I just got a Quanum Nova, which is a fantastic APM-powered copter that in many way outperforms the DJI Phantom for less than $300. Although it's capable of full autonomy, just like any other ArduCopter, the one thing it's missing for easy field mission planning and DroidPlanner compatibility is telemetry.
In this great tutorial, Jean-Louis Naudin shows how to add that:
Here an explanation for connecting the real time telemetry to the CX-20 or to the Quanum Nova
The telemetry port is located on the I/O board of the APM (the second board at the bottom and pluged to the main CPU board) where all the I/O plug are connected. The telemetry port is fully compatible with all the telemetry transmitter (3DR and all the compatible boards) and also with the Bluetooth boards commonly used with the APM boards.
Below the pinout which shows the telemetry port I/O (back to the I/O board).
Note from the comments: depending on which radio you're using, you may have to reverse the TX and RX lines. Dmitry in the comments reports: "You must connect RX from the radio to TX on the APM! And vice versa for Radio TX. So I've changed green and yellow wires and it works!"
sold 4 cables on the telemetry ports then protect the connections with hot glue
Check the functioning
The 4 pins telemetry plug is installed on the back of the fuselage
Check the connection (at 57600 baud) with the mission planner or the Droid Planner 2
Then, you may enjoy to use the telemetry...