What’s the difference between 1090 and 978?

You probably know by now that most airplanes will have to be equipped with ADS-B Out by 2020 in order to meet the FAA mandate. Beyond that basic issue, though, there are still a lot of questions to consider. One of the first is 1090 vs. 978. That is, should you install an ADS-B Out transponder that works on the 1090 MHz frequency (sometimes called 1090ES) or the 978 MHz frequency (sometimes called a 978 UAT)?

There is no simple answer, and all ADS-B Out transponders perform the same basic function no matter what frequency they use. Both meet the 2020 requirement. But there are some important differences to consider, depending on the type of airplane you fly.

  • What is the total installed cost? The cost of ADS-B Out hardware is only one part of the equation – be sure to ask about the installation time and cost as well. 1090ES transponders are mounted in the avionics stack, in place of an existing Mode C transponder, so they don’t require the removal of the interior like most 978 installations (which are typically mounted in the tail of the airplane). In many cases, the installation cost is 30-50% less for a 1090 solution.
  • How old is your Mode C transponder? In addition to ADS-B Out, you’ll still need to have a traditional transponder after 2020. If your existing Mode C transponder is on its last legs, a 1090ES transponder is probably the right answer, since it checks both boxes. In addition to meeting the mandate, you’ll get the features of a new transponder, like a clear digital display, push-button code entry and a dedicated VFR button. 978 requires you to maintain your existing Mode C transponder, so if you already have a new one you may be able to save money with a UAT.
  • How integrated is each solution? Some 978 UAT transponders require separate control heads to synchronize the squawk code with your existing Mode C transponder – or even a separate panel-mounted indicator light. 1090ES solutions are integrated solutions: simply connect it to your existing transponder antenna and altitude encoder, then add a WAAS GPS antenna if a built-in GPS is included. The one exception is Garmin’s GDL88/84, 978 solutions that automatically sync with your Mode C transponder.
  • Do you fly internationally? 978 UAT transponders are limited to use in the United States, so pilots traveling to Canada, Mexico or the Caribbean should choose a 1090ES transponder.
  • Do you fly above 18,000 ft.? Aircraft equipped with 1090ES transponders are authorized to fly at all altitudes, whereas 978 UAT transponders are not permitted above 18,000 ft.
  • What multi-function display do you have? If you have a glass cockpit or a modern navigator, a 978 UAT can display subscription-free weather and traffic on those beautiful color screen (if your 978 solution is an ADS-B In model in addition to Out). If you already receive weather and traffic with a portable ADS-B receiver, you can probably save some money by just choosing Out.


Mac McClellan, writing in EAA Sport Aviation, sums it up well: “If you plan to keep your airplane much beyond 2020, I think the new transponder route makes a great deal more sense… the 1090ES transponder install requires half the new antennas, no new cockpit panel unit, and a fraction of the wires.” On the other hand, if you have a glass panel, a remote-mounted 978 unit may make a lot more sense – especially if it’s done as part of a larger avionics upgrade.

Whichever ADS-B Out solution you choose, be sure to focus on the total installed cost of your new avionics. Read the fine print and ask informed questions about labor costs to install your new transponder and any additional parts that may be required. The right answer for you is the package that meets the 2020 ADS-B mandate, offers the upgrades your airplane needs, and is affordable to install.

Appareo Stratus ESG

For too long, ADS-B has been expensive and complicated. Not any more. The company that revolutionized ADS-B In with the Stratus series of portable weather receivers has done it again. Meet Stratus ESG, the all-in-on ADS-B Out solution.

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Appareo Stratus ESG

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The affordable, all-in-one ADS-B Out solution

For too long, ADS-B has been expensive and complicated. Not any more. The company that revolutionized ADS-B In with the Stratus series of portable weather receivers has done it again. Meet Stratus ESG, the affordable, all-in-one answer for adding ADS-B Out to your panel.


  • ADS-B Out transponder meets the FAA mandate
  • 1090ES technology – no altitude or geographic limitations
  • Integrated WAAS GPS for an all-in-one solution – nothing extra to buy
  • Includes new Mode C transponder – upgrade your old analog transponder
  • Fits in standard transponder slots – typically 50% less to install than 978 models
  • All mounting hardware and antennas included

Connect to your Stratus portable

In addition to being a great transponder and an ADS-B Out solution, Stratus ESG can also connect to a Stratus portable ADS-B In receiver. This makes it a complete system, with subscription-free weather and traffic.

  • Get a complete traffic picture in ForeFlight
  • Better ADS-B reception
  • Better GPS reception
  • Full-time power source
  • Works with Stratus 2, 1S and 2S

Stratus ESG is made in the USA and includes a 2 year warranty.

