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Trig 22 vs Dynon SV-XPNDR-261 Mode-S Transponder

Aiki_Aviator

Well Known Member
Hi all,

I am in the final throws of my panel and I have hit a technical stumbling block.

I have been looking into the Trig-22 and thought basically it was the bees knees, however, I have now stumbled onto the SV-XPNDR-261 Mode-S Transponder.

Apart from the fact that it is a remote transponder I can't see if there are any other differences.

My research suggests that the Trig 22 has an inbuilt Altitude encoder, however, I am not sure about the SV-XPNDR-261 as it states it required a WAAS capable GPS to ensure full compliance come 2020 ADS-B requirements, and it doesn't say that it has a built in encoder.

Could someone shed some/any light on this as my panel will either have a cut-out or it won't and the space can be better used :)

Thanks in advance.
 
The Dynon Skyview will control the SV-261, altitude data will come from the Skyview.

The Trig TT-22 requires the TC 20 controller (remote head unit) for operation. The TC20 has a built in altitude encoder.

Both the SV-261 and the TT-22 are ADS-B compliant transponders that will accept GPS data to compy with future ADS-B requirements.
 
Follow-up

Hi Walt,

Thanks for the info, just to clarify, what is your understanding of the Altitude encoders function on the head unit; what is the benefit, given the Dynon unit does not have one.

Why would the Trig-22 require a GPS unit to become compliant.

Nothing on the Trig site suggrests a need for a GPS unit to be compliant.

Sorry, bit confused.

Andrew.
 
Andrew -

All ES equipped mode-s transponders require a certified WAAS GPS position input for 2020 FAA compliant ADS-B OUT functionality. Without a GPS connection ADS-B OUT will not function. The Dynon xpdr has two connections for GPS input. One is via its serial connection to the SkyView allowing the Skyview GPS to provide position information (non-compliant however) and a dedicated GPs input connection for 3rd party GPS (compliant or otherwise).

The dynon transponder does not require an altitude encoder because as Walt pointed out, altitude information is provided by the Skyview Display via the serial connection.
 
Why would the Trig-22 require a GPS unit to become compliant.

Nothing on the Trig site suggrests a need for a GPS unit to be compliant.

Sorry, bit confused.

Andrew.

Andrew,

Because a transponder without a GPS has no idea where it is and how fast it is traveling and in what 3D direction it is moving and that is the primary purpose of ADS-B out....
 
No WAAS in Oz

Hi Guys,

Unfortunately, there is no WAAS in Australia nor will there be. Therefore I am concerned as to how it will satisfy the 2020 ADS-B mandate if a WAAS certified GPS is required. Presuming Australia goes the same way as US, but without a WAAS system.

So if I paraphrase, the Trig 22 can provide a certified altitude from the head unit, whereas the Dynon unit cannot.
The Dynon unit gets its Altitude info from the Skyview system.
Both units will require Certified GPS inputs to comply with ADS-B requirements, however, not necessarily WAAS enabled for lateral position and speed.

Does this sound right as it would apply to Oz?

Sorry bit late here in Oz. Hope I am making sense.
 
I think this decision should boil down to whether you have a Skyview display or not. If you do, why would you want to clutter your panel with a control head when you have the Skyview? As mentioned, the encoder becomes a non-issue. While a GTX-327/330 gives easier access to squawk codes, the Skyview gives you automatic mode changing between flight and ground and you can easily see the status of the transponder in the screen you are always looking at. After flying behind the G900X for 50 hours or so, the more I can see and control via my Skyview the better I like it.
 
For the Trig, what would be a suitable GPS for it, to be mounted on the avionics shelf?

Dave

From the Trig Installation Manual:

12.2 FAA 91.227 Compliance
The TT22 transponder can be connected to the following GPS units to form the basis of a 14 CFR 91.227 compliant ADS-B installation:
 Freeflight 1201 & 1204 WAAS/GPS Sensors
 NexNav MINI & NexNav MAX WAAS/GPS Sensors
 Garmin GNS 400W/500W series
For installations seeking certification to 91.227 or other applicable standards, additional compliance information is available on request from Trig Avionics Limited.
 
