PilotAware
British Forum => Technical Support => Topic started by: jbone on January 02, 2021, 08:12:42 pm
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Hi, Can someone tell me please how to fix this ghosting of my own aircraft that appeared on a flight in November (I hadn't changed anything from before). It followed me right across the country and pretty much prevented me from noticing any other aircraft. I attach a couple of screenshots from Skydemon. The aircraft transponder is a non-ADSB Garmin GTX328 (mode S) and I have checked the HEX code on both that the PAW unit are correct. I can only presume the PAW is somehow receiving MLAT information with the aircraft ID missing?
I didn't think at the time to try turning off the transponder and a soggy runway has stopped me flying again since. I turned it all on again today in the hangar (as it happens with a PAW ground station just 50 meters away) and the ghost wasn't there, which is what makes think its MLAT. My PAW is a classic unit set up as a perminant installation with external antennae.
I want to sort it before I spend some serious dosh on an ADSB out solution,
Thanks, John
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Screenshot of the ghost...
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Hi John,
Your SkyDemon screenshot clearly shows a ‘known-position’ aircraft, though obviously not present in the location shown. Was it displayed in the same position throughout your flight, or did it’s position vary? Do you have any other screenshots?
From your Configure Screen you have both Mode-C/S (which would show Bearingless ‘Rings’) and Mode-S/3D (which would show uplinked Positional targets for ‘in range’ Mode-S equipped aircraft) disabled - so it can’t be a ‘Bearingless’ Mode C/S signal or anything to do with MLAT (that’s what uplinked Mode-S/3D is)!
The only things you can therefore receive (all of which would display as known position targets) are a directly received PilotAware or ADSB signal, or an uplinked FLARM signal from a Ground Station. I take it you didn’t have any other position transmitters deliberately or accidentally running in the aircraft (a SkyEcho for example)?
Looking at G-INFO, your Hex ID in your PAW certainly matches your Aircraft Reg, and you say you have checked your transponder settings (always worth rechecking though, just in case). If that’s definitely OK, and you definitely didn’t have another device running in the same aircraft, the issue has to be something to do with proximity between the PAW and Transponder 1090 MHz antennas or the PAW and transponder itself.
I see from G-INFO that it is an RV9 - Where in the aircraft are the PAW and transponder units mounted? How close together?
What type of antennas are you using for PilotAware (i.e. Standard Rosetta / Remote Internal or Remote External) and for the Transponder and where are they fitted? and...
How far apart are the PAW 1090 Rx and Transponder Antennas?
I would BTW also advise doing a software update as you are still running version 20190621 and we are now on version 20201101 - running old software certainly won’t improve the situation.
Regards
Peter
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Hi Peter, Thanks for your response. I'm afraid I didn't notice if the relative position of the ghost changed slightly during the flight, but it was "on top of me" the whole time. I probably should have fiddled with it some more at the time, but in an unplanned situation I tried to force myself not to get distracted by it too much.
I always get the 3Pi and ADBS-in antennae confused in my head, but if I've got it right, the 3Pi antenna is on the right underside of the fuselage, just aft of the main spar, and the transponder antenna is on the left underside, aft of the back wall of the baggage compartment (and they are 1.3 meters apart). The ADBS-in antenna is in the cockpit, on top of the turtle deck facing the sky and there is a flarm mouse right next to it. The setup has been like this for over two years with no problems. It's a classic PAW and it's mounted by my left knee, so next time I fly I should be able to pull out each USB in turn to see if that makes a difference.
Given your response that it's not MLAT, what is really confusing me is that I'm not getting the problem on the ground. I attach a screenshot taken this morning (the contact is my ground station). The HEX code in the transponder is definitely correct, I even took a photo so I could convince myself afterwards I wasn't going mad!
There were no other EC devices on board. I've been trying to decide between upgrading to a Garmin GTX 355 or just get a Skyecho, but I'm a bit nervous of compounding these sorts of problems if I go for the Skyecho.
Thanks again, John
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Ah,
Flarm mouse. That may be seen by the ATOM stations as a separate entity and transmitted back to your PilotAware? What ID do you have programmed into the mouse? IIRC it will need the same ICAO hex code at least.
