Garmins New ADS-B: All-In-One Transponders

As our refreshed ADS-B buyer’s guide on page 7 proves, there is no shortage of ADS-B In and Out solutions. But, what has been missing is a certified WAAS-equipped ADS-B system packaged in a rack-mounted transponder that works with OEM glass panels, retrofit displays, portable GPS and tablet computers. That’s a void Garmin plans to fill with its next-generation wireless ADS-B transponders—the GTX335 and GTX345.

Several years ago when it was looking like FAA-mandated ADS-B equipage was a sure thing, buyers logically envisioned an easy path to compliance with a transponder. That came early on with Garmin’s upgradable GTX330. But it was only a partial solution. It outputted ADS-B, but couldn’t receive the free FIS-B weather everyone wants. It also required a pricey WAAS GPS input (which meant a $10,000-plus GNS navigator upgrade) to complete the ADS-B output data. That didn’t help owners of lesser, non-WAAS-equipped aircraft. Let’s have a look at Garmin’s latest GTX.

Familiar Face

The new transponders are based on a design Garmin has been using for years, beginning with the Mode A/C digital GTX327 transponder. If you have the GTX327 or the later GTX330, you’ll be hard-pressed to tell any difference between them and the new GTX335/GTX345 models. The new ones retain a flight timer and pressure altitude readout.

Garmin offers the new ADS-B transponder in several versions; the most basic is the entry-level GTX335 ES without GPS. At $2995, it has 1090ES extended squitter ADS-B Out, but no ADS-B In. If you think this entry-level model sounds a lot like Garmin’s previous GTX330ES, you are correct. Garmin says there is little if any significant difference between the two, other than the GTX335 having a lower price—nearly $1000 less.

While the GTX330ES will be replaced by the GTX335, Garmin made it clear that it can support the GTX330ES series for years to come. That makes sense, since the new models are based on the existing GTX330-series platform.

The GTX335 is available with internal WAAS GPS as an option, which meets the ADS-B mandate standard for a position source and increases the price to $3795. This means you won’t have to install a panel-mounted GPS to drive the transponder. The shop will have to install a GPS antenna, of course, and the transponder will need a traditional L-band antenna system like any transponder.

The $4995 GTX345 series kicks the interface potential up to a higher level with a dual-band ADS-B In receiver. Dual bands mean the transponder can receive ADS-B data on both 978 and 1090 MHz frequencies. Like the GTX335, the GTX345 is a 1090ES unit, making it a player for higher altitudes where 1090ES is required. The flagship GTX345 with internal WAAS GPS is $5795.

Bluetooth Enabled

A major difference between the GTX345 and lower-end GTX335 is the internal wireless Bluetooth transceiver, which follows the footsteps of Garmin’s remote-mounted Flight Stream wireless hub. Using Garmin’s Connext Bluetooth link, the GTX345 streams ADS-B traffic and FIS-B weather data to the aera795/796 portable GPS, iOS and Android tablets running the Garmin Pilot navigation app, in addition to the ForeFlight Mobile app for iPad.

The data interface trickles down from the Flight Stream two-way data transfer protocol (it’s only a one-way communication stream between the transponder and tablet app) and it enables the transfer of pressure altitude data, ADS-B messaging, plus FIS-B weather and ADS-B traffic overlay. You’ll need to have ForeFlight Mobile version 7.20 or higher for the interface to work, while the ADS-B In data interface isn’t limited to portable equipment.

Through a wired interface, the GTX345 sends both ADS-B weather and traffic to the GTN750 and GTN650 navigators, and to the GNS530W and GNS430W WAAS navigators.

As with the older GTX33-series remote transponder, the GTX345 is available in a remote LRU version, the GTX345-R. This enables the GTN750 to display and provide tuning of transponder squawk codes and mode functions, eliminating the need for a panel control head.

But don’t expect the same functionality with all displays. For example, the GTN750 and GTN650 can display up to 60 ADS-B airborne and ground traffic targets in true ADS-B symbology. As for FIS-B weather, the GTN750 will display regional and CONUS NEXRAD, METARs, TAFs, PIREPs, winds and temperature aloft, AIRMETs, SIGMETs, TFRs and NOTAMs. That’s pretty much a full-boat ADS-B interface. There is also Garmin’s TargetTrend function—advanced traffic awareness that portrays the traffic on-screen in real and future time.

