Wavelength is the physical spacing between adjacent peaks or nulls in the electromagnetic field of a radio wave. Represented by the lower case Greek lambda (µ), it's inversely proportional to operating frequency (f). The generic formula for calculating wavelength is:
µ = 300/fMHz where wavelength is in meters
µ = 984/fMHz where wavelength is in feet
At microwave and high-UHF frequencies, the dimensions are very small, and smaller units are more appropriate:
µ = 300,000/fMHz where wavelength is in millimeters (mm)
µ = 11,808/fMHz where wavelength is in inches
The most common antenna lengths are fractions of a wavelength, specifically µ/2 and µ/4. When building the antenna with wire, tubing, pc-board copper, or any other conductor, the actual physical length varies, depending on various factors like closeness of adjacent objects, dielectric constant of any base, and conductor thickness. In all cases, the actual physical length is shorter than the computed value, and the optimum length is almost always determined experimentally.