Cheers
Ian
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Hi John,
I think Ian has spotted the issue, you must have a different ICAO code programmed to your flarm mouse.
thx
Lee
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I always get the 3Pi and ADBS-in antennae confused in my head, but if I've got it right, the 3Pi antenna is on the right underside of the fuselage, just aft of the main spar, and the transponder antenna is on the left underside, aft of the back wall of the baggage compartment (and they are 1.3 meters apart). The ADBS-in antenna is in the cockpit, on top of the turtle deck facing the sky and there is a flarm mouse right next to it. The setup has been like this for over two years with no problems. It's a classic PAW and it's mounted by my left knee, so next time I fly I should be able to pull out each USB in turn to see if that makes a difference.
I would agree, if it is a FlarmMouse running it’s default Flarm ID, that would certainly cause the problem - but (unless I am very much mistaken), the thing I am seeing in the second photo immediately to the right of the 1090 antenna on the turtle deck is a PAW Mouse GPS - NOT a FlarmMouse!
@John, can you please confirm whether you definitely have a FlarmMouse (but not showing in the photos).
Edit: Also, just to clarify - your ground station in your 3rd screenshot is still showing as an aircraft. If you update your PAW software to the latest version as I suggested earlier and also check that you have the latest version of SkyDemon, it will then show Ground Stations as Masts, which is much less confusing.
Best Regards
Peter
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Peter, Ian, Lee,
My understanding has always been that's the Flarm mouse in the photo. I certainly ordered one (in December 2017, Order number 1819)! The GPS receiver looks more like a USB stick. You can seem them both in this other photo, with the mouse on the left and the GSP receiver (which is painted black to stop it reflecting in the windscreen) on the right. I could have completely misunderstood however.
I just checked the instructions I used to set it up (20170721) and I don't see anything in there about programming the Flarm mouse with a Hex code. I've never been very clear on whether it was a Tx/Rx or Rx only. I certainly didn't set it up in any way, I just plugged it in.
If the consensus is its actually a GPS receiver, then I seem to have two. Otherwise, if it's a Flarm Mouse, can you please point me to the instructions on how to enter the HEX code?
If there is still uncertainty, I can always unplug it and see if I lose the GPS signal? The plane is hangared at home, so I can do that faily easily.
Thanks, John
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Hi John,
Could you upload your PilotAware .trk file to http://aircrew.co.uk/playback/ from the 4th of November and send me the link once uploaded?
James
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Not Like any FLARM Mouse I have seen before, and there is no FLARM antenna. It looks like the VK-162 G-Mouse USB GPS.
If that is the case then my theory gets thrown out of the window.
I certainly ordered one (in December 2017, Order number 1819)
from who? BTW is it connected to your PAW?
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I've been to the plane and disconnecting the 'mystery' mouse does NOT cause loss of GPS signal. It is stuck down and I'm reluctant to pull it off, so I cannot read what's on the underside. Disconnecting the small dongle that looks like a datastick does cause loss of GPS signal (and before I sprayed it black, it had the words "GPS/GLONASS" written on it - I know because I've got a spare)! However I also found a 2017 receipt from Pilotawarehardware for a "GPS Mouse on 195cm lead". So I am thoroughly confused now. Perhaps I got two GPS receivers, and when the kit arrived and I saw "GPS" written on the dongle and just assumed the other was the Flarm dongle I had wanted (and thought I had ordered). I cannot find a receipt for a Flarm dongle however, so perhaps I don't have one and I just confused the debate by mentioning it.
In which case we are back to the drawing board. All offerings welcome please?
Also (James), the track file for the problem flight (on the 4th November 2020) is missing from the list (on the screenshot). Maybe PAW just failed that day for some reason. (It does have a good Anker power supply, so that's not the reason.) I've just done a software update today, so maybe that will help in future.
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Yes it looks like you have two GPS. The GPS Mouse is an optional extra. One GPS will come with the PAW unit.
I would leave the GPS mouse fitted and remove the other one. Then you have more options to place it for best reception.
PilotAware does not sell FLARM products. That would be a bit like a Ford dealer selling Toyotas :-)
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Just noticed that your 3rd Jan Ghosting example is on the list available for download
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Hi John,
Thanks for the feedback.
The dongle you painted black is the standard GPS dongle which would have been supplied with your PilotAware Classic - fitted on a USB cable to extend it up onto the turtle deck so it has a good view of the sky.
