Rain Fade or Interference? How to Tell What's Really Killing Your Link
Learn how to distinguish between rain fade and RF interference in satellite communications, correlate spectrum data with weather patterns, and apply the right mitigation strategy for each scenario.
This article is part of our Satellite Spectrum Interference & Congestion: Operator Field Guide
Rain fade is atmospheric attenuation from rain, snow, and storms—especially above 11 GHz—that shows up as a broad, weather-correlated drop in signal level across affected paths. RF interference is man-made energy from other transmitters (satellites, 5G, radar), which typically appears as extra carriers or elevated noise in specific bands and does not track local weather. NOCs need a fast way to decide which one they are dealing with, because the mitigations are completely different: UPC, site diversity, and ACM for fade versus interference hunting, filtering, and coordination for man-made sources.
Four Diagnostic Dimensions
Does the degradation track weather? Rain fade correlates with precipitation intensity along the satellite-to-antenna path and often affects multiple links sharing the same region. Interference usually does not line up with rainfall and may appear or disappear due to human activity regardless of weather.
What does the spectrum look like? Rain fade shows a broad drop in signal level without new carriers visible. Interference shows unexpected carriers, elevated noise in specific frequencies, or structured emissions from terrestrial systems.
Which frequencies are affected? Rain fade hits Ku and especially Ka hardest, with C-band mostly resilient. Interference can hit any band where unwanted emitters operate.
How does the link recover? Rain fade recovery follows the storm profile—gradual improvement as precipitation lightens. Interference may resolve suddenly when a transmitter is switched off, or persist indefinitely if the source is permanent.
Quick Diagnostic Runbook
Step 1: Check weather alignment—is there heavy rain or snow along the satellite-ground path? Step 2: Inspect spectrum—are carriers simply weaker, or is there a new carrier or elevated noise? Step 3: Review link behavior—did ACM downgrade modulation gradually (fade) or did performance collapse suddenly (interference)? Step 4: Cross-check bands—are lower-frequency links stable while higher-frequency ones degrade (fade signature)? Are only specific carriers hit (interference signature)? Step 5: Escalate appropriately—if rain fade, apply UPC/ACM/site-diversity playbook; if interference, engage interference-hunting and geolocation workflows.
Why Getting This Right Matters
Rain fade can make links more sensitive to interference by eating into fade margin. A link that survives mild interference in clear weather can fail when the same interference combines with a rain event. Customers may blame weather when the real issue is interference, and NOCs can make the same mistake without correlating spectrum data with both weather and the RF environment. Getting the classification right is critical for SLAs, regulatory reporting, and commercial decisions.