This calculator will calculate the radiation resistance of a vertical antenna which is very short compared to the wavelength. This is typically the case for all antennas used by amateurs on LF (137 kHz) and MF (475 kHz). Formulas are taken from this excellent page by ON7YD.

Enter antenna height in metres:

Enter frequency in MHz:

Enter antenna impedance (dominated by ground loss plus inductor loss) in ohms:

Enter transmitter power output in watts:

The wavelength in metres is:

The radiation resistance in ohms is:

The antenna efficiency is:

The approximate antenna capacitance in pF is:

The required inductance in uH is:

The antenna current in A is:

The antenna voltage in V is:

The total radiated power in watts is:

The EIRP in watts is:

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