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What is Radio Line of Sight?


Microwave radio signals require a clear path between your antenna and our access antenna. Using binoculars on a clear day, it is relatively easy to determine if visual line-of-sight exists between two points that may be many miles apart. If you cannot achieve visual line-of-sight it is unlikely that you can achieve radio line-of-sight. The most common cause is too many large trees in the path. Even if you can get visual line-of-sight that doesn't mean you can achieve radio line-of-sight. Radio signals do not travel in a tiny beam like light does, radio signals spread out into an area knows as the Fresnel (pronounced fra-nell) zone. If there is visual line-of-sight, but an object is blocking the lower half of the Fresnel zone, there will be a reduction of about 50% of the signal which may mean that there is not enough signal to make it work.

We will show this with a few simple diagrams where the access antenna is on the top of the grain elevator leg on the silos at the right, and your house is on the left with the obstruction, also known as a tree, in the middle. The dark blue line represents the visual line-of-sight, and the shaded area represents the fresnel zone of the radio line-of-sight.

An example of visual line-of-sight: (You can just see the access point from the chimney of the home.)
Diagram

In short, the fact that you are in range on our map does not mean that you can get the service. Sometimes you may even be able to see our access point and still not be able to get the service.

An example showing a visual line-of-sight, but reduced radio line-of-sight: (if you are close, this will still work)
Diagram

There are some options to be able to get the service.

You can raise the antenna mounting location high enough to clear the obstruction.

Put up a tower tall enough to clear the obstruction.

Locate a different mounting location for the antenna that may have radio line-of-sight.

An example showing a radio line-of-sight by using a TV tower:
Diagram

The difficult part with the tower is to determine exactly how tall it has to be to achieve full radio line-of-sight.

Or as a last resort, remove the obstruction. In other words cut down the problem tree(s). Of course this one gets to be a bit of a problem if the obstruction is your neighbour's house, and not a tree.

An example showing to removal of the obstruction:
Diagram

If you decide you must follow this path, we ask that you be environmentally responsible and plant 10 new trees to take the place of the mature tree you cut down.

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