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Aireon space based ADS-B

RandyAB

Well Known Member
I sent a note to Garmin but I thought I would throw this out to the group I?m case others have insight or alternatively, a similar question. For the space based Aireon system that is going to be utilized in Canada for ADS-B, is the standard Garmin GTX transponder install going to allow for full functionality or is additional equipment needed? I see that Aireon says a top mounted antenna is required. Is this a need or is it just desirable? If necessary, i would like to do it now. My understanding is that the system mostly caters to commercial aircraft and that GA is an afterthought. Clarification?
 
I only find 2 current light GA type Diversity enabled transponders.

Good thread: http://forums.avidyne.com/diversity-antennas-for-transponders_topic1589.html

Says the Garmin GTX 330D (ES version) supports Diversity. Note the "D" in the hardware model.

L-3's Lynx 9000NGTD, "D" for diversity, or top and bottom antennae, lists for $6300 USD as an all in one solution. 1090ES out with WAAS built in, ADS-B In and Out.

I assume these 2 types would be the "hope" for a reasonable, existing solution assuming this becomes a Canadian mandate. Would possibly have to know if use of both antennae is constant and compliant with the needs of the OP space-based system.

The issue I see is I believe WRT ATC transponder/radar, the diversity is controlled to give best performance from air to GROUND. No idea what software or hardware makes Aireon "happy".

Large aircraft have had diversity for transponders with TCAS for at least a generation. I assume that the upper and lower antennae receive simultaneoulsy and the software controls reply transmissions directed to the stronger receiving antenna.

Just the S.W.A.G. of a pilot, not engineer or avionics guru. Walt?

ETA, Garmin FAQ leads to assuming they offer antennae diversity on some options. No idea about the other manufacturers.

https://www.garmin.com/us/intheair/ads-b/seven-questions/

"Why should I consider a dual (diversity) antenna installation for my ADS-B solution?
Antenna diversity technology configures your aircraft with both top- and bottom-mount antennas to reduce the potential for antenna “shading,” which helps prevent target drop out during turns and maneuvers. An optional top-mounted antenna also comes in handy during ground operations, when a bottom-mount mount antenna might not have clear line-of-sight to receive ADS-B ground station signals or transmissions from other participating aircraft."

The Aireon website does not even mention light GA.
https://aireon.com/resources/overview-materials/technical-specifications/
 
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An antenna mounted at a 45 degree angle to the longitudinal access and located on the 'stinger' position of the rudder would provide an almost 360x360 view of both ground and satellite stations.

Alternatively, if Microavionix would develop a dual mode ADS-B in + 1090es transponder for the stinger position, that would be ideal.
 
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Thanks for the info guys and especially the links Moose. I got a reply from Garmin who said that a single bottom mounted UHF was all that was needed but I'm thinking that this is specific to the US with their ground stations. I asked them to clarify if is was still applicable to satellite based ADS-B.
 
I sent an email to trig in the UK about this before purchasing a transponder. The response I got from them was that the waves can bend somewhat. The typical single mount transponder antenna if it is properly located (on the bottom of the fuselage behind the wing ) will work just fine. In Europe,diversity antenna is only required for larger aircraft where the waves would not bend enough for consistent coverage.
I purchased a trig tt22 and will be testing early this summer when my rv9a takes first flight.
Hope this helps

Jack
 
You'll certainly get a stronger signal to Aireon's satellite ADS-B receivers if you have a diversity transponder and an upper antenna. But they've released some early test data that show their receivers are sensitive enough to pick up ADS-B Out replies from aircraft with only a lower antenna.

Aireon's systems ride on Iridium Next satellites but no Iridium system is required on our airplanes...a 1090ES ADS-B Out transponder is all that's needed.

Dave
 
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Space Based vs US Ground Based ADS-B

Hello Gents

I just read the previous posts and it was very informative but just to make it clear, if I wanna operate in Canada and the US, what type of Transponder do I need...

I was planning to install a GDL-82 with my GTX-327 so that I could fly in the US next year but don't wanna install something costing $$$$ if I have to install another one to fly in Canada..

Do Garmin or someone else have a TXPR that work on 978MHZ & 1090 MHZ making it a single box for both country??

Makes you wonder why the US didn't go with a 1090 MHZ system from the start like the rest of the world...:rolleyes:

Thanks

Bruno
 
The US does run on 1090ES as well as UAT. The weather information is a UAT broadcast. Traffic is broadcast on either 1090 or UAT, depending on what the receiver can handle. 1090ES is the international standard and is required up in the flight levels.
 
A friend of mine is the ?payload specialist? ?payload manager? (not sure of title) for those Aieron satellites. Been with the Iridium stuff since the Motorola days. He?s all wired from two weeks prior to launch until after the bird is in orbit with a good self test. They started putting the ADS-B packages on the satellites starting n December 2017, I think. Ten satellites per launch. His Debonair has the Lynx Diversity unit and he?s testing the GA side on his airplane. Claims they can also send text and voice over the data stream, IIRC. I?ll check. All ov the oceanic tracks will go to this system. No more HF as primary. :) I?ll see what he says about the above. May take a day or two...

