I looked at buying an ArduCopter today, and was confused by why there are two options for communicating with the vehicle: RC, and "Telemetry".
After a bit of research, it seems that "RC" is radio communication, one-way, from the ground to the vehicle. "Telemetry" is radio communication, both ways.
If that's true, then what is the point of RC? Especially since the Telemetry option costs $85 and the RC option is $300. Why not just control the plane with the telemetry interface? I understand that some people like to use a joystick, so you could just plug a USB joystick into any device, stick the telemetry interface in another USB port, and that should be fine. Right?
Replies
Here's the thing abour RC and Telemetry from a radio guy perspective: RC has one purpose, sending radio signals from a transmitter to a receiver to control motors and servos. These signals require little bandwidth, have very low latency and packet loss. Serial telemetry uses radio modems for data transmissions. A higher bandwidth is required to transmit more data (i.e. telemetry) across a single frequency. The term MODEM is an acronym that means Modulate/Demodulate. The transceivers (transmit and receive from same source) are required to send larger packets of data which means higher packet loss and longer latency times. You will find that more issues arise with radio modems than RC because of the simplicity of modern day RC systems versus the complexity of wireless serial transmission.
I hope this helps clear up the mud a little!
You need RC for the initial setup and for backup if the telemetry drops out. Once it's set up and tuned you can fly with just telemetry.
There are cheaper RC options that will work fine, such as this one.