PilotAware
British Forum => Technical Support => Topic started by: buzz53 on July 30, 2020, 09:08:53 pm
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Short question: up to what range should I expect to receive OGN-R uplink data?
Long version: Since I am based in rural East Anglia it can be rare to see enough PAW airborne traffic to make useful assessments, so in the past I have tried to use ground stations as a more repeatable test. I think this is probably more important anyway as the uplink is becoming the unique advantage of PAW.
Having had disappointing results last summer with internal antennas in my RV6, I decided it was time to drill a hole in my bottom and fit a proper one. My results today were a bit contradictory. In the hangar, I had intermittent contact out to 27km on a PAW target which was encouraging and gave confidence in my home-made antenna.
However, on the test flight, I didn’t seem to pick up the UKWRM OGN-R station beyond about 2 nm, which is pretty much what I found last year with the internal antenna, and clearly not a lot of use. This is based on: the appearance of the OGN-R label on the RADAR screen; the appearance of the UKWRM ground station icon on the RADAR screen; and on the reporting of MLAT traffic on the radar and in the track file (I think).
Is this a valid test? How are those indicators controlled? I believe the ground stations transmit a beacon every 15 seconds or so regardless of the detection of any nearby PAW aircraft. Is that correct and if so, is that used to drive the OGN-R flag, station ICON etc?
What else would give rise to this contradictory performance? Is it possible UKWRM is just broken? Last year I had similar results from UKTIB so I suspect not.
BTW looking at the datasheet for the PAW radio module, my calculations suggest free space range should be about 150km which seems an awful lot more than is seen in practice even air to air. Am I missing something?
Alan
PS no voltage or throttling issues!
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Hi Alan,
Short question, but unfortunately no short answer as there are so many variables involved.
Transmission and reception at these frequencies is theoretically ‘line of sight’, which would imply ‘to the horizon or beyond - especially at altitude’.
In practice, however, transmission/reception range is generally restricted - predominantly by topographical features (though not many hills in East Anglia) or more significantly by physical obscuration by aircraft metal or carbon fibre bodywork, engine(s), human bodies, fuel in tanks etc., between aircraft or between aircraft and Ground Station antennas. The type and position of antennas on each aircraft, whether they are fitted internally or externally and if appropriate on a suitable ground plane, plus the length and type of coax between the antennas and receivers or transceivers can also have a significant effect on transmission/reception range.
Rebroadcast is of course subject not only to the vagaries of installation in individual aircraft, but is also dependent on your aircraft and the target aircraft both being in range of at least one Ground Station at the same time, which in an area like East Anglia, (or in my case Scotland) where Ground Stations are widely spaced and not particularly numerous, is not always possible. Despite optimum siting and use of relatively high gain antennas (where permissible), geographical (and in particular topographical) location of Ground Stations can have a significant effect on rebroadcast range, particularly in certain directions.
Having said all that, if you give me your home airfield and aircraft registration / Hex ID, I can take a look on the Network Database to see from which Ground Stations and at what ranges it has been reported.
Looking forward to hearing from you.
Best Regards
Peter
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What else would give rise to this contradictory performance? Is it possible UKWRM is just broken? Last year I had similar results from UKTIB so I suspect not.
You can go onto https://www.gliderradar.com/ (https://www.gliderradar.com/) and see the status of a ground station, and see coverage...
However, this is just "belt and braces" as it is not a map of received P3i in aircraft, it's a map of aircraft received...
Some coverage maps below, depends on who made the antennas, I'm guessing, and therefore gain...
Have you any way of testing antenna performance? Are you 100% happy with cable terminations?
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Just to add a high performing ATOM-GRID station on the North Downs... topography allows excellent coverage to the South, but not to the North...
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Hi Steve,
Thanks for the screenshots. I agree GliderRadar’s coverage maps can be a useful tool to show general coverage area, but as you say they display coverage for ‘aircraft’ and have limited scope for configuring them to obtain information on specific transmission types.
I find the OGNRange tools more useful in this respect, as you can tune them to display coverage range for a specific OGN or PAW receiver for a specific time period e.g. ‘Today’, ‘Yesterday’, ‘Last 7 Days’ etc. Looking at https://ognrange.glidernet.org for both UKWRM (FLARM) and PWUKWRM (P3i) for ‘yesterday’ and ‘last 7 days’ for example, clearly shows that the station was operating on both protocols over that period (though wouldn’t of course show any short term outages).
