How long can a link between two LibreRouters be?

This is a question that comes quite often, and it has three main factors that affect it:

  • the distance between the two points want to be connected
  • the line of sight
  • the country you are in

These three issues are affected by these two calculations that will be explained below:

  • fresnel zone clearance
  • power budget

The distance between the two points want to be connected

The distance you need to know because you will need it below.

Line of sight

Any wireless link with the LibreRouter radios will require line of sight, that it basically means that there must not be any obstacle in between the two points that are being connected.
It will additionally require something called fresnel zone clearance, what in layman terms means that there is space above and below the line of sight. You can imagine the fresnel zone as the shape of a hanging rope from one place to the other… the longer the link, the taller the rope will hang.
The math is related to the distance and the frequency. You can use this site, and the frequency is 5.8Ghz:

The country you are in

The reason why this is important is because the LibreRouter uses this information to configure itself to respect your countries maximum power regulations, and this affects the power budget.
The power budget is an equation that is used to know if a link is theoretically feasible or not.
It relies on the power output of the radio of the router (how much energy it comes out of it), the gain of the antenna, the distance in between the radios, and the frequency it is transmitting in two figure out if it is feasible or not.
We will do some maths for you to have this information at hand.

Common scenarios

To be completed with a table with some distances and speeds with stock antennas.

What to do if the link is not feasable

There are plenty of things to do:

  • add another LibreRouter in between
  • change the antennas
  • ensure you are using the right country configuration
  • get a license to use more power