For pilots who already have a WAAS GPS in the panel, Appareo also offers Stratus ES with the same features minus the GPS receiver.

Garmin GDL 84

gdl 84 twoAffordable, Stand-alone ADS-B “Out/In” Solution

  • Dual-link solution meets U.S. ADS-B “Out” requirements
  • Displays subscription-free ADS-B weather and datalink traffic on your iPad® or other compatible products
  • Packaged with Flight Stream™ 110 or 210 device for wireless connectivity with tablets/mobile devices via Garmin Connext™
  • Built-in SBAS/WAAS GPS receiver
  • Supports patent-pending TargetTrend traffic and SURF display

For U.S. aircraft owners seeking an easy, cost-efficient way to meet the requirements for ADS-B “Out” equipage – while enjoying the “In” benefits of subscription-free weather and traffic – the Garmin GDL 84 offers the ideal solution.

This is Do-it-all ADS-B

Under the provisions for NextGen ATC implementation, all aircraft operating in controlled U.S. airspace will need to be equipped with Automatic Dependent Surveillance – Broadcast (ADS-B) “Out” technology before end-of-year 2019. The GDL 84 offers a smart, all-inclusive installed solution for the many GA pilots who operate below Class A airspace (18,000 feet) in the U.S.

Dual-link Means Complete Air-to-air Coverage

Using its built-in WAAS GPS receiver, the GDL 84 generates precise information about your aircraft’s position, track and ground speed. It then broadcasts this information to the ADS-B ground station network for relay to ATC and other ADS-B “In” equipped aircraft in the airspace. The dual-link (1090 MHz and 978 MHz) frequency reception capability of the GDL 84 enables it to receive air-to-air position reports directly from other aircraft, so you can always see those ADS-B broadcasting aircraft in your vicinity, regardless of which datalink frequency they’re using. Accessing both of the available ADS-B frequencies used in the U.S. system, your GDL 84 ensures a more complete situational picture – for added confidence in all phases of flight.

Stream Weather and Traffic to Your iPad

The GDL 84 package doesn’t depend on an installed display to provide the benefits of ADS-B “In” to your cockpit. With its included Flight Stream wireless gateway device, the GDL 84 works to keep your NextGen compliance costs low, while providing the means to uplink and display subscription-free U.S. ADS-B weather and traffic on your Garmin Pilot™ equipped iPad or other compatible mobile device. On the weather side, you can view animated NEXRAD imagery, METARs, TAFs, winds and temperatures aloft, PIREPs, NOTAMs and more. Plus, on the traffic side, your tablet can display moving target symbols and alerts to help you recognize any potential conflict scenarios in busy airspace.

Access More Advanced Capabilities

In addition to audible target alerts (“Traffic. Two o’clock. High. Two miles.”) the GDL 84 will also support the latest in ADS-B traffic display capabilities, which can be viewed with the Garmin Pilot app on your iPad or other compatible tablet. Our patent-pending TargetTrend relative motion tracking technology, for example, offers a faster, more intuitive way of judging aircraft trajectories and closure rates in relation to your aircraft’s flight path. Likewise, in the airport environment, Garmin SURF technology works with SafeTaxi® to support geo-referenced display of ADS-B-equipped targets, including taxiing aircraft and ground service vehicles, on the surface diagram.

Single-entry Squawk Code

The NextGen equipage rules require your ADS-B “Out” source must be able to squawk the same code as your transponder. The GDL 84 has the ability to automatically synchronize with your onboard transponder for its squawk code, and then transmit that data through its own datalink. Not only does this provide a single point of data entry for ADS-B “Out”, but it also allows you to meet the new regulations without the need for expensive control system or transponder upgrades. Thus, GDL 84 works in the background to make code entry fast and easy – while helping to make your path to ADS-B compliance as simple, straightforward and cost-effective as possible.

You Can Grow From Here

As the NextGen airspace system evolves, you may find that you want to add ADS-B weather and traffic interface capabilities to an MFD or other navigation display onboard your aircraft. While the GDL 84 is designed for use with compatible tablets and smart devices only, Garmin does offer an easy growth path to installed-system display capability. For a minimal cost, your GDL 84 can be returned to Garmin for factory upgrade to a GDL 88 configuration. With this upgrade, your receiver can bring all the graphical benefits of ADS-B to your in-panel Garmin flight displays.

