PilotAware
British Forum => Technical Support => Topic started by: Mach2 on February 20, 2024, 12:19:30 pm
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I noticed that although Vector showed my PAW and Flarm transmissions, ADSB(out) through my transponder was blank. Ground testing showed the correct Octal code, registration and GPS data.
To check, I flew on 15 Feb with another aircraft that has ADSB(in and out) only and it could see me throughout. Have I made some wrong selection in Vector that could cause this?
John RV-8 G-RUVE 405F9B
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I don't think you're doing anything wrong because I can't see your ADSB on Vector either. I can see your PilotAware and Flarm.
Looking on FR24 I can see your two flights on 15 Feb but there is no indication whether the history is derived from ADSB, Mode S multi-lateration or Flarm (via OGN, as I understand it). In other words, there's no guarantee FR24 saw your ADSB.
What kit did the other aircraft have in it that only transmits and receives ADSB?
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ADSBexchange reports the flight on the 15th as being derived from ADS-B.
https://globe.adsbexchange.com/?icao=405f9b&lat=51.387&lon=-1.032&zoom=7.9&showTrace=2024-02-15×tamp=1708012250
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Thanks Both. The other aircraft was G-RVTX (40720B) with Skyecho and lots of Uavionix kit but only displaying adsb to the pilot. As mine has shown up as working I won't take the aircraft apart to fix it! Not sure about the lack of Vector data though. Thanks again for the help.
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Hi John,
Coming a bit late to this, but checking on Vector, your PAW and Flarm signals (as reported by the PAW ATOM-GRID Ground Station Network) are both perfectly acceptable, with coverage reports generated from 15th and 24th February and 3rd March.
Your ADSB, however, only indicates a report from a single date - 3rd March (reports are compiled from data from the past 30 days) and the signals are extremely weak - to the point of being only just visible by zooming in on my laptop screen. Taken with the positive PAW and Flarm reports for the same period, this would certainly lead me to deduce that there is a significant problem with ADSB-Out from your aircraft.
Looking then at the (secure) PilotAware Database, there are reports from multiple ground stations for both PAW and Flarm from your aircraft, but when checking for ADSB reports, there are reports from several of the same sites as reported your PAW and Flarm for 15th February and 3rd March, but (with the exception of Woodcote) only a minimum of 'data packets' received by any station and always at fairly short range. There are no ADSB reports whatsoever from your aircraft from 24th February.
Looking back further, reports indicate similar ADSB performance going back through 2023 - in fact I can only find what I would describe as 'acceptable' ADSB results from your aircraft from back in 2021.
In short, the results clearly indicate serious performance issues which require investigation.
As a start point, can you please advise as to what make/model of transponder you are using and what you are using to provide the GPS position data to it. A description of your antenna setup (i.e. antenna type and location (with photos if available) would also be helpful.
FYI, the other aircraft (G-RVTX) is showing typical SkyEcho results, with multiple data packets received on 12th and 15th February by our Sister Network (360Radar), but all at less than 10Km from the receiving site(s) and no reports whatever reported by any PAW ATOM sites since last October (which might just reflect that he was never close enough to any ATOM (Ground) sites for his SkyEcho transmissions to be received from the ground).
Sorry to be the bearer of bad news.
If you can give me the requested info, I will try to work out what might be going on.
Peter
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Hello Peter,
thanks for looking at this for me. I flew on 24 Feb and 3 and 15 Mar but none of those flights show on Vector. My RV-8 is based at RAF Benson.
I have Rosetta installed behind the panel fed by external ADSB(in) and PAW antennas on the foredeck next to the FLARM antenna for the PowerFLARM. PowerFLARM feeds the Rosetta which provides wifi position and traffic data to an ipad nav display with Skydemon.
I have a FUNKE TRT800H Mode S transponder with a standard TED antenna centrally mounted under the fuselage. It is fed with GPS by a TRIG TN72 Source. Approved for adsb SIL=1, I checked the transponder set up about a month ago and it was displaying a GPS feed with a correct location and SIL=1.
Any suggestions would be very welcome.
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How old is the Funke transponder? The new versions are not brilliant for ADSB Out, the old ones could be useless. Upgrading them requires a return to Germany and a fair number of Deutschmarks.
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Any suggestions would be very welcome.
I'm not that familiar with the Funke, but my first port of call would be to check the coax cable from the back of unit to the aerial.
If it's a BNC, then checking the the centre pin has not been pushed back in and is full inserted in the connector body, and the that both the inner and outer conductor buzz as continuous with a multimeter from one end to the other. Is the aerial grounded properly to the metal skin of the aircraft, if it needs a ground plane?
Either connector corroded? Quick squirt with contact cleaning spray?
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Hi again John,
Thank you for responding to my earlier post.
So we have established that your PilotAware/Flarm and Transponder/ADSB-Out installations are operating as two completely independent setups (similar to my own setup, though I use different hardware). This narrows down the possibilities to your Funke / TN72 installation or their associated wiring/antennae.
Looking at the secure PilotAware Database, I now see lots of additional PAW and FLARM reports from 405F9B from 13th March (from multiple ATOM sites) but no ADSB reports whatsoever from that date.
I have, however, now found a few random ADSB data packets received by the ATOM sites at Blackbushe, Kiddlington, (Abingdon), Thame (east of Oxford) and Woodcote from your flight on 3rd March, though all extremely intermittent and at varying ranges - only 2 or 4 data packets (which represents only a few seconds worth of transmissions) at any individual site.
