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Cheap, long range, wireless data connection?

Discussion in 'Networks & Internet Connectivity' started by Messiah Khan, 16 Sep 2009.

  1. Messiah Khan

    Capodecina

    Joined: 1 Sep 2005

    Posts: 10,000

    Location: Scottish Highlands

    Here's a question;

    Is there anything out there that can provide a relatively cheap data connection (Ideally over about 20KBps) wirelessly, up to about 20kms or more in direct sight? One more rule to the game; It can't rely on networks etc that work on the ground, as I'm wanting it for something 20kms UP (as in towards space). :D

    so far I have found radio modems, an am doing a bit of reading, but wondered if there was anything else out there.
     
  2. howler

    Wise Guy

    Joined: 5 Oct 2004

    Posts: 1,647

    Cheap is going to be the killer for you there, you could look at laser
     
  3. bigredshark

    Man of Honour

    Joined: 30 Jun 2005

    Posts: 9,516

    Location: London Town!

    Laser is a good option, but the range is pushing it and they're sensitive environmental conditions (such as: rain, fog, mist, haze or anything which isn't 20:20 visibility).

    Microwave is the usual technology for this sort of thing but I think you'll struggle for cheap (and if you're talking 20km upwards, I'm assuming you aren't launching a full blown space mission so you're likely looking for something fairly compact and lightweight too)

    Most other technology uses licensed frequency, which obviously means a license, which is probably a killer on cost grounds already.

    Only two cheap-ish options I can see are laser (with it's limitations) or something GSM based might be possible (though I can't think of an exact setup right now). Microwave could be worth investigating but I suspect cost and bulk will be an issue...
     
  4. Azuse05

    Wise Guy

    Joined: 24 Apr 2009

    Posts: 1,950

    Location: Aberdeen, Scotland

    Forgive me, but why not directional antennas for a wifi link?
     
  5. bigredshark

    Man of Honour

    Joined: 30 Jun 2005

    Posts: 9,516

    Location: London Town!

    To get that kind of range you'd need to exceed the legally allowed power output I'm fairly sure (or have a very sensitive reciever and very little background noise).

    For reference GSM signals basically have a maximum (theoretical range of 22 miles (around 100,000 feet), which makes even that marginal. So you're getting pretty specialised. Good news is you don't want heaps of bandwidth at least - other question is do you need two way comms?
     
  6. quickshot89

    Wise Guy

    Joined: 1 Feb 2009

    Posts: 2,041

    with a decent pair of attena and a clear line of site 20km should be possible, but your looking at +20db gains here, and thats quite expensive

    edit: forgot about power output laws (damn! )
     
  7. Messiah Khan

    Capodecina

    Joined: 1 Sep 2005

    Posts: 10,000

    Location: Scottish Highlands

    Thanks for the suggestions. I think I can rule laser out due to how accurate it would have to be aimed, and problems with clouds etc.

    1 way comms would be fine tbh, although 2 way would be a bonus. Basically I'm thinking of launching a high altitude weather balloon, but would like to to transmit image data down as it goes up. A target of 100,000 feet would be great, so as you say GSM is marginal, but still an option.

    One option that looks possible is something like;

    http://www.digi.com/products/wireless/point-multipoint/xbee-pro-868.jsp
     
  8. J.B

    Soldato

    Joined: 16 Aug 2006

    Posts: 5,922

    I've used digi stuff before on a project, its pretty good if your good with the old electronics and code you will get it working no problem.

    Personally I think it's probably the best option.

    Are there different rules on what can be used (RF wise) at altitude?
     
  9. bigredshark

    Man of Honour

    Joined: 30 Jun 2005

    Posts: 9,516

    Location: London Town!

    Looks like a good option if you have the experience to integrate that module into a communications system.

    GSM is maybe an option as you say, if you send it straight up above a base station, any lateral movement and it'll drop pretty quickly I'd expect though.

    Interesting project anyway!