S-TEC Autopilots

S-TEC is the world leader in analog and digital autopilot systems. With the industry’s largest selection of single-axis, primary two-axis, and full-function two-axis autopilots, you’ll experience smoother, more stable flight and reduced maintenance down-time. S-TEC autopilots are STC’d for over 1,200 fixed wing aircraft models, and are installed on more than 35,000 aircraft worldwide.
Genesys special

Garmin GTX 330ES

gtx330 270x200Surveillance for Busy Airspace

  • IFR-certified 250 W transponder
  • Optional 1090 MHz ES broadcast technology
  • Easy-to-read LCD display
  • Traffic Information System (TIS-A) alerts on compatible displays
  • Pressure altitude, dedicated VFR squawk button and more

A panel-mounted Mode S digital transponder series with traffic datalink capability and dedicated pushbutton keys for squawk code selection, the GTX 330 family brings ATC aircraft surveillance to new levels of precision, reliability and performance.

Leading the Way to ADS-B with Optional ES Upgrade

Optionally available with available ES, or Extended Squitter, technology the GTX 330 takes the lead in providing an affordable pathway to ADS-B compliance for the Next Generation airspace system. Using precise GPS-referenced positioning information, the extended squitter technology enables transponders to automatically transmit more accurate, and more useful, traffic surveillance data — including aircraft flight ID, position, altitude, velocity, climb/descent, and heading information. (Compared to traditional Mode S and Mode C transponders, which can only broadcast altitude, and thus require ground-based radar to correlate and identify the aircraft’s position.)

Traffic in Simulcast

Certified to TSO-C166b authorization for 1090 MHz extended squitter transmission, the ES upgrade improves upon the existing transponder query system while working seamlessly with existing ATC protocols. The ADS-B reports provide ground controllers with considerably faster updates than traditional radar. And by simultaneously broadcasting this information to TAS or TCAS equipped aircraft, it enables them to essentially see the same traffic picture for their location that ATC is watching on the ground. Thus, with everyone in the ADS-B loop watching and reacting to the same flight trajectories, safe separation is far easier to maintain.

Quality Shows Through

All the features of the standard GTX 330 transponder are retained in the ES version: Solid-state design, 250-watt transmitter, remote ident and auto standby, altitude monitor with voice alerts, TIS-A traffic interface, and an easy-to-read LCD display that reverses its numbers out of black for optimal viewing in all lighting conditions. A dedicated VFR squawk code button makes entering the numbers quick and easy. And a variety of useful timing and display functions include flight time, count-up and count-down timers, plus current pressure altitude. The GTX 330 can also be used to satisfy the European mandate for Mode S level 2 surveillance. And an antenna diversity option is added with the GTX 330D for improved air-to-air surveillance of TCAS-equipped aircraft flying above you.

Garmin GDL 88


Get ADS-B Benefits Today

  • Dual-link Universal Access Transceiver (UAT)
  • ADS-B “Out” solution for many aircraft
  • Receives subscription-free weather and datalink traffic
  • Optional SBAS/WAAS GPS
  • Approved for installation in hundreds of aircraft models

The GDL 88 is the first dual-link solution for certified aircraft that not only provides a path to ADS-B “Out” compliance for many pilots, but also brings subscription-free weather and advanced traffic display to the cockpit.

Satisfy the ADS-B Mandate

Under the NextGen air traffic management system, all aircraft in controlled airspace will need to be equipped with ADS-B “Out” technology by 2020. For those who only fly below Class A airspace (18,000 ft) and in U.S. skies, the GDL 88 offers an affordable solution to reaching compliance. And even if you fly above 18,000 ft, the GDL 88 can still give you all the benefits of ADS-B “In” data – consider pairing it with a GTX 330/33 ES transponder for a comprehensive ADS-B “In/Out” solution.

With ADS-B “Out”, the GDL 88 gathers information about your position, track and ground speed from either your existing WAAS GPS source or an optional built-in WAAS receiver. It then broadcasts this information to ADS-B ground stations over the 978 MHz Universal Access Transceiver (UAT) frequencies. This gives ATC and ADS-B “In” equipped aircraft a more precise picture of what’s happening in the sky, and allows for more safe and efficient flight routing.

Access Aviation Weather

The GDL 88 also features ADS-B “In” datalink technology that allows it to receive subscription-free Flight Information Service-Broadcast (FIS-B) weather broadcast from ADS-B ground stations on this same 978 UAT frequency. On a compatible flight display, this uplink allows you to view graphical NEXRAD radar, METARs, TAFs, SIGMETs, AIRMETs, NOTAMs, TFRs and more.

Spot Potential Traffic Threats

The GDL 88 can receive ADS-B position reports directly from other aircraft in your vicinity. Because the FAA permits ADS-B broadcasts on 2 frequencies (978 UAT and 1090 ES), the GDL 88 contains both receivers so you can see a comprehensive view of all ADS-B “Out” equipped targets. ADS-B provides the ability to provide air-to-air datalinks with other aircraft. The GDL 88 is compatible with active traffic systems and prioritizes multiple traffic inputs, removing duplicate targets by choosing the highest integrity source available.