For the Trig, what would be a suitable GPS for it, to be mounted on the avionics shelf?

Dave

Depends on if you want or need to become a fully compliant client for the ADS-B ground stations.

For now the FAA is allowing non compliant clients to wake up the ground stations.

To be a fully compliant client, you need a supported gps connected that meets the requirements of FAR 91.277/AC 20-165. Trig will tell you what is supported.

If you don't want or need to be fully compliant, you need whatever Trig supports that fills out enough of the ES data set to wake up the ground stations. you will need to ask them what that might be...
 
Last edited:
This is a customer in Australia, so let's be careful to not focus on FAA requirements too much. Australia has very different rules and mandates. They have no UAT or ground stations, they are more like Europe where everything is 1090MHz air to air, and their requirements for certified position sources are not as strict as ours.

First, on the transponder, Trig vs Dynon:

The Dynon transponder only works with a SkyView, so if you don't have a SkyView, it isn't an option. If you do, this uses the non-certified altitude encoder that is in SkyView. CASA is fine with this configuration in an experimental. You control the transponder with menus on SkyView.

The Trig transponder has it's own control head and in that is a certified encoder. If you get this and have a SKyView, there is no way to connect the two together.

That's where the differences end. Your requirements for hooking a GPS up are identical from there.

AUS has a 2014 Mode-S mandate, but both of these are Mode-S transponders, so you will have no issues there.

AUS has a 2017 ADS-B mandate, but only for IFR craft. If you want to meet this mandate, you will need a certified GPS in the plane. AUS's requirements for a certified GPS are not as stiff as the USA, but you still need one. As you mention, they don't have WASS there, but even in the USA, it's not WASS you need technically, it's a certain certification level.

If you are not IFR, AUS actually encourages you to use a non-certified GPS and broadcast your position, as long as the various ADS-B out bits are set right. If you are using the SkyView system, this all happens automatically for you using the SkyView GPS.

If you want a good contact in AUS that knows a lot more about this than me, send me a PM and I can give you his name.

--Ian Jordan
Dynon Avionics
 
Mouldy Oldie

I have a heritage RV12 and ordered the European avionics kit with the Dynon SV-XPNDR-261 Mode S transponder. The transponder received with the kit is a Trig TT22. I can only assume they are one and the same???
 
The Dynon transponder is made by Trig, and it is almost the same as the TT22. However, the two are not directly interchangeable. Software, I think(!).
 
Air Services Australia ADS-B FAQ

Hi Andrew,

Google search 'Air Services Australia ADS-B FAQ'.

The document should be titled 'Questions and Answers for Owners of Australian General Aviation Aircraft'. V 2.2 dated Dec 2016.

Lots of relevant information in there and will exactly answer your questions.
 
One important detail has heretofore been missed in this conversation...

The Trig TT22 transponder often uses the TC20 control head to provide both control over transponder functions as well as altitude encoding. This is what I have in my aircraft as a stand-alone 1090S/ES system. It is being fed position by a certified WAAS navigator, thus meets US ADSB-Out requirements.

BUT that's only one way of making things work.

If one is installing an EFIS, the newer GRT Avionics EFIS products contain a built-in pair of serial communications ports (one transmit, one receive) which interface directly with the Trig TT22 transponder. This allows the EFIS to become both the controller for the transponder as well as its source of altitude information. In this manner the GRT EFIS / TRIG TT22 combination behaves like the Dynon Skyview EFIS / SV transponder combination.

Add a GRT Safe-Fly 2020 GPS receiver to the package as a position source and you have a US-mandate-compliant ADSB-Out solution for not a huge amount of money.

If one were considering updating a "steam gauge" instrument panel to include a Mode S/ES transponder, adding a GRT Mini EFIS would get you a means of controlling the remote-mount transponder, a means of providing altitude data to the transponder, as well as a fully-loaded EFIS in a small and relatively inexpensive package.
 
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