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ADSb HELP!

RV8iator

Well Known Member
Benefactor
I'm at my wits end trying to figure this out and need your collective help.

I'm running a Trig 31 transponder, ACK 30.5 encoder, Garmin 496 GPS, ( I know it's not 2020 compliant, but many others are running this and it works), Skyradar D2, and running WingX Pro. The only uncommon denominator between several working setups and mine is the ACK30.5 encoder. It's brand new and works as far as ATC can see.

All the settings have been verified with Trig and others that are using similar setups. The boxes are talking to each other.

The altitude on the face of the Trig and what ATC see's is correct. The ADS altitude that I put out is wrong and jumps around on WingX. All other indications are correct from other planes in the area.

My big question is where does the Trig get the altitude it sends out for ADS, and, how can it be sending out and indicating the correct altitude to ATC but the wrong ADSb out?

I do know that ACK makes a block 9 mod but the only difference in the 5 and 9 is the 9 has provisions for a GPS 232 altitude input if you have a device that can barometricaly correct GPS altitudes. I don't have anything that can do that.

Any ideas out there from you avionics experts.
 
I'm at my wits end trying to figure this out and need your collective help.

I'm running a Trig 31 transponder, ACK 30.5 encoder, Garmin 496 GPS, ( I know it's not 2020 compliant, but many others are running this and it works), Skyradar D2, and running WingX Pro. The only uncommon denominator between several working setups and mine is the ACK30.5 encoder. It's brand new and works as far as ATC can see.

All the settings have been verified with Trig and others that are using similar setups. The boxes are talking to each other.

The altitude on the face of the Trig and what ATC see's is correct. The ADS altitude that I put out is wrong and jumps around on WingX. All other indications are correct from other planes in the area.

My big question is where does the Trig get the altitude it sends out for ADS, and, how can it be sending out and indicating the correct altitude to ATC but the wrong ADSb out?

I do know that ACK makes a block 9 mod but the only difference in the 5 and 9 is the 9 has provisions for a GPS 232 altitude input if you have a device that can barometricaly correct GPS altitudes. I don't have anything that can do that.

Any ideas out there from you avionics experts.

I am researching what is needed for ADS-B compliance that will be required in 2020.

From the Trig web site:
"With a new software upgrade and a connection to an appropriate GPS, this will make the TT31 compliant with the FAA final rule on ADS-B Out for 2020."

So far, for me to be ADS-B 2020 compliant, I will need a new Mode-S transponder connected to a WASS TSO'ed GPS. (plus maybe a few other things)

It appears that you are not using a TSO'ed WASS GPS and you may not have the latest software update for the TT31.

I hope this info is worth more than you are paying for it. I just started two weeks ago trying to understand what I need to be 2020 compliant in the next 7-years and what is it going to cost me. I am thinking that I will do a complete panel redo with EFIS if I plan to still own the airplane and use it the way I use it today. If I no longer live in the LA Basin and do not need ADS-B to use the airspace that I use, I will be able to live without the ADS-B equipment as long as I stay below 10,000 MSL and below 2,500 AGL when above 10,500.

As I understand it, the TT31 should be putting out the correct ADS-B altitude with your setup but maybe because it is a the 496 GPS the WASS is turned off for faster updates. GPS altitude may have something to do with it. I do not have a 496 but understand that the W*** on a 496 can be turned on and off.
 
Thanks Gary.

I know that the 496 is not TSOd and compliant, but I also know that it will work with the Trig. It's putting out all the correct NMEA strings. Trig says it will work, but its not 2020 compliant. I have been in contact with others using it with a Trig.

My 496 is in WAAS mode. It in. FAST, 9600 NMEA out, TIS and VHF In. Fast mode limits the number of sentences and sends them out every 1second.

I'll call Trig again to see about an update. They did not mention that on our last conversation.
 
Trig only sends out baro altitude (that it gets from the encoder).. I suspect one of the pins on your grey code wires is bad...

Feed the Trig from GRT and see if you ever see that problem again :) (PS. you will have to disconnect grey code as Trig wants only one connected)

PS.. What is the reference to correcting GPS altitudes referring to?
 
Trig only sends out baro altitude (that it gets from the encoder).. I suspect one of the pins on your grey code wires is bad...