Unfortunately I don’t have direct access to PWUKWRM (Colchester) via the PilotAware Network at present, but if Alan gives me his Hex ID or Reg, I can do a search for him from one of my own sites using the ‘My Aircraft’ Tool, which will show all PAW ATOM Ground Stations on which his aircraft has appeared, with maximum ranges for each Mode - ADSB, PAW and FLARM. Just one of the benefits of an efficient professionally created secure network.
p.s. Alan, if you don’t want to ‘publicise’ your details, send your Hex/Reg to me by PM and I’ll reply similarly and only report the basic outcome on here.
Best Regards
Peter
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Thank you Peter and Steve.
The HexID is F4406A, flight yesterday from Elmsett EGST about 16:50.
I appreciate there are many variables but I think it’s safe to say it should be better than 2nm? I imagine my setup is fairly ideal, being an external monopole on the bottom of a metal aircraft. Currently for convenience using 2m of RG174 so would expect a small reduction in performance but not the drastic result I am seeing.
I’m quite confident about the antenna as I have a VNA for tuning and which I use for other 868MHz activities. Although on a slight tangent, I did measure both the official PAW and ADSB antennas on another RV6 for comparison and found them both surprisingly over-long. The ADSB was 71.5mm compared to a standard transponder antenna at 56mm (measured from where they emerge from the metal base). I would have expected them to be the same. The PAW was 86mm which is the ideal freespace length but I would have expected less in an actual antenna.
Thank you for the pointer to the gliderradar site. I mentioned UKWRM in error yesterday, it should be PWUKWRM of course. It’s clear from the coverage maps that that PWUKWRM is a relatively poor performer compared to PWUKTIB. It’s also poor compared to UKWRM which seems odd given the much higher airborne power of PAW but perhaps this is due to the SDR receiver for UKTIB performing better than the PAW hardware receiver.
Back to the main subject, these maps are as you say air to ground and I wondered to what extent they reflect the performance in practice in the other direction? I assume the PAW base station power output is adjusted compared to a normal aircraft PAW to give the same max legal 500mW ERP allowing for the base station antenna gain? In which case, as the aircraft doesn’t have the benefit of a gain antenna, I assume the uplink performance is inevitably going to be significantly worse?
I will try to borrow another PAW for my next flight but with 30 degrees forecast today I think that will need to wait!
Alan
PS just seen Peter's later mention of OGNRange, I thought that had packed up but will take another look.
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RG174 will give 2db of loss at that frequency
That is a lot of loss
Thx
Lee
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Hi Alan,
There are several OGNRange sites, some of which seem to have come and gone recently. I find the one I posted the link to above, the most reliable these days.
OK - I have done a search and only 2 records show up for F4406A * both from 30th July:
PWHempstd reporting only 4 ‘pings’ at between 20 and 30Km (with a max of 27Km) - so a bit of a ‘fluke’, and
PWUKWRM (Colchester) reporting 248 ‘pings’ at <10Km and 12 ‘pings’ at between 10 and 20Km (with a max of 12Km).
By comparison, my own most recent flight from 24th July - with a PAW 1/4 wave on a metal ground plane underneath my aircraft - shows a PAW range to 3 local Ground Stations over a fairly long flight over and around Edinburgh at ‘not above 2000ft’ of 29, 39 and 51Km.
From the number of ‘pings’ received, your PAW was obviously transmitting, though I might have expected a much higher ping report at close range from Colchester (mine reported 2372 pings from my ‘Home Airfield’ at <10Km during the period of approach and landing), but that of course depends how long you were in the vicinity. How long was your flight and how long were you within 10Km of Colchester?
BTW, I should have said - PAW Ground Stations only transmit in response to a signal from a PAW-equipped aircraft - though not necessarily your own.
As the OGNRange site clearly shows that PWUKWRM was receiving PAW traffic from up to 30Km yesterday, it seems obvious that, despite your external antenna, your installation isn’t operating to the expected level.
This is probably (at least in part) to do with losses in the coax, but that may not be the whole story. You say you checked your antenna setup with your VNA - I assume testing the antenna in situ underneath the aircraft on the 2m length of RG174. What sort of results did you get?
Other areas to check are that there is no short circuit between the ground and the inner of the coax at the SMA connector, that the PAW Bridge is properly seated in place (are we talking Rosetta or Classic?) and that you had a solid reliable GPS fix throughout the flight - as otherwise your PAW won’t transmit. If you were running SkyDemon, you should be able to see any GPS disconnects from your SD track log. BTW, do you run a transponder? If so, how far apart are the antennas?
If all else fails, we can ask Lee to analyse your track log (when he comes back) to see if that shows any other issues.
* F4406A BTW is the default Hex ID - allocated based on the MAC address of your PilotAware. You should replace this in PAW/Configure with the allocated ICAO Hex ID for your aircraft.
Best Regards
Peter
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Supplement to above,
Lee is of course correct - at least 2dB loss at 869.5MHz in your RG174 cable + 1dB for each additional connector. That means at least half the signal (in each direction) is disappearing in the coax.
