Fade Margin
Calculate the fade margin, M = P_rx − S, subtracting the receiver sensitivity S (dBm) from the received power P_rx (dBm). The result, in dB, is the slack between the arriving signal and the minimum the receiver can demodulate — the reserve available to absorb temporary fades caused by rain, multipath, vegetation and atmospheric variations. Reliable links typically require margins of 10 to 30 dB, depending on the desired availability and environment. It is the final check of a radio link budget. Enter the received power and the receiver sensitivity.
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Fade margin
A link budget may show that the signal arrives strong enough on average — but radio propagation is never constant. Rain, fog, multipath (the signal arriving over several reflected paths that alternately reinforce and cancel each other), swaying vegetation and atmospheric variations make the received level fluctuate over time. The fade margin is the reserve designed in to survive those dips: M = P_rx − S, the difference between the received power P_rx (dBm) and the receiver sensitivity S (dBm, the lowest level it can still demodulate at an acceptable error rate). The result, in dB, is how far the signal can drop before the link stops working. A margin of 0 dB means a link right at the edge — any fade takes it down. In practice, reliable links are designed with margins of 10 to 30 dB, chosen according to the target availability (99.9%? 99.99%?), the distance, the frequency and the regional climate (heavy rain calls for larger margins, especially above 10 GHz). The fade margin is thus the final check of a link budget: once EIRP, losses and gains have been tallied, it confirms that enough headroom is left. Enter the received power and the receiver sensitivity.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.