Feed the Trig from GRT and see if you ever see that problem again :) (PS. you will have to disconnect grey code as Trig wants only one connected)

PS.. What is the reference to correcting GPS altitudes referring to?

Thanks Rad.

Some units like the MX20 used to have a baro correction I think, but not sure. I get a good grey code test on the Trig but will check the wiring when I get back home in a few days. I don't have an internal GPS in the GRT so can't feed from it I don't think. Will have to check with GRT on that.
 
You do not need GPS for the GRT to act as encoder. Please note we're talking about providing baro altitude to the transponder via serial port -- it's more reliable of the two (fewer pins to go bad).

In either case, GPS alt adjustment you're thinking of is not applicable here.. We just need the altitude encoded for 29.92 (just like your ACK does now)... that's what Trig needs to send out to the ADSB world.
 
We considered Serial out from GRT but ...

You do not need GPS for the GRT to act as encoder. Please note we're talking about providing baro altitude to the transponder via serial port -- it's more reliable of the two (fewer pins to go bad).

In either case, GPS alt adjustment you're thinking of is not applicable here.. We just need the altitude encoded for 29.92 (just like your ACK does now)... that's what Trig needs to send out to the ADSB world.

Checking the gray code wiring is a good idea.
We had discussed that it was probably the (new) encoder) or the wiring from it.

To do the serial out from the GRT EFIS, the Approach Systems Fast Stack wiring hub that Widget is using would require ripping open their cable or ordering a new one. Trying to avoid that as he had a new encoder that "should" work.

I also have a "workaround" to suggest to Widget. (Inserting a short cable between the GRT and the Fast Stack cable and then tap into the serial out.) This would be temporary just to see IF that fixed everything.

James
 
Widget,
Bring plane to Mutha(aka Badger),along with a pair of dykes, after ACA. Establish Ebay account. Establish Stein account. Mutha will have you fixed up by mid January!:D
 
Widget,
Bring plane to Mutha(aka Badger),along with a pair of dykes, after ACA. Establish Ebay account. Establish Stein account. Mutha will have you fixed up by mid January!:D

I already have all those accounts..

Please see line below my signature.

Is Dykes a PC term?
 
Probably Normal

Don't go tearing everything apart just yet. What you are seeing sounds normal.

The altitude you see on the Trig is provided by the encoder and is referenced to 29.92 pressure. It will only agree with your altimeter if your altimeter is also set to 29.92.

The altitude displayed on the top of your WingX map is the GPS altitude provided by the built-in GPS rcvr in the SkyRadar box. It will hardly ever agree with your altimeter or the encoder. edit: Just to add, the WingX GPS altitude is not the ADS-B altitude sent to ATC and is only used within WingX for reference, terrain warning, etc.

When airborne, you will see yourself (yellow target) and the altitude reported by the encoder via the transponder just below the target. It should agree with the display on the Trig. Again, the altitude at the top of WingX is the GPS altitude of the SkyRadar box and will not agree with the Encoder.

Hope this helps.
 
Last edited:
Don't go tearing everything apart just yet. What you are seeing sounds normal.

The altitude you see on the Trig is provided by the encoder and is referenced to 29.92 pressure. It will only agree with your altimeter if your altimeter is also set to 29.92.

The altitude displayed on the top of your WingX map is the GPS altitude provided by the built-in GPS rcvr in the SkyRadar box. It will hardly ever agree with your altimeter or the encoder. edit: Just to add, the WingX GPS altitude is not the ADS-B altitude sent to ATC and is only used within WingX for reference, terrain warning, etc.

When airborne, you will see yourself (yellow target) and the altitude reported by the encoder via the transponder just below the target. It should agree with the display on the Trig. Again, the altitude at the top of WingX is the GPS altitude of the SkyRadar box and will not agree with the Encoder.

Hope this helps.

Thanks Mike,

I'm not talking about the GPS altitude on the wingx display. What I'm seeing that is incorrect is the ADSb altitude that is being displayed in WingX for my airplane. It shows my tail number above the plane displayed at my position but it displays my altitude incorrectly. All other traffic displayed is correct. I agree, it should agree with the Trig Display, but it doesn't.
 
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