What are Spurs?
Spurs are frequency responses higher in frequency than the main response but not as high in frequency as the next regular overtone. The word “spur” is used as an abbreviation of the word “spurious” but the frequencies described by either of the two are not “spurious” at all. They are regularly occurring natural frequency responses, the amplitude of which is subject to some degree of control through crystal unit design. Please see the Tech Note on Spurious Responses for a more complete explanation. 16.