Makers – Test Equipment Builds
The ability to generate a signal at a known frequency an essential tool for your shack. Dean, KK4DAS demonstrates this simple-to-build Arduino-based signal generator that can be used as a reference signal or even a local oscillator for a receiver. Watch the presentation on YouTube: (1) Using Arduino components to build a signal generator – YouTube

and get all the details building it yourself on the KK4DAS blog:

KK4DAS – Amateur Radio Explorations: Homebrew Signal Generator – Arduino and AD-9850 Module