Point-to-Point Links
From a radio perspective, point-to-point links are very straightforward to set up. You should always follow more or less the same steps when evaluating the possibility of a link:
Establish that you have line of sight from end to end.
Measure the distance between the points and calculate the path loss.
Add in the capabilities of your equipment to determine your link budget.
Go out and hook up your gear.
If you intend to make a long-distance point-to-point link, first find out the latitude, longitude, and altitude of each end point. You can find this by physically going to each site and marking the coordinates with a GPS, or you can estimate using topographical maps or software (see Chapter 6 for some examples of how to do this). With the coordinates and altitude of both sites, you can calculate a bearing and tilt angle, so you know roughly where to point the antennas on each end. A decent GPS can help here by giving you a bearing to and from each point. You should also check out the online wireless design CGIs at http://www.qsl.net/n9zia/wirelesspage09.html for help with many of the calculations you’ll need to perform.
Obviously, if you can see the other point through binoculars or a telescope, this is a good first step. Ideally, there should be very little on the ground between the two points. The closer the path is to an actual valley, the better. Take a look at Chapter 6 for details about how to calculate the path loss and link budget for your link. I’ve mentioned ...
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