15 Watt FM Transmitter Range Calculator

In this article we calculate the distance covered by a popular FM Transmitter.

FM transmitters are used in many different applications like outdoor drive in movie theaters. A typical FM transmitter has a maximum output between 0.1 Watt and 25 Watt. The one below transmits at 15 Watt.

Fail-Safe 15 W Long Range Professional FM Transmitter CZH-15A + Free 1/4 Wave GP Antenna
15 Watt FM Transmitter

FM Transmitter Range Calculator

In the calculator below, enter:

  • Transmitter power 15 Watt (converts to 42 dBm)
  • Receiver sensitivity (consistent with Rural, Urban or Large City)
  • Transmit Antenna Gain
  • Receive Antenna Gain

Example Calculation

According to the ITU, the following table shows required sensitivity in dBuV/m for FM in various environments. We have used the dBuV/m to V/m calculator to convert the units.

EnvironmentField Strength (dBuV/m)Field Strength (V/m)
Rural540.0005012
Urban660.0019953
Large Cities740.0050119

The field strength is used to calculate the input power at the receiver in dBm. In this case the antenna gain of 0 dBi is used. However you can substitute any value in this calculator.

The FM frequency range is 88-108 MHz.

EnvironmentField Strength (V/m)Power (dBm)
Rural0.0005012-64
Urban0.0019953-52
Large Cities0.0050119-44
FM required power

Note that cities are more challenging RF environments, so the required power for a certain level of performance is higher relative to a rural environment. There’s a 20 dB difference between the two. The receiver sensitivity values that can be substituted in the range calculator above.

What is the Range of a 15 Watt FM Transmitter?

Based on the calculation above, the range for different operating environments is:

  • Rural – 44 km or 27.5 miles
  • Urban – 11 km or 6.9 miles
  • Large City – 4.4 km or 2.75 miles

As would be expected the range is the lowest in a city where buildings and other large objects will obstruct the FM signal. This means it will not travel as far in a city as it will in a rural environment.