Telemetry using audio channel of video transmitter

[m1tch37]

I saw this today:

http://vrhome.net/vassilis/2009/03/telemetry-using-audio-channel-of-video-transmitter/

I was wondering if anyone had any experience using a RC cam's audio channel as a modem?

I have never seen it done before in DIY UAVs. Can it be done? Is it effective?

[vassilis]

I was waiting until I had something more complete to talk about, but here is what I am planning to do.

I have a simple board (with a Parallax Propeller microcontroller and few other components) that I will use as an OSD and a downlink modem. As you can see on my blog the downlink modem works quite well, I have done ground tests and as long as there is video the link is reliable. When there is static the probability of dropping frames is increased.

The OSD is more or less done as well, I will be posting a video this weekend likely. What am I planning to do with this? Well, I just got my AttoPilot shipped today (thanks Dean!). The plan is to use my OSD/Modem board to display essential information (bearing, direction/distance to home, roll/pitch, battery etc) in the OSD and also downlink the data to the ground station through the audio link. For the ground station, I am not planning to use any additional hardware besides the a/v receiver.

With the above setup I am hoping that I will be able to use the AttoPilot to fly in FPV mode in addition to autonomous mode. Still some work to be done, once I have something working as a system I will be releasing the source code and design files.

Vassilis