Also just checked the length of a PAW ‘Rohan’ 869.5MHz 1/4 wave - the ‘whip’ is 70mm from where it comes out of the body to the tip - and it matches at about 1.3:1 on 2m of good quality (LM240 or CLF200) coax with SMA and BNC connectors.
With reference to your comments on Uplink vs Downlink, the PAW maximum legal transmit power is the same in both cases i.e. 500mW ERP (Effective Radiated Power), so transmit and receive should be pretty much the same either way. We can only use fairly low gain antennas on the PAW side of the ground station to counteract cable and connector losses, whereas on the OGN and 1090 side (which are receive only) no such restriction applies.
Regards
Peter
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Thank you all again.
Peter, your 70mm measured length for the PAW antenna sounds good. Mine, with a different construction, worked out at 66mm. I will have to quiz my chum on the provenance of his long ones, but I’m sure he said they came from PAW. I’ll recheck my own antenna tuning and post a couple of VNA plots later for interest.
I was working on a loss of a little under 2dB for my (perhaps temporary) RG174. But even CFL200 would be 0.6 dB so I’m probably less than 1.5 dB worse. You’d expect this to cause only a 15% loss of range so surely this is not really a major factor here? Of course the RG174 is not so well screened against interference but I don’t think this is the issue either. For test purposes I can probably reduce mine to only 30cm so will give that a go anyway to rule it out. My earlier tests using the directly mounted sleeve dipole were also similarly poor.
I was probably within 10km of PWUKWRM for 15-20 minutes. There were no GPS failures, looking at Skydemon and PAW logs. I have a mode C transponder, antenna is probably 1 m away. I’m fairly sure it isn’t affecting things since I did at one stage pinch its antenna to feed PAW for a quick test!
I see the groundstation antenna gain is +7dBi, I thought it would be more. So the uplink will be at most 3-6 dB worse off than the downlink i.e. uplink range should be at least half the downlink. Certainly not what I'm getting! I agree something is well off in my system.
Alan
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Alan,
All OK on your figures. I would certainly expect to see a bit better coverage from a 15 x20 minute stint. That’s not to say of course that PWUKWRM is optimal in all directions - it could well suffer from some local screening - hangars, trees, etc. I have never been there so wouldn’t know.
You didn’t say if your PAW is a Classic or Rosetta?
Peter
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Sorry, it's a Classic. And it's secondhand so before you say anything that obviously that gives rise to a line of thought! But the fact that it has received an aircraft at 30km but can't receive a ground station at > 3km or so makes me think it's not a basket case. Also, not wishing to add further confusion, but I did dabble with the SoftRF DIY project last year with very similar results. It's this conflicting evidence that is making diagnosis difficult.
Alan
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I have also found that there is a significant difference between a PAW air to Air contact and Air to Ground station.
Initially I thought that it is that 'downward angle' and blanking by the aircraft structure, but at say 3,000ft and 15nm, the down slant is only 1.9 degrees,
so the antenna is getting a good view of stations in at least a 180 degree forward arc.
The antenna is the 'official PAW dipole with about 1.2m coax suckered to the windscreen.
I doubt if a 2db coax loss is the reason for only getting a 2nm range that the Op has reported.
Deker.
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Hi Deker,
OK on the down slant angle. As I reported earlier, the database shows that while Alan was ‘seeing’ the Ground Station reporting at 2nm, the database reports that the Ground Station was receiving him at up to 12Km for at least part of his flight. It still remains a fact that the majority of issues regarding transmission/reception range as you know come down in the end to antenna choice and placement, especially with the relatively low power we are using. Unfortunately, during recent tests, I have found considerable variation between some of the early PAW antennas, which certainly won’t help, though Alan is now using a ‘Homebrew’ 869.5 antenna mounted underneath his aircraft, albeit on 2 metres of RG174.
Alan,
FYI, just so you know, Deker makes the PAW Rohan P3i antennas for us, so also knows what he is talking about.
OK on dabbling with SoftRF - that doesn’t make you a bad person - I’m always ‘tinkering’ with something or other. The reason I asked is because older Classics sometimes display particular faults that we just don’t see on Rosettas. If you choose to run a second hand Classic, that’s perfectly fine with me, as long as it’s licence key is up to date. If it isn’t of course it certainly won’t work!
