ADS-B – What Should You Know

The Basics                  Return to

Automatic Dependent Surveillance-Broadcast (ADS-B) is an acronym for:

  • Automatic
  • Dependent
  • Surveillance
  • Broadcast

Through ADS-B, ATC will, in the near future, track aircraft. It’s part of the Next Generation Air Transportation System (NextGen), which will replace our aging radar system with a satellite-based system. NextGen is more concerned with the increasingly congested flight levels and delays at major hubs, but GA must still participate. GPS and NextGen technology will be used to shorten routes, save time and fuel, reduce traffic delays, increase capacity, and permit controllers to monitor and manage aircraft with greater safety margins. Planes will be able to fly closer together, take more direct routes and avoid delays caused by airport “stacking” as planes wait for an open runway.

NextGen will be implemented across the United States in stages between 2012 and 2025. With that in mind, the United States will require the majority of aircraft operating within its airspace to be equipped with some form of ADS-B “Out” capability by January 1, 2020. The rule does not mandate ADS-B “In” capability. I’ll discuss more about ADS-B – “Out” and “In” later.

What? No RADARs? ADS-B will not be replacing radars anytime soon. The FAA plans to keep all long-range radars, but decommission many of the terminal short range radars at smaller airports after the 2020 ADS-B mandate goes into effect. We’ll still need radar:

  • As a backup in case of GPS failure, and
  • For national security.

The ADS-B rule, like current transponder operating requirements, requires operators to have, at a minimum, ADS-B Out avionics installed and operating in order to fly their aircraft almost everywhere but in Class G airspace.

What is the difference between ADS-B In and Out?

ADS-B “Out” systems are “Report Only”. They automatically broadcast an aircraft’s GPS position to ATC about every second. The 2020 mandate is for ADS-B “Out”.

ADS-B “In” systems not only broadcast/report an aircraft’s GPS position, but they also receive broadcasts from:

  • Other aircraft, and
  • FAA ground stations. These FAA broadcasts include:
    • Traffic information from other aircraft – Traffic Information Services – Broadcast (TIS-B)
    • Weather and NOTAM information. Flight Information Services – Broadcast (FIS-B)

The data received with an ADS-B “In” system is dependent on the ADS-B link and the capabilities of the receiver.

Equipment Required

To participate in ADS-B, you’ll need a GPS, so ATC can read your position, vector, altitude and speed. Portable GPS units don’t qualify. The GPS must be panel mounted, and the USA has mandated that the GPS have WAAS-like capability, such as the Garmin GNS 430W (shown here) or the GNS 530W. There are also newer Garmin market entries like the GTN 650, costing about $11,500 + installation, and the larger GTN 750, starting at about $17,000 + installation. Both are WAAS capable.

ADS-B option 1: Install a 1090 MHz “extended squitter” (ES) transponder. “Squitter” is not a word I would have imagined to have entered my aviation vocabulary. Yet there it is, with all the distasteful images. The Garmin GTX 330 transponder with Mode S fits the bill. It’s designed for ADS-B. The GTX 330 costs about $3,500 + installation.

The 1090ES is ADS-B “Out and somewhat In” capable. That is, it will receive traffic information (TIS-B)– but it will not receive weather information ( FIS-B).

The 1090 MHz ES link data allows you to broadcast the data from the GPS source to both ground stations and other aircraft in your vicinity.

If your aircraft flies outside the USA or flies at or above FL 180 (18,000 feet MSL), the FAA will require you to use the 1090 MHz ES link (Mode S transponder).

Aircraft and pilots that fly below FL 180 or remain in the USA, can use either option 1 (the 1090 MHz ES) or they can –

Choose option 2 – UAT: Install a dedicated 978 MHz Universal Access Transceiver (UAT). With a compatible UAT, you will be able to participate in ADS-B In. That’s because the transceiver will also receive data linked weather (FIS-B) and traffic display (TIS-B) – displaying the data on your GPS’ screen. The Mode S just doesn’t have the bandwidth for FIS-B  – too busy squitting about, I suppose.

