TPO↔ERP Calculator

Wireless regulators typically license broadcast stations by Effective Radiated Power (ERP). This is because broadcast licenses are more concerned with geographic coverage rather than transmission plant parameters, and ERP is a figure that aims to relate transmission plant parameters with the expected field strength as measured some specific distance from the transmitter.

To find ERP, you need the following information:

  • Gain of your antenna system in dBd
  • Total attenuation in dB of all sections of your transmission line at or near your assigned frequency
  • Total insertion loss in dB of any components in the RF signal path between your transmitter and the antenna
  • Transmitter power output (TPO) in watts

Convert your TPO to a logarithmic unit such as dBW or dBk, subtract the sum of every dB value for attenuation in the transmission line path, then add your antenna's gain in dBd. (If your antenna has negative gain in dBd, that will be equivalent to subtracting the absolute value of that number). The resulting figure is your ERP expressed in dBW or dBk.

With the same transmission plant parameters, you can also determine the TPO required to achieve a given ERP by inverting the operation. Convert the desired ERP to dBW or dBk first, then subtract antenna gain and add your transmission line path attenuation.

For more information, watch my video here:

Transmitter Power Output (Watts):
Transmitter Power Output (dBW):
Signal Path Attenuation (dB):
Antenna Gain (dBd):
Effective Radiated Power (dBW):
Effective Radiated Power (Watts):

This tool is provided as-is and without any warranty. You must ensure the accuracy of the parameters you enter. For regulatory filing, engage the services of a professional to double check your data.

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