Fade Margin
Fade margin is the dB difference deliberately left between the calculated received signal level and the receiver sensitivity. Leaving 10–20 dB of margin is common engineering practice in field installations. This margin is there to absorb moving obstacles, multipath fading, rain, battery decline and fluctuations in the noise floor.
A link with zero margin works on paper but not in the field. The RF environment is not constant: a truck passes, the crane swings, the operator moves, and the received level can shift by 10–20 dB within seconds.
- The margin and its source are both in dB: 10 dB of margin means the link stays up even if the signal weakens tenfold.
- Distance equivalent: 6 dB of margin means working at half the theoretical range.
- Practical installation rule: if you need 100 metres, you want to use a set that gives 150 metres in open field in its comfortable region, not at its limit.
The range figures for AXI sets are for open field and line of sight. In an enclosed workshop, between containers or inside a steel structure you will drop noticeably below that figure; when selecting a system, the right approach is to choose one step up in comfort rather than the model that just barely covers the need.
Context where this term is used: Wireless remote control installation: pairing, relay, safety