ADS-B “In” technology also allows the GDL 88 to receive Traffic Information Service-Broadcast (TIS-B) information. On a compatible display, TIS-B allows you to view the same dynamic traffic picture that ATC ground controllers are seeing.

Take Advantage of Advanced Display Capabilities

Advanced Display Capabilities

TargetTrend™ technology (available on compatible displays) provides an easy-to-interpret picture of aircraft trajectories. When receiving ADS-B traffic information, this allows you to better predict potential conflicts. SURF technology also supports the display of ADS-B-equipped surface targets on Garmin SafeTaxi® airport diagrams – including taxiing aircraft and ground vehicles.

The advanced display capability of the GTN series avionics allows for enhanced functionality with the GDL 88. When there are several traffic targets in an area, the GTN will declutter the display by grouping the targets and showing only the one that is the highest priority. The pilot can touch a grouped target to ungroup and show all targets in the area. The GTN also allows the pilot to select any target on the display to view more detailed information including closure rate and ground speed.

Receive Traffic Alerts

You can still take advantage of the GDL 88’s ADS-B “In” traffic, even if you don’t have a compatible flight display to view the data. When installed in an aircraft without a compatible display, a visual indicator light can alert you when traffic enters your vicinity. Audible alerts tell of a target’s range, bearing and relative altitude (when available). You’ll hear this information through your cabin audio system in an ATC-like spoken format. For example, you might hear, “Traffic: 10 O’Clock, High or Low or Same Altitude, 2 miles.” In most cases, installing a GDL 88 with WAAS can provide a complete solution for ADS-B “Out” while still allowing you to receive some ADS-B “In” benefit — all with a single product.

Avoid Upgrading More Than You Have To

ADS-B requires your ADS-B “Out” source must squawk the same code as your transponder. Patent-pending technology allows the GDL 88 to be compatible with a wide range of general aviation transponders — synchronizing squawk code and ident to eliminate the need to install a dedicated UAT control panel.

Enhance Your Reception

Available antenna options allow the performance of the GDL 88 to be optimized for any type of aircraft. For optimal performance, a diversity antenna version with both top- and bottom-mounted antennas enhance the detection of traffic both above and below, and works to minimize radio blind spots caused by the wings or fuselage during aircraft maneuvering. This is especially useful in maintaining optimal reception of ADS-B weather and traffic during ground operations. A basic bottom-mount antenna version is also available as a more cost-effective alternative.

Aspen ATX200G

AtX200G-single-product-feature (1)Aspen’s ATX200G dual-band in, 978 MHz out ADS-B transceiver + GPS is a solution for aircraft that have a Mode A/C transponder (or Mode S without Extended Squitter) and no ADS-B compatible GPS installed. The ATX200G is a certified solution and is compatible with Aspen Evolution PFDs and MFDs.

System benefits:

Access to ADS-B subscription-free weather and traffic for your Aspen display.

Meeting the FAA ADS-B out mandate with this solution*:

With your existing Mode A/C transponder (or Mode S without ES) installed, plus the ATX200G, you will meet the mandate below 18,000’.

*Note: Although an unlikely combination, if your aircraft has a Mode S with ES transponder and no WAAS GPS installed, the ATX200G meets the ADS-B compatible GPS requirement. In this scenario you would meet the mandate at any altitude.

Aspen ATX200

AtX200-single-product-featureAspen’s ATX200 dual-band in, 978 MHz out ADS-B transceiver is a solution for aircraft that have a Mode A/C transponder (or Mode S without Extended Squitter) and a WAAS-enabled GPS installed. The ATX200 is a certified solution and is compatible with Aspen Evolution PFDs and MFDs.

System benefits:

Access to subscription-free ADS-B weather and traffic for your Aspen display.

Meeting the FAA ADS-B out mandate with this solution:

With your existing Mode A/C transponder (or Mode S without ES) and WAAS GPS equipment installed, plus the ATX200, you will meet the mandate below 18,000’.

Aspen ARX100

ARX100-single-product-feature-1Aspen’s ARX100 dual-band ADS-B receiver is a solution for aircraft that already have a Mode S transponder with Extended Squitter (ES) and a WAAS-enabled GPS installed. The ARX100 is a certified ADS-B weather and traffic In solution and is compatible with Aspen Evolution PFDs and MFDs.

System Benefits:

Access to ADS-B subscription-free weather and traffic for your Aspen display.

Meeting the FAA ADS-B out mandate with this solution:

With your existing Mode S with ES transponder and WAAS GPS, you meet the mandate at any altitude.