FM Transmitter Range Calculator

An FM transmitter broadcasts a signal in the frequency range 88-108 MHz. The transmitting antenna emits the electromagnetic waves that carry the signal.

The coverage of an FM transmitter and its antenna system is determined by the power of the signal and the sensitivity of the receiver.

In general, an FM transmitter with a higher power output will have a greater coverage than one with a lower power output. Another important factor is the operating environment. FM signals will travel further in rural areas than in a city.

To calculate how far the FM signal will travel enter the Transmit power in either dBm or Watt. As well, select the propagation environment.

Formula

An antenna range calculator can be used to determine the path loss between two antennas. The path loss is the amount of power that is lost as a signal travels from the transmitter to the receiver. The calculator takes into account transmitter and receiver antenna gains and the distance between them. It uses the free space path loss equation:

FSPL = 20*Log10(d) + 20*Log10(f) + Lc + 20*Log10(4π/c) – GTx – GRx

FSPL calculator assumes ideal conditions of free space.

This Range calculator by comparison uses an Attenuation factor that’s consistent with the environment [1].

Example Calculation

An FM transmitter with an output power level of 1 Watt or 30 dBm has a range of 11 kilometers or 7 miles in a rural setting.

The same power level is able to reach 1.1 kilometer or 0.7 miles in a large city. in other words, the range is only 10% in a congested environment on account of large buildings and other obstructions.

The table below summarizes distance covered by a 1 Watt FM transmitter

Summary

The FM range calculator provides an estimate of the distance that an FM signal can travel. It is useful for RF planning purposes. For instance you can use it to calculate whether you will be able to receive an FM signal that is a known distance away.

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