Hi John / Jeremy,
As I have said earlier, there is definitely something very strange going on here.
I had a long chat to Chris, our network and data expert on Friday and neither of us can understand exactly what is going on. If these were short local flights, it would be possible for your transmissions not to be picked up by individual ATOM sites - as they are almost certainly less densely located than FR24's sites, so you could simply have been 'out of range' or obscured by topography or antenna positions. But you have been flying extended flights across large areas of the country highly populated by networked ATOM sites, all of which are reporting ADSB traffic - except it seems from your aircraft. It just doesn't make any sense.
It wouldn't be the first time, BTW, that I have come across a professionally wired ADSB-Out setup that had the correct wires on the wrong pins, or even the wrong wires on the right pins, or had developed a defect in the antenna feed - or even lost the antenna off the bottom of the aircraft since it was fitted, so
always worth double-checking everything. Another example I came across recently (not a certified installation) even had a wrong frequency antenna installed. Another example I have come across several times is where a build up of mud on the antennas (especially if wet) has significantly reduced the transmitted signal - a not unlikely occurrence with the weather we have been having recently. Any of these latter options could result in a weak transmission signal, which 'might' still be picked up by densely located 'FR24 type' sites - and the reporting software would then 'fill in the gaps' in the reported track, but would not necessarily be reliably visible to our more sparsely distributed network (Remember aircraft tracking is NOT our primary purpose).
I had already noted your flight on 21st. Unfortunately, our network servers were down that day as what was planned as an overnight server upgrade on the Wednesday night had gone wrong and Chris spent all the following day recovering the issue and completing the migration to the new servers. It didn't affect the operation of the individual ground stations, but no data is available for 21st March. If you can let me know in advance when you will be flying next, however, Chris has agreed to set up the system to look in depth for your aircraft and we can also compare any data found with what is seen across other sites including 360Radar and FR24 at the same time. I know you already have my email and, I will PM you my phone details as well.
You might also be interested in a couple of articles by Adrian, CFI at 'Get Your Wings' Flying School, on installing and setting up a range of transponders (including the TRT800H) for Mode-S/ES ADSB-Out using an uncertified GPS source and also testing to determine that the finished product is supplying ADSB Out at the correct Sil level. The only real difference with your installation is that you are using the TN72 to supply 'certified' GPS data, but the principles are the same and the test software is
very useful if you don't have any other reliable test set available locally. All it needs is a Windows laptop, an RTLSDR and a small 'twig' antenna, plus the software which is downloadable from the site below. I use it regularly to check the validity of ADSB-Out installations for BMAA and LAA MODs, so I know it works.
https://getyourwings.co.uk/connecting-an-uncertified-gps-to-a-transponder-for-ads-b-out/https://getyourwings.co.uk/uncertified-gps-testing-or-just-checking-the-output-from-your-transponder/Like Jeremy, I would be happy to carry out the tests for you if we weren't so far apart, but I'm up in Scotland. Happy to send you an SDR and twig antenna F.O.C. to run the Get Your Wings software so we can try to resolve this matter once and for all, if you email me your address.
Best Regards
Peter
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