If you choose the UAT option, NavWorx produces the ADS600-B, a remote mounted UAT that transmits ADS-B OUT information, and receives ADS-B IN information. This will cost about $2,500 + installation.

ADS-B Coverage as of Feb 27, 2012

NOT A 2020 ADS-B REPLACEMENT: A new product, aiming to take advantage of the ADS-B data linked weather (FIS-B) is the Stratus. It’s a lightweight, low-profile, battery powered (up to eight hours on a charge), ADS-B/GPS receiver that connects to the iPad completely wirelessly and provides extremely accurate GPS position in addition to ADS-B weather. It’s essentially a Wi-Fi hotspot for your iPad and ForeFlight. The Status costs about $800, with NO monthly fees. Flying Magazine reviews the Stratus at

NOT A 2020 ADS-B REPLACEMENT: A newcomer to the Wi-Fi/ADS-B weather market is the Sagetech Clarity ADS-B Receiver. It’s not on the market yet, but seeks to offer an alternative to the Stratus. Its features are discussed at

Projected ADS-B Coverage by the end of 2013

Puerto Rico, Guam and Hawaii will be fully covered in 2013.

Note the lack of coverage below FL180 in parts of Nevada, Arizona, New Mexico, Colorado, Idaho, Kansas, Wyoming, Montana, South Dakota, and Oregon.

The Bottom Line

For the Class B, C and E phobic, you’re in luck, there’s always uncontrolled airspace – Class G. There are a few Class G airspace areas, shown below in tan, mostly in the west. I can’t envision anyone having a great time flying in a little Class G patch.

GA aircraft don’t need to be ADS-B compliant until January 1, 2020. As we come closer to that date, we might start thinking about saving for the trip to the Avionics shop. I am not advocating that everyone run out and install the equipment this year, but I don’t recommend that you wait until December, 2019.  Can you imagine your Avionics Shop’s workload/backlog then? In the meantime, anyone who needs to replace a transponder would be a bit silly to choose anything but a Mode S capable unit, like the Garmin GTX 330.

If you decide to take advantage of ADS-B weather broadcasts now and purchase a Stratus or Clarity, take a look at the coverage map. If you fly in the areas currently without ADS-B coverage, you’ll find yourself a bit broken hearted. However, next year, the coverage will have improved significantly.  You can track NextGen and ADS-B progress at (requires Flash).


7 comments on “ADS-B – What Should You Know

  1. Glen Maxson says:

    Good article, and thanks for the link to my site at I’ve tried to compile everything a GA pilot might need to know about ADS-B to make an informed decison about when to equip,and what equipment options make sense based on where they intend to fly, equipment acquistion cost and installation tips. The site is in its infancy since there’s still much to learn about equipment choices and installation experience, but its a start and the site is kept current. For example, just added to the site is FAA’s progress report on NextGen.

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  3. Joe says:

    Overall, good article, but let me fill in some gaps.

    First, ADS-B will not be replacing radars anytime soon. The FAA plans to keep all long-range radars, but decommission many of the terminal short range radars at smaller airports after the 2020 ADS-B mandate goes into effect. The radars are needed as backup in case of GPS failure and for national security.

    1090ES also has ADS-B In but for only traffic (TIS-B)–no FIS-B. UAT can handle both traffic (TIS-B) and weather (FIS-B) on the ADS-B In feed. It should also be noted that the ADS-B traffic from both data links are crosslinked with the FAA’s ADS-R ground-based service–this allows aircraft with incompatible links to see each others targets on their cockpit display.

    As for the mandate, it does not require WAAS, but does require WAAS-like capability. For GA, WAAS is the obvious solution, but for commercial transport aircraft, there may be several alternatives in the future.

    Watch for several more GA ADS-B vendors entering the market this summer.

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