Field strength meter

In telecommunications, field strength meter is a measuring device which measures the signal strength caused by a transmitter.

In ideal free space, the electric field strength produced by a transmitter with isotropic radiator is readily calculated.

where

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.

The factor ${\displaystyle {\sqrt {30}}}$ is an approximation of ${\displaystyle {\sqrt {\frac {Z_{0}}{4\pi }}}}$ where ${\displaystyle Z_{0}=119.9169832\pi \Omega }$ is the impedance of free space.

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