You can have a look at my blog for a longer explanation, but the short-ish version:

It is currently only a receiver, no transmitter stages so far.

This project originally started off as a simple transceiver, meant to run from a 5V source, like a cheap USB battery. The reason here is so many cheap USB battery packs and also being able to reuse a USB pack for Amateur Radio. I soon found out I could not easily run a transmit power amplifier from 5V, but this may still happen later, with some sort of up-converter, probably to 24V. The receiver section completely runs off 5V.

I then started to change direction a little, thinking about the TenTec 507 Patriot, an Arduino based open-source transceiver, and thought that I could do something like that in this project, like adding a DDS. I want to take this further and have the microprocessor control all functions of the radio.

The DDS is just a cheap AD9850 module from eBay and it drives the circuit well. I moved to a Arduino Nano clone briefly, but had trouble driving the LCD, I later found that the SPI driver for the AD9850 uses pins 10 & 12, even if they aren't actually used, and I will move back to the Nano for size.

The display is not permanent, it's just there for debugging. Firstly, there just aren't enough IO pins to do everything, at a later date a display might be added via serial IO. Secondly I want this to be dead simple with less things to drain power, I am thinking along the lines of the TenTec Rebel, Patriot and the LNR Precision Mountain Topper.