If you’ve been flying in the United States since January 1, 2020, you’ve encountered the FAA’s ADS-B mandate—whether you realized it or not. But what exactly is ADS-B, and why has it become such a critical piece of modern aviation technology?
In this comprehensive guide, we’ll break down everything you need to know about Automatic Dependent Surveillance-Broadcast (ADS-B), from how it works to why you need an ADS-B In receiver in your cockpit.
Understanding ADS-B: The Basics
ADS-B stands for Automatic Dependent Surveillance-Broadcast. Let’s unpack that mouthful:
- Automatic: No pilot or external input required—it broadcasts continuously
- Dependent: Relies on aircraft systems (GPS, primarily) for position data
- Surveillance: Provides real-time aircraft tracking
- Broadcast: Transmits information openly for anyone equipped to receive it
Think of ADS-B as your aircraft constantly announcing, “Here I am, here’s where I’m going, and here’s how fast I’m moving.” It’s replaced traditional radar as the FAA’s primary surveillance method for air traffic control.
ADS-B Out vs. ADS-B In: What’s the Difference?
ADS-B Out: The Mandate
ADS-B Out is what the FAA requires. Since January 1, 2020, all aircraft flying in most controlled airspace must broadcast their position, altitude, velocity, and other data. This is what ATC uses to track you—no more depending solely on ground-based radar.
Required for:
- Class A, B, and C airspace
- Class E airspace at or above 10,000 feet MSL (excluding airspace at and below 2,500 feet AGL)
- Class E airspace over the Gulf of Mexico at and above 3,000 feet MSL
- Within 30 nautical miles of certain Class B airports (the “Mode C veil”)
- Above the ceiling and within the lateral boundaries of Class B or Class C airspace
ADS-B In: The Game-Changer
ADS-B In is optional, but it’s where the magic happens for pilots. An ADS-B In receiver allows you to:
- See traffic: View other ADS-B Out-equipped aircraft on your tablet or panel-mount display
- Get free weather: Receive Flight Information Service-Broadcast (FIS-B) weather data in real time
- Improve situational awareness: Know what’s around you without calling ATC
Here’s the key: you don’t need ADS-B Out to benefit from ADS-B In. A portable receiver like Stratux gives you traffic and weather even if you’re flying a vintage taildragger with no electrical system beyond a handheld radio.
1090ES vs. 978 UAT: The Two Frequencies
ADS-B operates on two frequencies in the United States:
1090 MHz Extended Squitter (1090ES)
- International standard used worldwide
- Required for aircraft flying above 18,000 feet (Class A airspace)
- Used by all commercial airliners and most turbine aircraft
- Traffic only—no weather broadcast on this frequency
978 MHz Universal Access Transceiver (978 UAT)
- U.S.-only frequency
- Available for aircraft operating exclusively below 18,000 feet
- Carries both traffic and FIS-B weather data
- Popular with general aviation pilots
Why dual-band matters: If you only receive 978 UAT, you’ll miss all the airliners and jets on 1090ES. If you only receive 1090ES, you’ll miss GA traffic on 978 UAT and you won’t get FIS-B weather. A dual-band receiver like the Stratux Dual Band receives both frequencies, giving you complete coverage.
FIS-B: Free Weather in Your Cockpit
One of ADS-B In’s best features is FIS-B (Flight Information Service-Broadcast). This service provides real-time weather data at no cost:
- METARs and TAFs
- NEXRAD radar imagery (regional and CONUS)
- PIREPs
- Winds and temperatures aloft
- NOTAMs and TFRs
- AIRMETs and SIGMETs
- Lightning data
FIS-B is broadcast on 978 UAT and updated every 5 minutes for most products. It’s not a substitute for a preflight weather briefing, but it’s invaluable for in-flight decision-making.
Why Every Pilot Should Consider an ADS-B In Receiver
Even if your aircraft is already ADS-B Out compliant, adding an ADS-B In receiver transforms your situational awareness:
- See and avoid: Traffic awareness is the best collision avoidance tool you can have. ADS-B In shows you traffic with precise position, altitude, and trend data.
- Weather awareness: Watching a line of storms develop in real time beats guessing based on a 2-hour-old briefing.
- Cost-effective: Portable receivers like Stratux cost a fraction of panel-mount systems and work with apps you already use (ForeFlight, FltPlan Go, iFly GPS, etc.).
- No subscription required: Unlike XM Weather or other satellite-based services, FIS-B is free. Forever.
Getting Started with ADS-B In: Stratux
If you’re ready to add ADS-B In to your cockpit, the Stratux receiver from Crew Dog Electronics is an affordable, proven solution. It’s an open-source receiver trusted by thousands of pilots, offering dual-band reception, WAAS GPS, and compatibility with all major EFB apps.
Best of all? It’s fully user-serviceable. Every component is replaceable, so you’re never grounded by a failed part. GPS module dies? Swap it yourself for $20. Compare that to sealed commercial units that require factory repair or replacement.
Check out the replacement parts section to see just how repairable your Stratux is.
Conclusion
ADS-B has fundamentally changed how we fly. ADS-B Out keeps you legal and visible to ATC. ADS-B In keeps you aware—of traffic, weather, and the airspace around you. Whether you fly a Cessna 150 on sunny Saturday mornings or a Cirrus on IFR cross-countries, an ADS-B In receiver is one of the smartest investments you can make.
The airspace is more crowded than ever. Make sure you can see what’s out there.