Replies to This Discussion

Permalink Reply by Reto on March 11, 2009 at 3:44pm

Out of sight RC flying is not allowed by law in most European countries and in the USA.
Though I understand the question is interesting on the theoretical level...
As to cellphones, the most interesting characteristic they have is that their successive positions, triangulated from the provider antennas, are stored for months by the providers in case a justice department needs them to document some unlawful activities.... like for example unauthorized long range UAV flights!
At least switch off the cell in your pocket when you launch your long range UAV...

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Permalink Reply by Ray on March 12, 2009 at 4:19am

wow i didnt know its illegal just to fly it, and i didnt belive you guys do all this work for just autopiloting ur rc´s at your backyards.. but you still have any good theories how its possible ?

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Permalink Reply by Noth666 on March 12, 2009 at 6:51am

Hi,

It's indeed illegal to do so privately without approvals and permits etc etc.
Most countries only allow unregulated flight privately if you stay under 300m and within line of sight.
But if you have the required approvals etc(only do it if you do!) there are several ways to do this depending on some parameters of how you need to fly.
First and simplest is long wave modem control directly, there are a few discussions for this on this forum also. This is limited in the way that you would most likely loose signal close to ground when far away and thus impractical for landing on a remote location.
This can be done up to ranges of hundreds of km but pre-testing and failsafes would be paramount - ie you should have programmed behavior to gain altitude and turn towards the transmitter if link lost - since with this setup loss of signal is usually not recoverable without action by the UAV, unlike the others below.

GSM/GPRS/HSDPA has certain advantages, such as high speed data, roaming, GPS integration etc, but are limited to actual coverage areas and bound also in some cases to operators and have other costraints. This is still fairly cheap.
The best thing with HSDPA is that the response time is comparatively fast (vs satellite) and you can use very small low power modules.

Satellite would be the way to go for global coverage. For low data amounts (no video etc ) I personally use Globalstar as it is cheap. The only downside is slightly unreliable link and no coverage over 200nautical miles out to sea.
The premium coverage way for low data amounts would be Iridium satellite data, very reliable, and truly global coverage including arctics etc. The downside of Iridium is cost/min and cost in general for sim cards etc.
BGAN could perhaps be used in a geolimited system but would require correct pointing so you would need to have GPS based tilt/pan on the dish and actively point towards the satellite, but this would give Mbit speeds, and could do live video from a remote vehicle. BGAN would also be the most expensive of the alternatives, but also the closest to what for example predators and global hawk use on long range missions.

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ModeratorPermalink Reply by Sgt Ric on March 12, 2009 at 10:01am

I use streaming video here at work and one disadvantage you failed to mention when using sat connections is their nasty habit of transmission of packets in clusters. (perhaps you alluded to it by saying "no video")

Real time sat video links suffer from choppiness not really related to speed or bandwidth, rather the packaging of data being sent to and from the satelite.

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Permalink Reply by daniel knight on December 21, 2009 at 6:35am

hi, where can i get a long wave modem, and why do u recommend that over a short wave modem?

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Permalink Reply by Ray on March 20, 2009 at 4:37am

im a toal newb so ill have a stupid question coz its hard to find this info> how does a basic UAV systeb setup looks like ? lets say i use the globalstar connection, i need to get a modem from them and connect it to the autopilot? also i found the EagleTree OSD Pro looks pretty cool, is that only a video overlay or is it an atuopilot itself ? my understanding is that u need an autopilot with some modem and gps?? and also what do i need for ground control?

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