This project started because I wanted a very compact and portable means for monitoring my 10m beacon. A direct conversion rceiver based on the popular NE602 / SA612 mixer ICs is just about the simplest design for a low parts count that works reasonably well. There are literally GOBS of DC designs out there based on the NE602 mixer. I followed some design choices from "W1FB's QRP Notebook" by Doug DeMaw, W1FB.
I assembled modules for each main part (filter, mixer, pre-amp, and audio amplifier) to allow for easy modifications and re-use. Instead of the most common 386 IC, I decided to go with push-pull audio amplifier using a 2N2222A and 2N2907A pair.
For a VFO, I used the DDS Signal Generator. The next step is package this all into a compact hand-held radio. I'm planning on using pluggable filters to allow for covering other frequency ranges as well.
Marten Beels 2015