The 6 dB Rule
Because free-space path loss increases with the square of distance, doubling the distance means 6 dB of extra loss. The reverse also holds: adding 6 dB to the link budget doubles the theoretical range, losing 6 dB halves it. This rule lets you quickly estimate the distance value of every intervention in the field.
The rule provides a practical conversion that turns dB into concrete distance:
- +6 dB: range ×2. That means four times the transmitter power, or a total of 6 dB of antenna/placement improvement.
- +3 dB: range approximately ×1.41.
- −6 dB: range is halved. Five metres of thin coaxial cable, poor polarization match or a rising noise floor easily produce this loss.
- −10 dB: range drops to about one third.
Its field value shows up here: a 45 degree polarization mismatch costs 3 dB, and 5 metres of RG58 costs about 2.2 dB at 433 MHz. Together they are close to 5 dB and wipe out roughly 45% of the range. Losses that look negligible on their own must therefore be assessed together. The rule applies only to free space; in an obstructed environment loss grows faster with distance, so the real gain usually falls below this estimate.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety