PilotAware
British Forum => Technical Support => Topic started by: peteD on November 06, 2016, 04:06:48 pm
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Hi,I have mode S txpdr with ADSB out.
PAW is set to "Mode-CS (Beta)" with the correct Hex -ID.
I noted the other day intermittent an "red circle"(SD) warnings with no ID, at or near my level. Nothing seen(!) so presume this must be me. I know this is beta, just wondering if this is "normal" at present?
Thanks
Pete
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Hi Pete,
The filtering for ADSB and Mode S is done from your 'Hex Code' which you say you have entered correctly into 'PAW Configure'. You should also set your PAW 'Mode C/S Select' to 'Mode C/S + Filter (Beta)', otherwise it might still react to the Mode C (altitude) part of your Mode S transmissions. It is likely this is what has happened in your case. The other possible explanation, if you are near a major CAT airfield, is that the system might be reacting to the Mode C component of the transmission from a high power CAT Mode S or ADSB signal.
Hope this helps
Regards
Peter
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Hi, Thanks, I had used mode c/s beta because that is what the instruction manual(page 46) implied for a mode s txpdr.
So are you saying that because it's mode s + adsb, I need the additional filter? Will give it try!
Thanks
Pete
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Hi Pete,
Its because of the way PAW processes Mode C. If you are using the Mode C receive option with a Mode C or Mode S transponder you need to use the filter, in your case to ensure that the system doesn't inadvertently respond to the altitude transmissions from your Mode S.
I will have another look at the Operations Manual and if necessary have it amended.
Regards
Peter
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Hi All,
A Mode C or Mode S transponder will respond to a Mode C interrogation, so under these circumstances you need to select the 'filter' option on PilotAware, otherwise your own Mode C will be reported.
Thx
Lee
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Ok, thanks, I think the instruction manual (page 46)needs amending.
So out of interest, when is the mode c/s beta setting used?
Groundstation/no transponder?
Thanks
Pete
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Hi Pete,
Yes, you would use the Mode C/S (Beta) setting if you wish to detect Mode C and S transmissions, whether as a ground station or in the air, but don't yourself have a transponder. (ADSB out of course still has an active Mode S transponder, so you also need to use the filter).
The '(Beta)' reference by the way is just a reminder that the Mode 'C' detection software is still technically 'under development', but was released (early) because about 40% of all transponders in the UK are still reckoned to be Mode 'C' and consequently lots of our pilot users were asking for Mode 'C' detection. Unfortunately, compared to Mode 'S' transmissions which can be fairly easily identified from the 'Hex' code, Mode 'C' is a far more difficult beast to deal with, though from all reports the system seems to be working well, though we still need to do a bit more work on audio alerts from bearingless targets in general.
Regards
Peter
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I've got the filter on and I occasionally get Mode C alerts for my own aeroplane when I climb or descend.
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I've got the filter on and I occasionally get Mode C alerts for my own aeroplane when I climb or descend.
Hi Paul,
In the next release, something was added to handle this particular case, so be interested to see if you still see this issue after the next release
Thx
Lee
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Any Idea when the next release may be :)
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Any Idea when the next release may be :)
Hi Pete
Next release is imminent
Thx
Lee
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Pete
We will also change the instruction manual. Thanks for pointing this out. Feedback is always welcome
Keith
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...about 40% of all transponders in the UK are still reckoned to be Mode 'C'...
Sounds like a low estimate to me!
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...about 40% of all transponders in the UK are still reckoned to be Mode 'C'...
Sounds like a low estimate to me!
Hi Rob,
This was the best estimate we could find when we did our initial research. I would be happy to be corrected if you can point me to a more reliable source.
The point I was trying to make was that even if 'only 40%' of U.K. transponders are mode 'C', this clearly supports the development of PilotAware to detect such a major traffic group.
Regards
Peter
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Evening all,
I still receive many spurious airborne alerts that seem to come from my own mode c transponder & this undermines the value of other warnings.
Hex code is set on the config page although of course my mode C transmissions do not include any hex code.
Mode-CS+Filter(Beta) is also set.
I downloaded the tracks for post flight analysis but the post processor doesn't tell me anything about mode C traffic - it would be useful to reconstruct the traffic table from this file - can that be done?
To be frank, whilst most appreciative of all your efforts, I'm not interested in icing like the radar display until basic functionality works better. Spurious warnings are like crying wolf.
Any suggestions most welcome.
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I went flying today with the latest software and I didn't get a single spurious (own) warning. Has the algorithm been updated?
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I went flying today with the latest software and I didn't get a single spurious (own) warning. Has the algorithm been updated?
Yes it has !
Specifically enhancing the filtering
Would h interested in the software versions where users are seeing false positives
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I was running PilotAware Version(20161124) today & the suspect false warnings were bad enough to make me switch off.
Roger
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I was running PilotAware Version(20161124) today & the suspect false warnings were bad enough to make me switch off.
Roger
Hi Roger
Can you please send me
1. Screenshot of config page
2. Track file from flight
I will investigate
Thx
Lee
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Many thanks,
Sent by direct email due to 512KB attachment restriction.
Just before t/o a hercules flew close by at low level & we had a perfect mode c traffic alert/wng, then about 15 mins into the flight the ghost warnings began, no traffic seen despite repeated turning & scanning, then I turned the PAW off.
Best regards,
Roger
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Hi all.
The screen shot may be of interest.
Mode C seems to show the same return multiple times.
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Hi Eric,
That's normal. Think of the traffic screen as a sort of 'collection box'. The Mode C entries are all held here while the system analyses and compares them to establish whether they are threat aircraft or 'duplicate' altitude responses from mode S/ADSB aircraft already in the table, before deciding what to do with them. The T= bit denotes the time each mode C response has been in the system. They are only passed to the Nav System for display (with associated audio alert) if they are deemed to be a genuine mode C target and if this becomes the principle bearingless target at that point in time.
Roger,
I'm surprised you are getting false alerts. Mode C has proved pretty reliable with the exception mentioned by Paul above where rapid climb or descend could fool the system into seeing your own transponder as a threat, but Lee modified the software to deal with this and as Paul has reported, this problem seems to be now resolved. Your configure setup and log will give Lee the data to see what is going on.
Do please bear in mind that PilotAware 'Mode C' was released as a beta due to the number of users pressing for an early release. Although we are generally happy with it, it is still subject to ongoing testing and (where necessary), tweaking.
Regards
Peter
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I got a lot of alerts yesterday but that was because there was a lot of traffic around. :D
All the bearingless traffic I saw was Mode S though, giving a callsign. Don't think I saw any Mode C at all, though I concentrated more on the altitude than the registration.
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Thanks for the info.....now understand
the T bit..
Thanks EricC
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Sharing Rogers experience ....
There were no Mode-C Audio messages in the track file supplied, there were 2 sequences of Mode-S,
The two aircraft were :-
43C1AB, I saw it here (Apparently a hercules transport which you mentioned)
$PFLAA,1,4500,,125,1,43C1AB!RRR298,,,,1.3,8*63
$PFLAA,2,3000,,125,1,43C1AB!RRR298,,,,0.0,8*60
This is saying it was within 125ft of you vertically - that's pretty close!
400FB6 (G-JKMH)
$PFLAA,3,1500,,200,1,400FB6!GJKMH,,,,1.5,8*34
This is saying it was within 200ft of you vertically
There were a total of approx 30 Audio messages, this issue was that the signal was coming and going causing the
threat to appear to reduce, then increase.
Definitely not a Ghost
Maybe you know G-JKMH ?
Thx
Lee
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Well I certainly stand corrected on this one.
Having checked the registration on FR24, we were in the same part of the sky at the same time yesterday & a big lesson learned.
Thanks everyone for their comments & apologies for my criticism of the product.
Best regards,
Roger
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Having checked the registration on FR24, we were in the same part of the sky at the same time yesterday & a big lesson learned.
We are all still learning Roger ;)
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Hi Roger,
Good to get positive feedback from Lee and to know the system was doing what it is supposed to. I'm not sure what 'Mode C/S Detection Range' setting you are using, but I take it you know this is in effect a 'sensitivity control'. If you get too many 'Bearingless' target messages ( - i.e. the Traffic Notice / Traffic Alert / Traffic Danger variety), it might be worth trying a shorter range setting, which will decrease the warning distance but significantly reduce the number of alerts. ''Short' or 'Medium' Range settings generally work well unless you operate very close to a large airport or very busy airfield,when you may want to try Ultra-Short Range, but tread carefully!!
