• An instrument which is utilized to measure the wavelength of a signal, especially that of a radio wave. Such an instrument may consist, for instance, of a tuned circuit incorporating a variable capacitor, and a resonance indicator. Examples include absorption, cavity, coaxial, and heterodyne wavemeters. A wavemeter can usually be utilized as a frequency meter, and vice versa, as either quantity can be obtained knowing the other, according to the following formula: Λ = c/f, where Λ is wavelength, c is the speed of light in a vacuum, and f is the frequency.