Radio Wavelength
Wavelength of a radio signal is the speed of light divided by its frequency; it sets antenna length and dish sizing.
Formula
Variables
Example
A 113 MHz VOR signal: λ = 3×10⁸ ÷ 113×10⁶ ≈ 2.65 m
How it works
Radio waves are electromagnetic waves, so their speed in free space is the speed of light. For any wave, speed equals frequency times wavelength, so rearranging gives wavelength = speed ÷ frequency. This is useful because a signal’s wavelength is directly tied to the size of antennas and other RF hardware that must resonate efficiently with it.
When to use it
Use this when you need to find the wavelength of an aviation radio signal, such as VHF comms, VOR, or ILS-related frequencies. It also helps when estimating antenna length or comparing how different frequencies behave in a system.
Worked example, step by step
Find the wavelength of a 121.5 MHz emergency frequency. λ = c / f λ = 3.0×10^8 m/s ÷ 121.5×10^6 Hz λ = 2.469... m λ ≈ 2.47 m
Common mistakes to avoid
- Using MHz directly instead of converting to Hz
- Mixing up wavelength and frequency by multiplying instead of dividing
- Rounding too early and losing accuracy in the final wavelength
Did You Know?
A quarter-wave VHF comms antenna at 120 MHz is only ~62 cm long — short enough to sit as a small blade on the fuselage.
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