In this article we calculate the distance covered by a popular FM Transmitter.
FM transmitters are used in many different applications. A typical FM transmitter has a maximum output between 0.1 Watt and 25 Watt. The one below transmits at 15 Watt.
FM Transmitter Range Calculator
In the calculator below, enter:
- Transmitter Power 15 Watt (converts to 42 dBm)
- Receiver Sensitivity (refer to the second table below for 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.
| Environment | Field Strength (dBuV/m) | Field Strength (V/m) |
| Rural | 54 | 0.0005012 |
| Urban | 66 | 0.0019953 |
| Large Cities | 74 | 0.0050119 |
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.
| Environment | Field Strength (V/m) | Power (dBm) |
| Rural | 0.0005012 | -64 |
| Urban | 0.0019953 | -52 |
| Large Cities | 0.0050119 | -44 |
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.
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