What is signal attenuation?
Signal attenuation is the loss of signal strength as an electromagnetic wave travels from a transmitter to a receiver. Even in a perfect vacuum with no obstacles, signal power spreads out over an expanding sphere and weakens with distance.
The formula
This calculator uses the Friis free-space path loss formula in its common practical form: FSPL (dB) = 20log10(dkm) + 20log10(fMHz) + 32.44, where d is distance in kilometers and f is frequency in megahertz. This shows attenuation doubles (in dB terms, adds about 6 dB) each time distance or frequency doubles.
This formula models free-space conditions only; real-world links also lose signal to atmospheric absorption, obstacles, reflections, and multipath fading, so actual attenuation is typically higher. This calculator is for general RF engineering education.