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This page contains some useful formulas for radio "link budget" calculations. Note that the calculations are based on assumptions of certain circumstances and should only be used as a guideline for radio network design. In reality, many factors can have an impact on the radio link. Planning of a radio network is usually done by first simulating the network in a desktop propagation study using a professional software package. The results are then verified by performing a field survey.

However, the calculators on this page can show whether the radio link has an acceptable fade margin or, if not, how much antenna gain needs to be added, or if repeaters have to be used.

This Egli calculation is used for propagation loss. This value tells how much the signal strength is decreased due to the distance between the transmitter and the receiver. 

The free space calculator shows the theoretical attenuation with no terrain considerations. Again, you can enter a value for Distance and see the Attenuation, or alternatively enter a value for Attenuation, to see the maximum Distance.

This page converts between two common units for radio power - Watts (W) and Decibel "milliwatts" (dBm).

This is a calculation for those who are unable to view the Egli and Free Space Calculations, or would prefer to see an example of the formula used in working practice.

This is a calculation with all the possible losses in the system and subtracting the losses from the line of sight to give an estimated value of your likely link performance.

This is a calculation which gives the likely link performance where there is no interference between a clear line of sight transmission.

Radio Fade Margin is an expression for how much margin, measured in dB, there is between the received signal strength level and the receiver sensitivity of the data radio.