First off, I am new to this, so feel free to shoot down my dreams and desires.  That being said, this is what I think I would like to try and accomplish

UAV with

- HAM repeater installed

- APRS transmitting

- Controllable camera

- In flight computer controllability <--- I hope that is a word....

- Decent flight time? Hour-ish?

My first thought/ choice for an airframe is a C-17(only because I cant find a C-5). The reasoning behind this is that it is large and fat.  Not that I am trying to create an overweight aircraft, but I want to stuff a bunch of crap in there.  

For control of the aircraft, I'm considering xbee.  Still not sure how it works, but I get the idea it plugs into a computer.  I was thinking Arduplane, however I am really unsure if you simply load a flightplan and it does its thing or if you can update what you want in real time.





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Where would you get the power to run all the radio gear?  I've got no idea how much power you're trying to run, but it sounds like it might be a pretty good drain on batteries.

I got some cheap serial radio modems for my application since there's a new crop of radios in the works that will deliver a lot better speed and range, so I figured I'd deal with short range until then.  Xbee is OK from what I've seen, but for my application I'll wait for a cheaper radio with 5X the range.

50mw @ 900mhz @ 156 kbps just isn't going to cut it.  1,000mw @ 415 mhz @ 500 kbps is just around the corner and is going to make those xbees look like an abacus next to a laptop.

To fly an hour+ with a lot of payload you're going to have to go with a gas engine.  There are some pretty decent little 4-strokes coming out of China for cheap.  But you're talking a pretty damn big plane then.

For the radio, I was thinking a self contained hand held and then mounting it in the a/c. The battery life is significantly longer than the drone would fly for.

The xbee website confuses me still. Some of those radios have a 40 mile range, but, how do you use them?

They just form a wireless USB cable if you will (simple version) that allows you to communicate with a laptop running a ground control station that allows you to reposition or trim your platform.

Do you currently fly anything?? That's the first step before committing expense gear to the sky.

Nothing as a UAV. I have a couple helis and a couple foam planes, but nothing fancy.

If you are good with a cross band repeater, you could just use an HT like a Yaesu VX-8R which also does APRS.  Although, I don't think it does APRS and the repeater function simultaneously.  If you want a single band repeater, I think the duplexer alone would be too much weight.

As a HAM (KO4JY) I never considered this but it would be perfect for SAR or other temporary operations.  I haven't flown my Bixler yet.  I'm still working on it but it has most of what you mentioned and I think it could carry the weight of a VX-8R.  I will check when I get if flying.  However the flight time might be an issue.  I haven't heard of anyone getting that kind of flight time out of a Bixler.  A big flying wing might be a good idea.  Something like the X8 has lots of room for batteries and should have plenty of lift.

I will let you know when my Bixler flies and how it does with the VX-8R.  Thanks for the idea.

I would suggest the Honda GX35 4-stroke motor driving a generator in parallel. you can use an electric motor with certain controllers to achieve the power generation. For an Airframe, you can probably get away with a Senior Telemaster or the like. We were getting 4 hours from a 12' wingspan eppler 210 airframe using the GX35, weighted to 30lbs.

Hope this helps!


On a GX35 you might be able to tap the magneto instead of using a generator.  But that would suck some power from your ignition which might not be the best thing.  Probably best to use a CDI ignition, ditch the flywheel, and run a small generator from the other side of the engine.

Using a UAV as a repeater is a great idea and it happens to works really well.  I have flown an Arcturus T-16 with a radio relay payload that was setup for the Forest Service VHF radios.  We were limited in our altitude during that flight campaign (1200' AGL) so we were only able to get a 10 mile radius on the range, but it was working like a champ within that range!  When radio comms are as important as they are to the firefighters in the field, it could be an invaluable asset to have a rapidly deployable radio relay that could extend the their radio range, especially in those situation where it is extremely limited by the surrounding terrain.  



Where did you hear about these 1000mw, 415 mhz radios? I'm interested.


I am also a Radio Ham (G0OOY) but haven't done much for the past few years. However I have been looking at doing this sort of thing. I have a hand held 2Mtr/70cms with repeater functions etc.

I have now bought an X8 Wing from and this is a fantastic plane. Enormous lift capacity; manufacturer says 2KG but it will lift more. Massive fuse, flight times of 1 hour easy if you choose the right motor battery combo. So easy to fly I am really impressed with it.

I haven't flown it with the hand held in yet but it will not be a problem carrying it. I need to check if 70 cms will interfere with the DX6i etc.

Made from EPO so easy to repair. See all 225 pages of this.

If you did order from BEV buy something for a dollar to make the price upto $200 for free shipping

Has any study been made of coupling a r/c gas engine to a small generator. The weight would be less than the 4-stoke motor, but so would the output. I see on eBay a 1 oz 6v generator operating at 12,900 rpm with a stall output of 2300 mA. Then a Google search for smallest generator turned up a Chinese wind generator weighing just over a half pound with a 6 v output, but no mention of amps. Diameter of the thing is 33mm (1.3 inches). I see you get about 1 hp per cubic inch with a weight under 2 lbs (less fuel). Looks like some sort of hybrid is possible for larger aircraft. I've no experience, but like the idea....


I'm working with parks in the Congo for anti-poaching and general surveillance of the parks (animal counts at watering holes, etc) and wondering about the "inverse" - if one might use digipeaters to maintain contact with at least the positioning, and perhaps send low-bandwidth commands (return to home, fly to a new waypoint, etc)

I'm very interested in lightweight APRS gear suitable for operation through digipeaters, and if folks have integrated them with autopilots...


Chris Nicholas

KK6LRS  (SF Bay Area)

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