adsb (out) not showing on Vector

[JCurtis]

I picked an aircraft at random (a PA28) that was live and showing MLAT. Then went back to look at previous flights for the same aircraft and they showed as MLAT too. Just to see what ADSBExchage recorded for historical flights.

So isn’t Mode-S shown as MLAT and with added ES becomes ADSB. If so it looks like things are working on the aircraft in question.

[exfirepro]

I picked an aircraft at random (a PA28) that was live and showing MLAT. Then went back to look at previous flights for the same aircraft and they showed as MLAT too. Just to see what ADSBExchage recorded for historical flights.

So isn’t Mode-S shown as MLAT and with added ES becomes ADSB. If so it looks like things are working on the aircraft in question.

Thanks for the clarification Jeremy.

You are of course correct, that Mode-S aircraft are reported as (and using) MLAT - otherwise, without their own ground radar, it would of course be impossible for the tracking sites to report the position and track of aircraft transmitting solely Mode-S signals.

You are also correct that Mode-S with ES is ‘accepted’ colloquially as ADSB and reported as such on tracking sites, even though the type of signal transmitted (known as DF17) is measurably different from ‘True ADS-B’. In practice FLARM and PilotAware are also forms of  ‘ADSB’ (Automatic Detection Surveillance (by) Broadcast (of position and other relevant information). They just operate on a different frequency to the normally accepted 1090 MHz used by ‘Traditional ADS-B’.

Together with cellular-based systems like SafeSky, PilotAware and FLARM are now referred to by EASA as part of the ‘ADSB-Light’ suite of surveillance tools being considered by EASA and the CAA as acceptable for use in ‘common usage airspace’ known as ‘U-Space’ - where it is anticipated that manned and unmanned aircraft will be allowed to operate together without the need for exclusion zones. This being the case, might the tracking sites not simply be using the generic term ADSB to describe reports derived from ‘known-position’ transmissions of any sort, possibly combined where available with positions derived by MLAT of ‘Pure Mode-S’?

I am not convinced that the label ‘ADSB’ on a tracking site, without further clarification and corroboration, provides incontrovertible proof that a Mode-S/ES installation is operating as intended. If that was the case, how do you account for the lack of specifically DF17 ADSB reports from the multiple sites on the ATOM-GRID Network which reported P3i and FLARM data from the G-RUVE, when the database also contains multiple DF17 reports from other aircraft in the same area during the same time periods?

Unless and until we can find another explanation, the logic clearly supports the likelihood of a problem with DF17 Mode-S/ES transmissions from G-RUVE rather than the reverse.

Regards

Peter

[Mach2]

To answer the last post, the FUNKE transponder was new 2 years ago - I had to exchange the old one which did not support adsb.  There is no warning of GPS failure in the transponder.  I can check the GPS data input using the setup mode but that is only available with the transponder in standby.  So I have checked it on the ground only.  I will check the cable continuity but it is a very simple single cable into the Trig and Funke plugs.

Flew yesterday and adsb exchange tags the flight as sourced from adsb data but nothing shown on vector.  After flight spoke to Pete Pengilly about the issue and he is going to put his test set on it next time he is at our base.

Thanks for all the help
John

[JCurtis]

I suspect you are transmitting ES just fine, regardless of what Vector is logging.
ADSBexchange will display MLAT or ADSB depending on what the feeders send.  I feed them ADSB and participate in MLAT too, same for FR24. 

If you flew nearer to Cambridge, and I knew when to keep and eye out, I could check my receiver in real-time to see precisely what is being transmitted.

[exfirepro]

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