The EZAD9850 Library will get you up and running on the Arduino with inexpensive AD9850 based frequency generator modules.

This Arduino library makes easily available control of an AD9850 module’s frequency and phase as well as starting and stopping frequency generation. Useful for a variety of radio projects and as a sine-wave generator. Operates from 0 – 40 MHz.

For sine wave output the outputs seem to have around 0.5V amplitude and around 100 ohms output impedance.

ad9850-arduino
A simple library for arduino to control an ad9850 DDS synthesizer
https://code.google.com/p/ad9850-arduino/

DDS-AD9850 + Open oscilloscope – Lxardoscope
http://www.elecfreaks.com/2110.html

Here we will show you how to control AD9850 module by Arduino, and then show the output wave by Lxardoscope, which is an Arduino based oscilloscope for Linux, using the Xforms library.

AD9850 useful test sketch for Arduino(-s)
https://gist.github.com/raivisr/3861473

Serial comms – 9600, NewLine (0x0A) denotes end of input,
f 10000 – set frequency
s 20 20000 10 1000 – sweep from frequency to frequency using this step size in that many milliseconds
o 10 10000 5 3000 – oscillating sweep from frequency to frequency and back using this step size in that many ms

0-40Mhz, Sine wave generator for $25
http://www.instructables.com/id/0-40Mhz-Sine-wave-generator-for-25/

With only 4 control wires we can control the board via the arduino. This gives us a variable sine wave generator that we can control to give us a very nice sine wave from 0 Megahertz up to around 40 Megahertz at almost a full volt peak to peak.

I decided to use a $7 LCD keypad to give some on screen visual indication of the frequency plus a means of controlling the frequency quickly and easily.

The code to upload to the Arduino, can be relatively straight forward.

0-40Mhz, Sine wave generator $25.
http://tobyrobb.com/wordpress/?p=577

I decided to use an LCD keypad to give some on screen visual indication of the frequency plus a means of controlling the frequency quickly and easily.

[m0xpd] is back again, this time using the AD9850 DDS module as a radio beacon with an Arduino.

Arduino Beacon
http://m0xpd.blogspot.co.uk/2013/02/arduino-beacon.html

I represented the DDS module as a component in Eagle

The module only took up a small fraction of the available area on the shield, so I added a couple of dual flip-flops to generate a quadrature squarewave output for future games

Bode plots on an oscilloscope
http://hackaday.com/2013/08/19/bode-plots-on-an-oscilloscope/

The basic idea behind [Dave Jones]’ impromptu Bode plotter is to configure a frequency generator to output a sine wave that ramps up over a period of time. Feed this sine wave through a filter, and you have amplitude on the vertical axis of your ‘scope and frequency on the horizontal axis. Boom, there’s your Bode plot.

[Andrew] did [Dave] one better by creating a small circuit with an Arduino and an AD9850 sine wave generator. Properly programmed, the AD9850 can ramp up the frequency of a sine wave with the Arduino outputting sync pulses every decade or octave of frequency, depending if you want a linear or log Bode plot.

Bode Plot on an Oscillscope
http://reibot.org/2013/08/16/bode/