Tim
 
Bruno - at this stage in the game, for Canadian operators, I recommend installing a 1090ES solution. This brings many benefits in Canada and allows us to play in the US ADSB-mandate airspace if equipped with an appropriate position source to supply the full ADSB-out data stream.

Since this topic started out talking about Aireon, let's come back to that topic. I recommend 1090ES because Aireon has agreed to make available to national air service providers (NavCanada, for instance), upon request, last ADSB position/velocity data for an aircraft, typically an overdue aircraft. I see 1090ES as one more tool in my arsenal of tools to assist in Search and Rescue, should I ever need it.

While equipping with a UAT device will suffice for the US ADSB-OUT mandate, it brings zero benefits while flying in Canada. 1090ES brings benefit while flying in Canada and in the US. Makes the decision pretty much a no-brainer for me.
 
Bruno - at this stage in the game, for Canadian operators, I recommend installing a 1090ES solution. This brings many benefits in Canada and allows us to play in the US ADSB-mandate airspace if equipped with an appropriate position source to supply the full ADSB-out data stream.

Since this topic started out talking about Aireon, let's come back to that topic. I recommend 1090ES because Aireon has agreed to make available to national air service providers (NavCanada, for instance), upon request, last ADSB position/velocity data for an aircraft, typically an overdue aircraft. I see 1090ES as one more tool in my arsenal of tools to assist in Search and Rescue, should I ever need it.

While equipping with a UAT device will suffice for the US ADSB-OUT mandate, it brings zero benefits while flying in Canada. 1090ES brings benefit while flying in Canada and in the US. Makes the decision pretty much a no-brainer for me.

I think 1090ES generally should be a no brainer, especially for those of us outside the CONUS. I guess the question remains is how well a bottom mount antenna alone will work. Until it?s up and running I guess there is no telling for sure. I received a reply from a Garmin staring only bottom mount was necessary because the system is ground based. Obviously he didn?t read the part in my inquiry that specifically asked about the system outside the US that is based on satellite.
 
Dynon silence

I had posted a question about antenna diversity on dynon's forums about a month or so ago and got zero replies. The CAA will probably have to decide what the rules are first and then the avionics manufacturers will react.
 
Do Garmin or someone else have a TXPR that work on 978MHZ & 1090 MHZ making it a single box for both country??
I've installed a Garmin GTX-45R remote-mount transponder with my G3x system. It does ADS-B Out on 1090 MHz and receives ADS-B In on both 1090 and UAT. The GTX-345 is a panel-mount version of the same box.

With a 1090-transmit 1090/UAT-receive transponder you should be compatible everywhere 1090 is required but still be able to get the benefits of FIS-B weather products when you're in the US. An added benefit in the US is that you don't have to carry two transponders as the FAA still requires us to have ATCRBS Mode A/C capability. A 1090 ADS-B transponder is (or should be) backward-compatible with Mode A/C, but using UAT for ADS-B Out means keeping a separate ATCRBS box.

HTH

Dave
 
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I was told a few days ago by an avionics shopthat the 345 doesn?t support diversity. You have check each model to determine if it would. He also mentioned that Garmin doesn?t offer a top antenna yet.

uAvionix at Copperstate mentioned that a recent meeting with Nav Canada & TC stated adsb is mandated for operators over 18000ft but (at this time) don?t have plans to mandate GA below 18000ft.

The general situation seems pretty murky in Canada and I?m still inclined to continue to use legacy equipment and find the cheapest effective adsb in/out add on to comply when travelling south.
 
Hello Gents

Do Garmin or someone else have a TXPR that work on 978MHZ & 1090 MHZ making it a single box for both country??

Makes you wonder why the US didn't go with a 1090 MHZ system from the start like the rest of the world...:rolleyes:

Thanks

Bruno

The situation is complicated. The FAA designers feared frequency congestion if everyone was on one frequency. So they mandated 1090 over 18,000?. That essentially forces the airlines to 1090. For below 18,000? you have a choice of 1090 or 978. The designers *thought* 978 (UAT) would be less expensive so GA would go that route, and they?d end up with a 50-50 split. It has not worked out exactly that way, I believe there are more aircraft on 1090. For ADSB-in, there are many receivers that listen on both frequencies. If you have a single frequency receiver, then you must rely on receiving a ground station to get the traffic on the other frequency. For ADSB-out, the FAA has mandated that you may not use both frequencies (that would defeat the purpose), you have to choose one.
 
I was told a few days ago by an avionics shopthat the 345 doesn’t support diversity. You have check each model to determine if it would. He also mentioned that Garmin doesn’t offer a top antenna yet.
That's correct, it doesn't. Diversity isn't required in the US for the ADS-B transponder class specified for light GA, even when used above 18,000 feet.

There's no ADS-B mandate yet in Canada (Canadian folks correct me if I'm wrong) so by definition there should be no *requirement* as of now for diversity on 1090. Whether or not it'll be required if/when Nav Canada goes to Aireon for ADS-B information is a question for Transport Canada.

More info here - https://www.aopa.org/news-and-media/all-news/2016/january/pilot/pe_adsb

Dave
 
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