the basics of a Software Define Radio will be placed. A nice beginning are some of the articles is the link below.

In particular the "A Software Defined Radio for the Masses" articles by Gerald Youngblood found towards the bottom of the page. http://www.arrl.org/tis/info/sdr.html

Articles how Quadrature signals work. http://www.dspguru.com/info/tutor/quadsig.htm

A free book on how DSP works, an excellent book. http://www.dspguide.com/

Articles on DSP http://www.doug-smith.net/downloads.htm

Work in progress, check back often.