Any problems get back in touch.
Regards
Peter
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I am continuing to get spurious returns, I believe, on the latest version.
I am using the '+Filter' option, and have '+-2000'' and 'Short Range' set. Descending from FL100 over mid-Wales today I was getting an intermittent warning of Mode C traffic either 100' or 200' below me most of the way down.
Unfortunately I didn't save the settings page nor track logs.
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Hi Graham,
You say you are running the latest software version, which includes a fix for an issue where own transponder could register as a threat during rapid climb or descent? This sounds very like the problem you were experiencing, but should now be fixed.
Lee has been away, but back this coming week. If you have your track file, I'm sure he would be keen to take a look at it.
Regards
Peter
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I am continuing to get spurious returns, I believe, on the latest version.
I am using the '+Filter' option, and have '+-2000'' and 'Short Range' set. Descending from FL100 over mid-Wales today I was getting an intermittent warning of Mode C traffic either 100' or 200' below me most of the way down.
Unfortunately I didn't save the settings page nor track logs.
Hi Graham
You say warnings below ar 100-200 Ft.
This seems strange, if the filter was not working, and you were descending, I would expect your own transponder to appear above, not below you.
Are you able to compare the reported barometric altitude of PilotAware versus your transponder.
Also a look at the tracks would help
Thx
Lee
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Hi Lee, the PAW box is in the aircraft 7 miles away now, and I won't be going there for another two weeks as I'm off to the US on business tomorrow morning! I do remember noticing on the ground that the PAW QNH was 1032 - exactly that as given by both Sleap and Welshpool over the RT.
Next time I fly, if I see the same symptoms I'll take some screen shots. Remind me again how I save the Track Logs?
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Track logs are saved automatically, and can be downloaded from the logs page in PAW. If PAW is fixed in the aircraft, and you have the latest software, then you can sync it to a pen drive for viewing back home.
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Email with some logs sent to Lee. I managed to sneak to the airfield and download them. :)
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Well done Graham. The track logs will certainly help Lee get to the bottom of things.
Regards
Peter
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Hi Graham,
I have taken a look at the logs.
I agree I think this is seeing your own transponder - that is strange, and does look like an issue
we had seen on an older release.
Can you firstly confirm which release you are using ?
Also what your Mode-CS selection settings are ?
I guess this could be a while, as you mentioned you were out of the country on business
Thx
Lee
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Hi Lee, I snapped this on the iPad when I downloaded the logs. It's not from the date of the flight, but nothing changed in the set up since.
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Thanks Graham, OK, I think I see what is happening here ::)
The current algorithm tries to 'learn' that this is your transponder using a set of heuristics about power, and relative height.
The data you collected is very good, I think I can use this to try to refine the algorithm.
I also need to add more logging, because it would appear that your transponder signal (received by PilotAware) is below the threshold
defined as identifying your own transponder.
In order to diagnose this I need additional logging
Thx
Lee
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Hi Lee,
When I get back from the US I'll collect and send you some more.
Perhaps the low signal level is due to relative positioning of the PAW (coaming) and the transponder antenna (further back under belly of aircraft). When I gather some more track data, I'll move the PAW to a different location, perhaps by the rear pax side window.
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On the ground and just playing - with it set to mode c/s (But NOT the filter option) would I expect to always see a return from my own mode C transponder? Because I'm not seeing mine at all, never seen it in fact.
Also, daft question - if you want to use the option of seeing mode c/s traffic, why would you ever select the option not to use the filter? Surely if you do have your own mode c or s transponder then that's what you want - or if you don't have your own mode c or s transponder then it wouldn't make any difference to you whether the filter is selected on or not...??
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Hi Jonathan.
On the ground and just playing - with it set to mode c/s (But NOT the filter option) would I expect to always see a return from my own mode C transponder? Because I'm not seeing mine at all, never seen it in fact.
Yes you should see your own, try taking a look at the traffic page to see if it is listed.
Also, remember it will only be seen when it is interrogated, so may not being interrogated
Also, daft question - if you want to use the option of seeing mode c/s traffic, why would you ever select the option not to use the filter? Surely if you do have your own mode c or s transponder then that's what you want - or if you don't have your own mode c or s transponder then it wouldn't make any difference to you whether the filter is selected on or not...??
