The signal-to-noise and distortion ratio (SINAD) is a measure of the quality of a signal from a communications device, often defined as where
Note that with this definition, unlike SNR, a SINAD reading can never be less than 1 (i.e. it is always positive when quoted in dB).
[5] A typical example, quoted from a commercial hand held VHF or UHF radio, might be: This is stating that the receiver will produce intelligible speech with a signal at its input as low as 0.25 μV.
Radio receiver designers will test the product in a laboratory using a procedure, which is typically as follows: According to the radio designer, intelligible speech can be detected 12 dB above the receiver's noise floor (noise and distortion).
This article incorporates public domain material from Federal Standard 1037C.