http://www.amsat.org/amsat-new/eagle/EaglePedia/uploads/f/ff/Helaps_Technology_Transfer_Seminar.pdf We are attempting to implement the ultimate "HELAPS-C Polyphase" with the SDR technology at our disposal. This document was prepared by Jan King, Gordon Hardman, and Karl Meinzer and contains lots of useful information. Bob N4HY