Relative directivity factor (RDF) is a figure of merit for
radio receiving antennas. It is the
antenna gain
In electromagnetics, an antenna's gain is a key performance parameter which combines the antenna's directivity and radiation efficiency. The term ''power gain'' has been deprecated by IEEE. In a transmitting antenna, the gain describes how ...
in the forward direction divided by the gain in all other directions. It is also called the
signal to noise improvement factor (SNIF).
References
Antennas (radio)
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