OK; but the GPS has to be a WAAS box. So for me, KLN94, this would not work. I could get ADS-B OUT with a GTX345 which would be doing it in isolation from everything else, using its own internal WAAS GPS, and otherwise acting as a standalone GTX330 does.
It is possible that a KLN94 could feed a GTX330 ES and I would then be radiating ADS-B OUT with SIL=0 so only uncertified traffic detectors would see it, but I very much doubt the GTX330 ES would take in KLN94 GPS data. The GTX330 cannot even use the KLN94 ground speed for ground/air mode switching, even though this is shown in the GTX330 manual… some indications exist that this bug was quietly fixed recently, under the “KLN89” heading.
Incidentally I have not managed to establish that a GTX345 will feed traffic data to anything I have. So it’s traffic merging feature (TAS605 + ADS-B IN) is probably useless. Of more concern in the future is that it may be that the Sandel EHSIs cannot display any traffic data other than what is coming directly from a TAS6xx or similar active TAS box.
It’s funny to observe that until I actually want LPV, my best course is to do exactly nothing 
Peter wrote:
The GTX330 cannot even use the KLN94 ground speed for ground/air mode switching, even though this is shown in the GTX330 manual… some indications exist that this bug was quietly fixed recently, under the “KLN89” heading.
Using GS to switch between ground/air mode doesn’t seem reliable with our slow-speed aircraft. It must not switch to ground mode in the air even if you are flying near Vs0 in a strong headwind, while not switching to air mode during taxi.
The Trig TT31 we use in two aircraft needs both a GPS and an ADC to do the switching without the use of a squat switch (or separate pressure sensor).
My GTX330 indeed uses a differential (pitot-static) pressure switch; this also drives the TAS605. That was after I paid £500 to an avionics shop to make that ground speed connection Predictably both Avidyne and Garmin washed their hands of it – just like they did on the GTX330 → TAS605 ARINC429 pressure altitude connection which also doesn’t work (although there is a post here somewhere stating that after some firmware upgrade this now works).
The Q of whether to radiate uncertified ADS-B, on the grounds that it is better than nothing, is really here and how many people who you are likely to hit use one of these. Personally I don’t know a single such pilot.
If anyone has managed to get anything out of a KLN94-GTX330ES connection, I would be interested.