No this does make a difference, so if you have no transponder - do not select the filter.
Thx
Lee
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Hi Lee
I'm also seeing myself with Mode S/C either 100ft above or below. I'm using your latest version that you have updated for RB Pi2 v1.2. Hopefully you will have a fix shortly, this is the first flight since upgrading my hardware.
Just for info I have a Trig TT21 Transponder with ADSB out with is getting my GPS from my MGL Explorer lite
Allan
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Hi Lee
I'm also seeing myself with Mode S/C either 100ft above or below. I'm using your latest version that you have updated for RB Pi2 v1.2. Hopefully you will have a fix shortly, this is the first flight since upgrading my hardware.
Just for info I have a Trig TT21 Transponder with ADSB out with is getting my GPS from my MGL Explorer lite
Allan
Hi Allan
You say mode s/c. Do you mean both ?
Mode C - possibly, mode S are you sure ?
Can you supply the track of your flight where this issue occured
Thx
Lee
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I flew yesterday and I was getting quite a few alerts on myself...mostly 100ft out, but at one point I got it 200ft out. I have a Mode C transponder.
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I flew yesterday and I was getting quite a few alerts on myself...mostly 100ft out, but at one point I got it 200ft out. I have a Mode C transponder.
Hi Paul,
Was this during a climb / descent ?
Also, can you please provide he track file so I can investigate.
thx
Lee
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Sorry but i can't find the switch for activating the c/s beta, please see attached photos, unit should be a pi 2b
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Sorry but i can't find the switch for activating the c/s beta, please see attached photos, unit should be a pi 2b
Can you please show a screenshot of the home Page ?
Thx
Lee
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That was fast
Pls see attached
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That was fast
Pls see attached
Hi Peter,
Looking at the home screen it appears that either you do not have a PilotAware bridge fitted, or the Bridge has a fault.
the line here :-
TRX .... Unavailable TX=0 RX=0 ...
Hence there is no valid barometric pressure reading available for altitude comparison.
Thx
Lee
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Aha, that is correct, does the bridge need to be in place to monitor mode c/s , or does the presserende just need to be corrected ?
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Aha, that is correct, does the bridge need to be in place to monitor mode c/s , or does the presserende just need to be corrected ?
Initially we allowed the user to dial-in a pressure setting, but users kept forgettin making the relative altitudes incorrect.
We took the decision to only allow the automatic calculation with an on-board pressure sensor
Thx
Lee
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Mode C - possibly, mode S are you sure ?
Sorry Lee, it was mode C, when I get time I'll send you my flight logs.
Allan :D
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Hi Lee
Thanks, can the mode c/s be activated by installing a USB pressure sensor ?, and if yes can you suggest a model?
Thanks for your very prompt answers, impressing !
All the Best from D
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If the baro sensor on the Bridge is addressed the same as before the Bridge came along, I might have a small board around you could plug onto the Pi instead of a bridge to get the Baro working. Depends what Lee and his team have done with the development of the Bridge.
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That is very kind !!!, lets see what lee comes up with :-)
brg
Peter
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Mode C - possibly, mode S are you sure ?
Sorry Lee, it was mode C, when I get time I'll send you my flight logs.
Allan :D
Great data, have sent email, I think I can see an issue on the first interrogation of your Mode-C transponder
Thx
Lee
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If the baro sensor on the Bridge is addressed the same as before the Bridge came along, I might have a small board around you could plug onto the Pi instead of a bridge to get the Baro working. Depends what Lee and his team have done with the development of the Bridge.
Hi Jeremy, Peter,
Unfortunately not, at startup the software does a complete selfcheck of all of the systems including Baro and Transceiver - any detected failures (reported with a red icon on the home page) and it will not run I'm afraid
Thx
Lee
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Hi Lee
Thanks for your answer,
this of cause is one way of selling the bridge, but unemployed at the moment i unfortunately have to be picky what i spend my money on, and the bridge = 1 hour of actual flying time.
for testing purposes is it possible to go back to a previous software version where mode c/s is visible ?
by the way, how may pilot aware units are sold to denmark ?
pleased to hear
best regards
Peter
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I think I managed to outwit the ModeC/S + filter last night. I was night flying in VMC on top of an overcast layer, and I am sure there was not a soul about, futher East Midlands Radar were giving me a traffic service and they were quiet, and nothing seen.