The other one certainly isn’t a FlarmMouse (I have two of them). As Ian has said, it looks very like a VK-162 remote GPS Mouse as sold as an option by PilotAware Hardware.
When you say... ‘disconnecting the ‘mystery’ mouse does NOT cause loss of GPS signal’ - I am intrigued. I presume you mean you unplugged the other end of the cable that disappears into/behind the dash... but can you explain or describe what exactly you disconnected it from ?
Regards
Peter
p.s. Quick question for Lee - if both GPSs were plugged into the PAW at the same time, could that cause two slightly different positions to be fed to the Bridge?
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After looking at the track files from 3rd Jan, the other plane ground station. As you were running PilotAware version 20190621, SkyDemon displayed it as a plane. Latest versions of PilotAware and SkyDemon now show a ground station.
Why the plane was following you on the 4th Nov is a mystery. My guess would be it was also a ground station and some bug with using a 2019 PilotAware release with the latest SkyDemon was causing it to be displayed incorrectly. I believe after you update to the latest PilotAware you shouldn't have any issues.
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James/All,
[Edited after looking back through my testing notes]
We did have an incidence of something like that back in Jan/Feb 2018 (Version 20180129 - Ian C - RV7 out of Perth), where a Positional aircraft persisted on SD - following Ian’s aircraft in exactly the same position relative to his aircraft - for a considerable time after the other aircraft’s PilotAware signal had dropped out. It turned out to be due to a bug causing the aircraft’s last known relative position (from P3i) to persist because Ian’s PilotAware was still receiving an ongoing Mode-S signal from the same aircraft. But the bug was found and the problem resolved - so I’d be very surprised if it was the same sort of thing.
I'm still waiting for an answer from John about what he ‘disconnected his GPS Mouse’ from (to discount the fact that there still may be another device lurking in there somewhere) and if not, clarification from Lee about what happens if the two GPS sources were both plugged into the PAW at the same time (with presumably very slightly different GPS coordinates)?
Regards
Peter
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I have also seen a persistent 'ghost' aircraft follow at a relative position, but this was a number of updates ago and appears to have been fixed for some time.
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All, Thanks!
Peter, Sorry for disappearing (I've been distracted by something else since Monday). The original PAW GPS dongle (that looks like a datastick), is connected to the PAW by a USB extension. When I pull the extension out of the PAW, it loses position. Maybe if I booted it up with that disconnected, it would 'find' the one that looks like a mouse. I will try that when I put it back in the aircraft. I've also done the sortware update, so hopefully one of these changes will fix it. I confirm there is no other EC on board apart from the Garmin GTX328. It looks as if it's going to be a few months before the next flight, so the acid test will have to wait for a bit I'm afraid. I've just ordered a Skyecho, so I'll have some fun setting that up too.
Thanks for the help, John
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Hi John,
Thanks for the reply and OK on no other EC devices installed in your aircraft.
You stated previously that when you unplug the USB extender your unit loses its GPS position fix and in an earlier post that ‘disconnecting the ‘mystery’ mouse does NOT cause loss of GPS signal’.
With the PAW Classic, 3 of the 4 USB ports should normally be in use, with the small black WiFi dongle, the 1090MHz SDR (the larger black one with the thin antenna cable coming out of the end) and either the USB extender cable with your original ‘UBlox’ GPS plugged into the other end or the cable from the GPS Mouse (but not both). That means that the 4th USB port should be empty (unless the cable from the GPS Mouse has also been plugged into it in error - which is simply what I am trying to establish).
If not, I am at a loss to think what you ‘disconnected the ‘mystery’ mouse’ from? Clarification of this point may help us solve the mystery of your ghost.
Best Regards
Peter
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Hi Peter, Yes, both GPS antenna were connected at the same time (all 4 USB ports on the PAW were in use). This stems from me being confused and thinking the larger one was a Flarm antenna. I will remedy that before I fly again and hopefully that will be it sorted. Thanks to everyone for the help! John
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Hi John.
Thanks very much for that clarification. That makes the situation much clearer. No criticism from me as to connecting both units, I fully understand your confusion.
Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.
Once again, thank you for being so frank and open.
Best Regards
Peter
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Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.
