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Wireless & Mobility · Intermediate

Six Decibel Rule

Each doubling of distance causes approximately 6 dB of additional free space path loss.

Definition

The 6 dB rule is derived from the inverse square law and lets engineers estimate range changes quickly. Conversely, a 6 dB increase in link budget roughly doubles the achievable distance in free space. It is commonly used in outdoor bridge planning.

Example

If a link works at 1 km with 6 dB of margin left over, it could theoretically reach 2 km.

Exam tip

Do not confuse with the 3 dB rule, which is about power doubling, not distance.

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