I have been having fun messing around with an old DDS-60 board that I obtained some time ago. I have cabled it up to the Arduino. Here is the setup:
The DDS-60 is plugged into the Arduino breadboard. I have a small four line LCD display on a separate board below. The LCD is certainly not necessary for this project, but is nice to have.
Looking at the DDS-60 output on around 10 MHz, we see a nice clean signal.
A little more code and we have a simple QRSS beacon putting out about 1.4 V peak-to-peak signal into a 50 ohm load. Hooked up a simple Grundig G6 portable radio and cabled the audio out to the computer audio in. Using Spectran, we can see the 6 hertz FSK signal on 10.140 Mhz sending my call sign (KO7M).