"Egli" Calculator

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.

"Egli" Calculator

Attenuation = 117 + 40 x log(D) + 20 x log(F) - 20 x log (Ht x Hr)

Enter the values to calculate your propagation loss, or alternatively, enter an acceptable propagation loss, and the maximum transmission distance will be calculated.

 Variable factors to consider when using Egli Calculations:

• The distance between two sites
• The (possible) height of the antennas
• The transmit power of the data radio
• The receiver sensitivity of the data radio
• The antenna gain

Egli calculations are used to mathematically calculate propagation loss.  The value tells how much the signal strength is decreased due to the distance between the transmitter and the receiver. For this we use the Egli model. The Egli model is a simplified model that assumes "gently rolling terrain with average hill heights of approximately 50 feet (15 meters)" (Land Mobile Radio Systems, Edward N. Singer, PTR Prentice Hall, 1994, p. 196). Because of this assumption, no terrain elevation data between the transmitter and receiver facilities is needed. Instead, the free-space propagation loss is adjusted for the height of the transmitter and receiver antennas above ground.

As with many other propagation models, Egli is based on measured propagation paths and then reduced to mathematical model. In the case of Egli, the model consists of a single equation for the propagation loss.