Line of Sight Wireless Circuits

Posted on 05 Apr 2015 by Marek 
Google Maps map showing intended route of a line of sight wireless circuit.
Map from A to B, complete with half a dozen buildings obstructing the line of sight.

The challenge was to link two Alpine properties in a way to share the Internet access. The problem was a whole lot of buildings in the way.

We took some MikroTik SXTs to Wales to do some testing in a hilly area, driving around to see what the limit of the devices would be. One was mounted on the roof of a bungalow, while the other came with us as we explored. One of the great things about the MikroTik RouterBOARD range of devices is that they accept a wide range of voltages — which makes it easy to have one plugged into a cigarette lighter in a car!

Our adventure in Wales led to some surprising discoveries:

  • line of sight was not strictly necessary, and we were able to browse social media a good two miles away from our "base"
  • where line of sight is possible the SXT presents an incredible "war driving" opportunity, as hundreds of SSIDs in a nearby town were all scannable
  • the unlicensed 2.4GHz range is a very polluted piece of radio spectrum

We were reasonably confident that we would be able to achieve some success in the Alps… and so we packed our boxes and took them abroad.

Having arranged a very rough and ready test, proving a link did establish, we then needed to make the fixings a little more robust. At the "upstream" end we mounted the SXT on a custom-made wooden arm, stained to match the adjacent timberwork. The "downstream" end was a more temporary construction, allowing it to be removed and re-installed upon demand.

Using 2.4GHz was, as we expected, not perfect — occasional packet loss and high latency were less than ideal — but using 5GHz eliminated that problem. The customer has a rock solid link with capacity greater than their upstream Internet connection. A good result in spite of obstacles in the form of four houses and three blocks of flats!