This would not cause a ghost to appear
The issue is most likely a misconfiguration of ICAO code
I think we need to wait for John to provide the settings to determine this
Thx
Lee
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Lee, what do you need please?
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Hi John
apologies, I was going to ask for Screenshot of PAW Configuration screen, just gone back through thread and see you did post that previously.
In which case, simply a Track file of any flight where a ghost was seen should be sufficient
thx
Lee
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Hopefully Lee can now advise whether that is likely to have been responsible for your 'Ghost', though I'm not sure he will ever have tried that scenario - I know I certainly haven't , but I can do so locally to see what happens if required.
This would not cause a ghost to appear
The issue is most likely a misconfiguration of ICAO code
I think we need to wait for John to provide the settings to determine this
Thx
Lee
Hi Lee,
Like you, my first thoughts on reading this thread were that there must be two or more devices - one of which had the wrong Hex ID, but John reported having only his PAW Classic and Garmin GTX328 transponder and that both were running the correct Hex ID. This was borne out by subsequent screenshots and the fact that Mode-C/S and Mode-S/3D were both disabled seemed to rule out the transponder.
The mention of a FlarmMouse, however, raised the possibility of a second ‘positional’ device, especially as they are (as you know) habitually supplied coded with a non-ICAO ID, which would clearly cause this effect, though I was very sceptical as I could see no FlarmMouse, merely a Mouse GPS (as has since been confirmed). This leaves only the PAW Classic and John’s Garmin GTX328 transponder in the Aircraft.
As stated above, I had already discounted the transponder, as from John’s Configure Screen, he also clearly had both Mode-C/S and Mode-S/3D disabled in his PAW Classic, though in hindsight this of course also means that the transponder filter is (presumably) not selected.
Realisation of this made me reconsider the GTX328, but not being familiar with it I have googled it and managed to find and download copies of the Installation Manual and the Pilot’s Guide (from 2007, so not necessarily the most up-to-date versions, but the best I could find).
From these, it is obvious that the GTX328 is a sophisticated unit, with a very complex setup procedure. It is, however, reported as being incapable of broadcasting (or being converted to broadcast) Mode-S/ES (ADS-B) though it does transmit Mode-S acquisition squitter replies about once per second whether [external] interrogations are received or not.
It also appears to be the case that the GTX328 can be programmed to transmit both its ICAO Hex ID AND a separate ‘Flight-ID’ which - depending on the configuration at the time of installation, may be the normal Aircraft Reg OR a variable Flight-ID (e.g. for commercial use) ‘which may be the aircraft registration number or other call sign’ - configurable by the Pilot and changeable prior to each flight, though the manual states clearly that this can only be done if the unit is configured at installation by the installer to enable the user to alter the Flight-ID. The Pilot’s Guide makes no mention whatever of setting a Hex ID and this is covered solely by the Installation Manual.
Having read through the entire manual, it seems that depending on how the unit was configured at the time of installation, it would be possible to get to a situation where the unit was transmitting two different ID codes, though even if this were the case, surely it would only display as a Bearingless target and not a known position target - or am I way off the mark in that assumption?
I would certainly recommend that John updates his PAW as a matter of urgency to 20201101 and enables ‘Mode-C/S + Filter’ with realistic Range and Altitude Settings and ‘Mode-S/3D’
The plot thickens.
Best Regards
Peter
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Peter, Yes, that's right, the GTX 328 is a mode S, non-ABSD transponder (incapable of being upgraded to ADSB - don't get me going!). It is programmed with just the HEX code in (I uploaded a photo previously).
The question for me is "what has changed". I have flown, probably well over 100 hours with the PAW set up like this with no problem) then suddenly I get this problem. Since nothing in the aircraft has changed, I initially assumed it was something external. The answer might lie in the following:
Lee, there problem was the last time I flew the plane. There is no track file for the flight. There is a file for the previous flight and files from when I've been recently fiddling around with it on the ground, but nothing for the approx 90 minute flight where the ghost appears. Weird!
I'm not sure we are going to get much further. Why don't we wait and I'll report back when I next get to fly (although that could be a while)? thanks everyone, I'm very grateful for the help, John
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Hi again John,
Yes, I guess we’ll have to wait to do more flight testing. VERY frustrating for me too as we have lots of new stuff to test as reported elsewhere. Main priority however (having got this far) is to avoid catching the dreaded bug at this late stage until our turn for vaccination comes round!