The last ADSB report recorded on the database prior to 3rd March is one single data packet at 15Km from PWUKEdge (near Banbury) from 15th February, despite the fact that there are PAW and FLARM reports from multiple ATOM sites on that same date.
Prior to 15th February, there are multiple ADSB reports from flight(s) on 15th December 2023, from Ampney, Caldwell, EGBS, EGHP, EGLK, EGLM, EGTK, Kemble, Pidding, Radley, and including a single data packet received by PWUKEdge at 59Km and a few from PWThame (nr Oxford) at 8Km plus others from other local sites, all at varying ranges, so the ADSB was definitely transmitting at that time, though not necessarily reliably.
Points to check:
1. Anything that has changed since 15th December.
2. That you still have the correct Hex ID programmed in your transponder (unlikely to have
changed unless anyone has attempted to check and accidentally changed something, but if it is
incorrect, it ‘could’ still be transmitting, but won’t appear under 405F9B on the database - or on
Vector. (If you do find it has a different HexID, please let me know what this is and I will recheck
the database.
3. Your transponder antenna connections and cables as mentioned by the others above (this is IMO
the most likely cause of poor transmissions. Remember to check for ‘short’ as well as ‘open’
circuits. I have seen poor results caused by a build up of mud around the base of a TED antenna
resulting in loss of signal at that point).
4. That your wiring (and settings) are correct between your TN72 and transponder.
5. If none of those provide a solution, you need to check the transponder itself.
Please let us know how you get on.
Best Regards
Peter
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One for Peter really....
FlightRadar24 shows several flights for HEX 405F9B, including the 13 March. It is presumed to be ADSB, but FR24 doesn't say.
ADSBExchange shows the flights too, and reporting as ADSB data, this is from the 13 March -> https://globe.adsbexchange.com/?icao=405f9b&lat=51.738&lon=-1.261&zoom=9.5&showTrace=2024-03-13×tamp=1710334942
So it looks like the larger networks are picking up ADSB from an aircraft broadcasting HEX 405F9B.
Do they look like the correct flights?
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Hi Jeremy,
Thanks for that.
405F9B is certainly the correct HexID for Vans RV8 G-RUVE and the ADSBExchange link certainly seems to be reporting the flight as ADSB.
I need to look into this further, but have to go out this afternoon. I will take a look later when I get back.
Peter
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Hi again All,
Ok, so I have now had a chance to look at the FR24 and ADSBExchange Reports. I certainly can’t deny that they are both reporting G-RUVE’s flights on the dates in question.
Unfortunately, although ADSBExchange ‘seems’ to be reporting the flight as ADSB, we know that aircraft tracking sites (including FR24) use a combination of ADSB data from ground and satellite sources, plus MLAT from Mode-S as well as FLARM data (probably from the OGN Network - which also reports PilotAware), and data from goodness knows what other sources, when compiling their reports.
That’s the only realistic explanation I can think of for the virtually complete track reports from these sites, bearing in mind the paucity of ADSB data from G-RUVE on our database for 3rd March and the complete lack of ADSB data for 13th March. I’m pretty sure I could get a similar track report from just the PAW and FLARM data on our site, but unfortunately the PilotAware Playback tools are down at the moment (server maintenance apparently).
I will give it a try later and let you all know what I find.
In the meantime, I stand by my previous comments and suggestions to John for further investigation.
Best Regards
Peter
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However, for MLAT to work, the transponder and antenna must be operational, at least outputting Mode-S, which would be the same carrier as if it were also doing Extended Squitter from the GPS reference. So perhaps the GPS -> Transponder link isn't running, but surly the Transponder would indicate if the data is there or not?
Defiantly weird.
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Just to keep Peter on his toes, I'll also throw this into the mix...
I picked a different aircraft on ADSBExchange that was showing as MLAT (a PA28). I went back to find another flight, and it shows as MALT in the history. So I think the transponder is doing its job correctly....
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Just to keep Peter on his toes, I'll also throw this into the mix...
I picked a different aircraft on ADSBExchange that was showing as MLAT (a PA28). I went back to find another flight, and it shows as MALT in the history. So I think the transponder is doing its job correctly....
When you say ‘I went back to find another flight, and it shows as MLAT in the history’ do you mean another G-RUVE flight? If so, that would certainly confirm that the transponder was transmitting Mode-S at that time, but would also confirm that it wasn’t transmitting ADSB.
Unfortunately we had to stop recording Mode-S data as there was so much of it that the servers couldn’t cope, so I can’t verify that from the database.
However, for MLAT to work, the transponder and antenna must be operational, at least outputting Mode-S, which would be the same carrier as if it were also doing Extended Squitter from the GPS reference. So perhaps the GPS -> Transponder link isn't running, but surly the Transponder would indicate if the data is there or not?
Defiantly weird.
I fully agree, but there is no easy way to check that remotely. John did say he checked the transponder settings and GPS position a month ago, but he is using a Funke TRT800H, fed GPS data from a Trig TN72 and I’m not sure how that displays, or if (and how) it gives warnings if it loses the GPS feed. I know my Trig produces an ADSB Fail Alert on the control head, but it’s not particularly prominent.
I’ll keep on the case.
Peter
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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.
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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
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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
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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.
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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