I started a descent from 3500 to 3000, at around 500fpm, and within a few seconds got a ModeC alert, red ring @ -100ft. I swiftly hit the altitude hold and as quickly as it appeared it then disappeared. I had a good look out and was so convinced it was my own ModeC transmission I continued descent. On doing so the same thing happened but within around 2 seconds the warning vanished again.
What I think is happening is that the cabin pressure is lagging a few hPa behind the actual barometric pressure as the autopilot starts the descent, then equalises again. So the transponder is reporting a slightly higher pressure.
I found I can sometimes get the same short spurious -100 below by opening my DV window!!
Not sure if this helps in development. On the whole though, the filter is very helpful.
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Hi Doc
I think I managed to outwit the ModeC/S + filter last night. I was night flying in VMC on top of an overcast layer, and I am sure there was not a soul about, futher East Midlands Radar were giving me a traffic service and they were quiet, and nothing seen.
I started a descent from 3500 to 3000, at around 500fpm, and within a few seconds got a ModeC alert, red ring @ -100ft. I swiftly hit the altitude hold and as quickly as it appeared it then disappeared. I had a good look out and was so convinced it was my own ModeC transmission I continued descent. On doing so the same thing happened but within around 2 seconds the warning vanished again.
What I think is happening is that the cabin pressure is lagging a few hPa behind the actual barometric pressure as the autopilot starts the descent, then equalises again. So the transponder is reporting a slightly higher pressure.
I found I can sometimes get the same short spurious -100 below by opening my DV window!!
Not sure if this helps in development. On the whole though, the filter is very helpful.
I think you are right - you have outwitted my filter >:(
I have had a few reports about rapid ascent/descent, but opening the window is a new one, but I can see what is happening.
The Filter is using a number of heuristics to remove YOU (ie, Mode-C you) from its list of threats.
I have identified that there is a 10 second window, and if you ascend descend quickly enough it no longer thinks that your own Mode-C transponder is you - basically it moves outside the filter window.
So at 500fpm, that is 83ft over 10 seconds, add on the coarse granularity of 100ft altitude encoding for Mode-C and there you have it!
I had not thought about the window opening, but of course, this could have the same effect of altering the internal pressure, and fooling the pressure sensor temporarily, but that is something I cannot address.
Its at this point where I put on my jobs-worth hat and say - hey the Mode-C is BETA ;)
We think we have a fix for this particular situation of rapid ascent/descent, which we hope to test out in the air as soon as the weather improves, and if this provides better behavior under these circumstances, it will become part of the release.
Thanks for the feedback Doc- this is useful information
Thx
Lee
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Would this still happen if Doc has ADSB transmissions?
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Would this still happen if Doc has ADSB transmissions?
I am afraid so, Mode-A, Mode-C, Mode-S/ES are independant of each other.
When the transponder responds to a Mode-C interrogation, it simply sends a 24 bit response which is interpreted
as 4 octal values between 0000 and 7777
There is no way to correlate this information with ANYTHING else the transponder has produced.
All 1090Mhz transmissions were invented in the dark ages, using a modulation technique (Pulse Position Modulation) that is never used in any modern system. When the US introduced UAT on 978Mhz which runs complementary to 1090 transponders, they chose to use FSK (Frequency Shift Keying) as a superior modulation technology.
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Your beta is virtually perfect though Lee. I can't say I have seen the opposite happening on climbs, and it is only a short lived blip on descent commencing. And as you say....its a beta!! ;)
I am quite content to keep my DV window shut as I do 99.9% of the time! I only opened it to test my theory, and also learn how it affects my pressure instruments if operating on the alternate air feed i.e cabin pressure)
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Your beta is virtually perfect though Lee. I can't say I have seen the opposite happening on climbs, and it is only a short lived blip on descent commencing. And as you say....its a beta!! ;)
You don't have a high enough performing aeroplane! ;)
I think my spurious alerts were when I was in the climb. Good performance with this cold air at the moment. Sometimes 200ft out! ;D Oh yeah, I was going to e-mail the files, wasn't I...
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lol! She still climbs at around 2000ft per minute in a Vy climb up to 3-4000' and may be higher in this cold weather we have- not bad for a 1956 model!! Like you say though, I fly her gently, so cruise climbs or if under IFR 500ft per minute only!