In July 2011 issue of AD's Analog Dialogue I spotted this article on RF design: Differential Interfaces Improve Performance in RF Transceiver Designs.
It is about designing an I/Q receiver and a transmitter using a differential signal path instead of the more common single-ended approach. With three practical examples including calculations, this article should help the design of a differential chain for HF/VHF HAM use.
Prove me wrong, but hasn't the NE602 got differential inputs and outputs?!