The GNS530W and GNS430W interface is somewhat limited. For example, these displays will only support eight airborne traffic targets displayed in TIS-A symbology. As for FIS-B weather, you’ll see regional and CONUS NEXRAD, METARs and TAFs. Additionally, you won’t be able to control the remote GTX345-R.

The GTX345 will also work with Garmin’s stand-alone GMX200 MFD, displaying up to 60 traffic targets, plus regional NEXRAD, TAFs and METARs. It will also work with the long- discontinued MX20, but out experience is the unit just doesn’t have the processing horsepower to deal with weather graphics—potentially shutting down or freezing up when you need it the most.

Garmin says an interface with the G600/G500 PFD is planned for a future release, displaying all of the traffic and weather products that the GTN navigators are capable of.

G1000 Interface

ADS-B In capability has been a nagging shortcoming of Garmin’s G1000 integrated avionics suite, and the GTX345 finally enables the capability. The GTX345-R can take the place of the existing remote GTX transponder in select G1000 systems.

For most G1000s, the $5795 GTX345-R with internal GPS is used—requiring another antenna. It would be easier to use the existing G1000 WAAS LRU to drive the transponder, but it requires OEM approval. The GTX345-R can display FIS-B weather and ADS-B traffic on some G1000 systems, including non-WAAS suites in Cessna 172, 182, 206, 208 Caravan and 350/400 Corvalis singles. It’s also fully compatible with G1000-equipped Piper models, including the Meridian turboprop.

Display of GTX345-R ADS-B traffic on any G1000 requires GDU software version 7.10 and GIA63 version 5.31 or later. For FIS-B weather display, any G1000 suite requires GDU software version 12.00 and GIA63 version 6.20 or later. Check with your G1000 service center on upgrade costs and OEM approval status of the software. Some aren’t approved yet, including the Diamond DA40NG and DA42. The Hawker Beechcraft G58, G36 and some G1000 Mooney models aren’t approved, either.

Competition, New Altitude Encoder

Garmin isn’t alone with a transponder-based total ADS-B solution. Appareo is working on its Stratux ESG GPS-equipped model, but the new GTX series is certified and available now. Another model that’s in the works is the $3500 Sandia Aerospace STX360 Sentinel. Sandia says it will be available in a remote LRU for interfacing with EFIS displays.

Unlike the Garmin and Appareo 1090ES solutions, it won’t be a player in high-flying aircraft since it outputs ADS-B on 978 MHz. While it also receives ADS-B In on 978 MHz, it won’t display NEXRAD graphics on its LCD display (only METARs) and it doesn’t have an internal WAAS GPS receiver. It does have a wireless transceiver for outputting FIS-B and ADS-B traffic to a tablet, but Sandia hasn’t announced app compatibility. Sandia says it’s on track for certification later this year.

In our estimation, that leaves L-3 Aviation, with its Lynx NGT9000 multi-function transponder, the closest certified competitor to the GTX345. We covered the NGT9000—which starts at $6800—in the April 2015 issue of Aviation Consumer and liked its scalability, bright RGB touch display and intuitive feature set. It doesn’t have an internal wireless transceiver, so you’ll have to purchase an optional module to stream the data to tablets running the WingX Pro navigation app. The flagship NGT9000D+, which has diversity, internal WAAS GPS, plus an internal TAS traffic processor, has an eye-popping price tag of nearly $12,000.

Garmin has also introduced its next-generation Mode C altitude encoder, simply called the Garmin Altitude Encoder. At $279, it’s the smallest digitizer we’ve seen to date and cuts down on installation effort because it mounts directly to the GTX345/335 mounting tray. Garmin says the encoder has a proprietary data code that works directly with the GTX335/345 transponders. You still need Mode C altitude encoding in a full-up ADS-B interface.

While manufacturers like Sandia Aerospace (which previously supplied Garmin with its SAE-series digitizer) have conveniently integrated the encoder into the transponder, there is a downside: The static system has to be recertified if the transponder is removed and reinstalled.

No doubt, buyers who recently invested in Garmin’s GDL88 remote ADS-B solution are shaking heads at Garmin’s new transponder technology, which promises an easier, cheaper and cleaner installation. But, that’s the cost of early adoption in a rapidly changing ADS-B market.

Mandate-Compliant Panel ADS-B Products

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