Amateur Radio and AVR questions

[grenadapult]

I have two questions:

1-I am a licensed HAM operator. Does anyone know of a good way to interface into servo control, via HAM radio? There are special bandwidths allocated by the FCC for remote controlled crafts, but I have had a terrible time finding oout how to use them. i could feasibly get 15 miles or more of range that way.

2-Does anyone have info on an auto-pilot based on AVR microcotrollers instead of PIC? I messed around with AVR and have some at home, but am simply not familiar with PIC. I'd like to interface GPS, but just a gyro would be nice.

Thanks,
Tim

[Mrbmw99]

Tim,

I'm working on an AVR based autopilot. I've posted some info on the project on my website Piper Arrow II UAV (http://www.woollum.com/blog/). I'm planning on using multiple ATMega128's with Gyros, accelerometers, etc.

[grenadapult]

WOW!! Thats way out of my league, but still awesome. From a rational standpoint, I would think a mologogo cellphone would be the easiest way to GPS track the bird. The HAM operator in me says to use an ARPS system. ARPS (http://www.tapr.org/aprs.html)
I'm new to R/C airplanes in general, and have been building my own foamies that are full electric. For right now, I just wanted a simple flight stability system, but want to be able to add on later. I have a few varieties of Atmegas at home, including the Atmega 128. I had hoped to start with stability, add altitude, then add direction finding through compass and/or GPS.
Any suggestions for just the simpler stuff?.......for now :cool:

[Jack Crossfire]

HAM radio was my vision back in the 80's. Nowadays you can get 15 mile range using $40 XBee modems.

[kd7ost]

In Ham Radio, you can purchase radio's that have RF sections tuned to the 6 meter band. Some higher end RC Radio systems have plug in RF modules and you can get the modules that operate at 50 Mhz. There are 10 frequencies allocated to that all right around 50 Mhz. I have a Futaba computer radio like that. I can drop in the 72 Mhz or the 50 Mhz module and go fly with the appropriate receiver.

However, those RC Radio's have antenna's that are optimized for a fraction of a 72 Mhz wavelength. (Not sure if it's a 1/4 wave or not) When you drop in a 50 Mhz module, they simply have the tuning circuit on the RF output tuned to match the 72 Mhz fractional antenna. I find my Radio gets better range when I'm operating at 72 Mhz as apposed to when I plug in the 50 Mhz module.

However I realize your question is how to interface a different Radio to act as the Rf section. Tough stuff and a hurculean task. (I think) You have to have sticks and switches relating to all your channels going into an encoder chip and then have them go into your radio. The issue becomes huge and I don't know of anyone doing what your asking. Your radio transmitting 50 watts on (FCC authorized) RC channel 5 is at 50.9 Mhz. It isn't likely it will be narrow band and once you power up you can be shooting down any 50 Mhz RC pilot within a huge range. 15 miles is very conservative especially if you use a high gain antenna. But we don't even have to go there. The HAM radio regs limit you to one watt of output power. I don't recall if this is measured before the antenna or is EIRP.

I would be the first to suggest that you think through and task yourself with risk mitigation before even trying to fly at that range. It is considered pretty reckless by most save for a few rogue elements. A GPS return to pilot system in the event of failure is a must, but isn't even high on the list of risk mitigation features. See and Avoid of aircraft with people in them is something that can't currently be navigated around. A camera doesn't see well enough to replace the human eye and head on a swivel. Camera's, transmitters and power systems can fail leaving you blind. Ask yourself what is the worst case scenario, and then ask yourself if you can overcome any possibility of failure?

Dan
73's

Band plan chart
http://www.arrl.org/FandES/field/regulations/Hambands_color.pdf
RC Frequency Chart
http://www.blueangels.rchomepage.com/frequency_chart.htm