One minor ‘gap’ in the evidence that has been rattling at the back of my head is the question of your USB Port Settings. They are presumably default, and may have no effect whatsoever, but the fact that they are not visible on the screenshot of your Configure Screen you posted earlier just makes me wonder. As your aircraft is ‘home-based’, could you please (at your convenience) take and post a screenshot showing the whole of the Configure Page with your current settings - to complete the evidence picture. I would appreciate it. No rush and Stay safe!
Best Regards
Peter
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Peter, I learned my lesson and kept the PAW unit here on my desk! Here is the screenshot. By the way, I have updated the software on a fresh SD card, but I put the old SD card back in for the purpose of taking this screenshot, so it would be on the old software (just to reduce the number of variable). thanks, John
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Just to close this thread off. Now I've been able to fly for a little while now, the 'ghost' aircraft has vanished. I've no idea why; it's just been one of those things. thanks to all who helped. John
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Hi John,
Thanks for the update. I’m still puzzled by the reasons for the problem as we have still never identified a definite cause. There are certainly no issues with the USB Port Settings. You say the new updated software/card appears to have resulted in your ghost ‘going away’, but I know of nothing in the update that would have caused that result.
Let’s just hope the ‘exorcism’ proves permanent, whatever the cause
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Experienced this today and it persisted until I restarted paw following which it was fine. At the time, i looked at the traffic page and the top entry was highlighted red though most fields on the row empty. Perhaps this is a clue? Sorry, no evidence- if it happens again I’ll try to remember to take screen shots. I have a classic with current os.
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Can I ask what version is being run, and do you have a track file?
Thx
Lee
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Running 20201101.
Never done anything with track files but point me in the right direction and i will check next time i go to airfield.
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Hi skyboy999,
To get the track files, power up your PAW and log on from your phone or tablet via 192.168.1.1.
The Track files can be found on the Tab at the extreme TOP RIGHT of the screen. They are listed by flight date / time. Individual tracks can be selected and then downloaded to your phone/tablet, or they can be downloaded to a memory stick.
Regards
Peter
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Thanks. I've emailed log file to support.
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I'm seeing a similar issue. Didn't know until we were flying along on FlyUK the other week and my flying buddies said they could see me twice.
I just told them to get a new pair of specs! :-)
Andy
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Hi Andy,
Trying to remember - are you running more than one EC device, and do they use separate GPS sources? I see this periodically on the likes of Glidertracker where the aircraft are for example running PAW +ADSB Out (or PAW +SkyEcho). Probably due to slightly different position reporting from the separate GPS sources in the transmitters.
Regards
Peter
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Yes.... very much suspect it is related to this.
I have PAW and ADS-B out. My ADSB out (Trig TT21) is fed by a separate Garmin GPS unit, not PAW. So yes they are totally independent.
I really should update the PAW GPS dongle, because the one I have looses its marbles sometimes.. It was even mis-reporting my altitude, once by approximately 4,000ft!
FWIW maybe if we have an ADSB out facility, we should be able to switch off PAW TX and only Receive PAW...... Thus relying on ADSB-out only if available. AFAIK PAW doesn't rely on packet acknowledgments, it just receives and decodes what it gets without providing an ACK.
Cheers
Andy
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Hi Andy
PAW does rely on acknowledgement for the GRID Uplink
This stops us filling the airwaves unnecessarily
We track your PAW position, and uplink information based upon where you are.
this is for Traffic and METAR
Regarding ghosting - so long as the ICAO is the same - this should not happen
I also sent an email Andy, did you see this ?
Thx
Lee
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Hi Andy
PAW does rely on acknowledgement for the GRID Uplink
This stops us filling the airwaves unnecessarily
We track your PAW position, and uplink information based upon where you are.
this is for Traffic and METAR
Regarding ghosting - so long as the ICAO is the same - this should not happen
I also sent an email Andy, did you see this ?
Thx
Lee
Ah fair enough, I'd forgotten about that GRDI uplink :-) Yes, have seen your email. I'll try to get the data.. I need to get it from my flying buddies really because I can't tell on my unit.
Cheers
Andy