If you’ve ever looked into ADS-B (Automatic Dependent Surveillance–Broadcast) systems for aircraft, you’ve likely come across the term 978 MHz UAT. This frequency band is critical to how modern aircraft transmit their location and other important data to air traffic control and nearby pilots.
In this article, we’ll break down what 978 MHz UAT is, how it works, how it compares to 1090 MHz systems, and whether it’s the right choice for your aircraft.
Table of Contents
✈️ What Is 978 MHz UAT?
978 MHz UAT (Universal Access Transceiver) is one of the two frequencies used in the ADS-B Out system, a core component of NextGen air traffic control in the United States.
- ADS-B allows aircraft to broadcast their position, altitude, velocity, and other information using GPS data.
- The “Out” part means the aircraft is transmitting (broadcasting) this data.
- The 978 MHz UAT frequency is specifically designated for general aviation aircraft flying below 18,000 feet (Class A airspace).
📡 How Does 978 MHz UAT Work?
The 978 MHz UAT broadcasts ADS-B Out information from the aircraft to ground stations and other aircraft. It also supports ADS-B In, allowing aircraft to receive traffic and weather data—something not available on 1090 MHz systems.
Key Functions:
- ADS-B Out: Broadcasts aircraft position and identity to ATC and other aircraft
- ADS-B In: Receives weather, traffic, and flight information services (FIS-B and TIS-B)
- Two-way communication on a single frequency
🔀 978 MHz UAT vs. 1090 MHz ES
| Feature | 978 MHz UAT | 1090 MHz Extended Squitter (ES) |
|---|---|---|
| Frequency | 978 MHz | 1090 MHz |
| Used For | General aviation below FL180 | Commercial and high-altitude aircraft |
| ADS-B In Support | Yes (weather and traffic) | No native weather or traffic broadcast |
| Broadcast Range | Medium | Longer range at higher altitudes |
| Ground Coverage | Good for low altitude | Nationwide at all altitudes |
| FAA Compliance | Yes, for aircraft below FL180 | Required for aircraft above FL180 |
🛩️ Who Should Use 978 MHz UAT?
978 MHz UAT is ideal for:
- General aviation aircraft flying below 18,000 ft
- Pilots who want free in-flight weather and traffic data
- VFR pilots needing affordable ADS-B Out compliance
- Aircraft that primarily fly in U.S. airspace (978 MHz UAT is only supported in the U.S.)
If you fly internationally or in Class A airspace, 1090 MHz ES is required.
🔧 Examples of 978 MHz UAT Equipment
Here are some popular 978 MHz UAT transceivers for general aviation:
1. uAvionix SkyBeacon / TailBeacon
- Easy install (replaces position light or tail light)
- ADS-B Out only (978 MHz)
- FAA compliant for 2020 mandate
- Budget-friendly and lightweight
2. Garmin GDL 88
- Dual-link (can receive both 978 MHz and 1090 MHz)
- ADS-B Out + In
- Integrates with Garmin avionics
- Great for IFR-capable aircraft under FL180
3. FreeFlight RANGR
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- Modular system with both Out and In capabilities
- ADS-B weather and traffic services
- TSO-certified
🌐 Limitations of 978 MHz UAT
- U.S.-only: The 978 MHz UAT frequency is not used internationally, limiting its usefulness outside the U.S.
- Not suitable above 18,000 feet: Aircraft flying at higher altitudes or in Class A airspace must use 1090 MHz ES.
- Receiver dependency: To benefit from ADS-B In (weather, traffic), you’ll need a compatible receiver and display.
✅ Advantages of 978 MHz UAT
- Lower cost than 1090 MHz systems
- Easier installation, especially with products like SkyBeacon
- Access to FIS-B (weather) and TIS-B (traffic)
- Ideal for GA aircraft flying domestically
📋 Final Thoughts
The 978 MHz UAT system offers an excellent, cost-effective solution for general aviation pilots who fly below 18,000 feet and within the United States. With access to free in-flight weather and traffic data, plus full FAA compliance for ADS-B Out, it’s a smart investment for most VFR and light IFR pilots.
However, if you fly internationally, at higher altitudes, or in Class A airspace, you’ll need a 1090 MHz ES transponder instead.
✈️ 978 MHz band ADS-B Receiver ⭐⭐⭐⭐⭐