Unfortunately, to me, those two paragraphs seem inconsistent. The first says SIL0 are disregarded. The second says they are forwarded.
Then another Q is what gets sent down the bluetooth link to say an Ipad running Garmin Pilot? No “uncertified” ADS-B out at all by the looks of it.
Is the GPS data (I mean the GPS position, from say a GTN unit to a TAS605) documented anywhere? The traffic data (e.g. the RS232 output from a TAS605) is I believe proprietary (and some of the various box builders have reverse engineered it).
Peter wrote:
“The simple answer is that any ADS-B received as SIL-0 will be ignored by our GTX series devices. As for a TAS/TCAS/TCAD and ADSB IN equipped aircraft (GTX 345 with GTS 800 etc) and an intruder with an SDA of 0 and a SIL of 0, the TAS target would still be forwarded as a TAS/TCAS/TCAD target.”Unfortunately, to me, those two paragraphs seem inconsistent. The first says SIL0 are disregarded. The second says they are forwarded.
I understand it as “the target will not be shown as an ADS-B target, but since the same airplane also has a mode A/C transponder, it will still be detected by the transponder based (mode A/C) TAS/TCAS/TCAD, and will be shown as a a TAS/TCAS/TCAD target”.
OK; so they are saying that the receipt of a SIL=0 radiation in conjunction with the receipt of Mode A/C radiation, will not make the target invisible. Only the A/C-based position will be presented.
Gosh, one must be grateful for small mercies 
It would have been outrageous if a transponder equipped aircraft became invisible to “TAS” equipped aircraft just because it is also radiating an uncertified ADS-B signal.
I wonder why the system is so strict. A €50 GPS from a camping shop is accurate to some tens of metres (usually much better) in 3D, especially if it does geoid correction which every “IFR” box (back to the KLN89) does do.
Peter wrote:
I wonder why the system is so strict. A €50 GPS from a camping shop is accurate to some tens of metres (usually much better) in 3D
‹shrug› My Garmin Aera 795 sometimes gives very insistent, and clearly false alarm by a real margin, ground and obstacle warnings for several minutes after it is turned on (which is also “close to after take-off”). Just waiting it out and/or connecting the external (suction-cup attached to the window/glareshield) antenna very suddenly solves the problem.
I’m not sure if that is because it has poor precision because of “not gotten the signal from enough satellites yet” or “not gotten updated ephemerides yet” or something like that.
wigglyamp wrote:
I received the answer back from Garmin about what can be displayed from the GTX345 and as suggested above, the GTX will disregard any SIL-0 targets.“The simple answer is that any ADS-B received as SIL-0 will be ignored by our GTX series devices. As for a TAS/TCAS/TCAD and ADSB IN equipped aircraft (GTX 345 with GTS 800 etc) and an intruder with an SDA of 0 and a SIL of 0, the TAS target would still be forwarded as a TAS/TCAS/TCAD target.”
I believe that the data for a SIL=0 target would still be pushed via the uncertified Blue Tooth interface and be presented on an iPad using Garmin Pilot or ForeFlight.
Peter wrote:
Is the GPS data (I mean the GPS position, from say a GTN unit to a TAS605) documented anywhere? The traffic data (e.g. the RS232 output from a TAS605) is I believe proprietary (and some of the various box builders have reverse engineered it).
The RS232 Garmin ADS-B Out==+ protocol is proprietary to Garmin. It has been reverse engineered as well as licensed by Garmin to some vendors. The ARINC 429 ARINC 743A protocol is public domain, but you have to pay to get the ARINC documents. I don’t think the Avidyne TAS interface is proprietary, or if it is they licence it.
The ARINC 743a describes the data needed in the interface for any position source, WAAS or not, to provide for the purposes of ADS-B Out. Most existing position sources simply don’t include the needed data in their protocol, for example Aviation data which is a common format used by GPS systems for moving maps or fuel totalizers does not include the needed information for an ADS-B Out position source.
Some of the protocols are pretty well secured – example of one bit of reverse engineering. IMHO that guy must have had “good info” from somewhere 
Lots of people have been up that road. But that example is the data stream from a GDL39, over bluetooth, to an Ipad, etc. Not related to this.
However, ARINC 743a – the data stream coming out of a WAAS GPS – ought to be available even though one has to purchase the document. But the TAS605 will accept this over RS232 so it can’t be quite the same data, can it?
ARINC 743a is a GNSS specification and not WAAS specific. AC 90-165A describes the requirements for a position source They do not need to be WAAS. A TSO C196 non WAAS GPS sensor will meet the requirements. Here is a list of the data labels used by the GDL90, an early UPS Apollo/Garmin ADS-B Out system uses if connected to an external GPS position source. Some of these values, but not all are transmitted by a KLN94 or other typical TSO C129a GPS.
The GDL 90 uses the following ARINC 743A labels for the transmitted ownship ADS-B state vector:
076 – GNSS Altitude (MSL)
103 – GNSS Track
110 & 120 – GNSS Latitude (coarse and fine)
111 & 121 – GNSS Longitude (coarse and fine)
112 – GNSS ground speed
140, 141 , 150, 260 – UTC time of day
130 – HPL
133 – VPL
136- VFOM
165 – Vertical GPS velocity
166 & 174 – NS and EW velocity
247-HFOM
273 – GNSS sensor status
370 – GNSS altitude (HAE)
Hmmm… and there is an RS232 version of this, too, because that is how a TAS605 -A is fed.
It is the information that is important, not the method of delivery, RS232 or ARINC or RS422 or internal interface.
