In ideal free space, the electric field strength produced by a transmitter with an isotropic radiator is readily calculated.
It is clear that electric field strength is inversely proportional to the distance between the transmitter and the receiver.
However, this relation is impractical for calculating the field strength produced by terrestrial transmitters, where reflections and attenuation caused by objects around the transmitter or receiver may affect the electrical field strength considerably.
Most modern FS meters have AF and VF circuits and can be used as standard receivers.
Some FS meters are also equipped with printers to record received field strength.
A value of standard height frequently employed for VHF and UHF measurements is 10 metres (33 ft).