I am wondering what technology should I use to transmit data (enough for controlling the robot and receiving video) over dozens of kilometers and mountains ?
3 Answers
How far is it in kilometers? What radio frequency you can use? Do you need security (code the data)?
It strongly depends on your application, it seems you need a real-time connection (to control a robot).
In practice you can use an infrastructure such as telephony systems, GPRS or if you have enough resources you can use satellite solutions.
Another solution is to make a network or repeater of ZigBee modules.
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$\begingroup$ I was in fact thinking about transmission using en.wikipedia.org/wiki/Very_low_frequency since my original question, the project evolved, and now it might be a boat/robot on the sea, so there might be thousands of kilometers of distance, that's why using ionosphere reflexion seems to me a good idea, what do you think about that ? $\endgroup$ Apr 23, 2014 at 8:39
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$\begingroup$ @TrevörAnneDenise It would help if you edited this information on your robot into the original question so that people don;t have to wade through the comments. $\endgroup$– ThomasHApr 30, 2014 at 17:09
You can use high power(1W) radio modems such as digi XTend or RFD900 for controlling your robot. For video transmission you can use high power analog video modules. Using proper directional antennas such as patch antennas or helical antennas, you can easily go up to 20+ km in line of site.
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$\begingroup$ I was in fact thinking about transmission using en.wikipedia.org/wiki/Very_low_frequency since my original question, the project evolved, and now it might be a boat/robot on the sea, so there might be thousands of kilometers of distance, that's why using ionosphere reflexion seems to me a good idea, what do you think about that ? $\endgroup$ Apr 23, 2014 at 8:39
You're posting somewhat of a contradiction. If you want a radio signal with enough bandwidth to transmit video, then you'll have to use line-of-sight communications.
To do what you're asking, you'd need more of a network solution, or a very high vantage point (i.e. somewhere in the atmosphere) for your control antenna.
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$\begingroup$ I am now thinking about ionosphere transmission... $\endgroup$ Apr 23, 2014 at 15:05
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$\begingroup$ For what frequencies? VHF does not reflect off the ionosphere. $\endgroup$– IanApr 23, 2014 at 17:25