The ‘obvious’ suspect for a P3i fault would appear to be a Bridge issue, and I certainly wouldn’t rule it out - especially with an older unit, but the PAW Bridges are generally very reliable and Bridge faults are extremely rare. The more likely issue with the Classic would (as I alluded to earlier) be loss of GPS, which precludes P3i transmit and can be caused by a defective GPS dongle or a seriously overheating SDR (the black Realtek ones used on the Classic occasionally run very hot - especially as they get older, - or a faulty WiFi dongle - either of which can in a ‘perfect storm’ situation block the GPS signal, but you don’t appear to be experiencing either of these problems. My intuition (and experience) still directs me to address the antenna / coax issue first, before we start to suspect anything more complicated.
Best Regards
Peter
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I experience the same effect & when checking the log files on aircrew.co.uk the ground station beacons only light up at very close range.
Are there any PAW classic users picking up ground stations at long range?
It feels like I am not benefiting from the atom grid in flight.
Log file here
https://www.icloud.com/iclouddrive/0_XLgLjbxcx_48am7f7ghxExw#2020-08-08_09-30
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I'm doing various range tests, ground and air, in both directions to try to figure out why I see relatively poor performance despite what I think should be a good antenna installation. I thought I should first check my bridge is working OK. According to my test gear, mine is outputing a little over 200mW. Is this correct? I imagine it is as we should be allowing for some antenna gain to remain within the 500mW ERP limit.
TIA
Alan
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OK, so the power output is a big secret! Another question:
A few people have kindly sent me track files in order to evaluate their uplink performance. One set in particular is surprising as the installation is known to have a good downlink but the uplink is apparently dire. Pending a test flight, could someone tell me whether the appearance (or not) of a ground station in the track log, and hence on the Aircrew playback, is affected by the horizontal and/or vertical filter settings for aircraft targets? Similarly, the appearance or not of tower symbols and the OGN-R label on the radar display?
If they are filtered from the log, I would suggest that they should not be, as this precludes post flight analysis.
Another suggestion: I just realised that the log doesn't seem to include the ownship ID, is that on purpose? It seems it would be handy to have.
Alan
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I have recently updated some of my lab equipment, so can cover RF up to 6GHz now. This enables real time and swept frequency analysis, plus all the normal power measurements etc. Quite interesting now being able to "watch" frequency hopping systems working in real time.
I guess I could renew my PAW licence and test a unit I have here, unless Lee would like to issue me a short term testing licence?
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Hi Alan,
Unfortunately the data in the track file is not nearly sufficient for the analysis you are trying to do, internally we have been adding detailed telemetry data for communications between ground/air, and behind the scenes the dev team is working vigorously to categorise the disparate set of installations and rationalise why some installations seem to undergo RF asymmetry, we have some ideas, but much too early to make any kind of definitive statement.
The real benefit here is that data is King, and we have harnessed more data than you could shake a stick at in the months since the launch of the ATOM/GRID network. In fact not only for PilotAware equipped aircraft, but additionally for all those Transponder, Flarm and cap1391 devices.
Nonetheless, we are actively working to constantly improve performance of the system, and there are many ways to do this by changes to software, hardware and even at the system level.
The work that is ongoing is both challenging, and exciting - and as my good friend Alan Walker told me many years ago "You will solve these problems ..."
Thx
Lee
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Lee,
Thank you, but I would still be grateful for a answer to the question! Am I being unreasonable? Like the power question it can be determined by experiment if necessary.
Alan
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Hi Alan
The design of PilotAware meets ETSI EN300-220 at 27dbm.
If you think there is an issue, we will happily investigate, if there is a fault, and product is still under warranty this will be free of charge
If out of warranty, then there will of course be a charge for labor, and any necessary parts
you can send an email to support@pilotaware.com, and we can provide further information on costs and return information
Support Team
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I'm doing various range tests, ground and air, in both directions to try to figure out why I see relatively poor performance despite what I think should be a good antenna installation. I thought I should first check my bridge is working OK. According to my test gear, mine is outputing a little over 200mW. Is this correct? I imagine it is as we should be allowing for some antenna gain to remain within the 500mW ERP limit.
TIA
Alan
With the caveat that all of this depends on the accuracy and calibration state of your test equipment...
200mW is 23dBm. So a little over, say 225mW, is 23.5dBm. Add the supplied antenna gain, which I think is 3dBm, we get 26.5dBm. The EIRP limit is 27dBm so that looks about right. Naturally there are also cable losses too, the measurement method, and the accuracy and calibration of the equipment all come into play. I'm assuming you have measured any loss of the DC block, pad, the cables used etc. at at that frequency too and taken them into account?
On the basis of 'a little more than 200mW' which is assumed is direct from the output of the PAW itself, that PAW would seem to be fine. I also presume the frequency was OK too, I guess it might have drifted a little over time?
Perhaps measure the RF output at the antenna connection point on the aircraft itself?
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JC: I agree with your numbers and conclusion, thank you. My trusty HP8594E has not been calibrated for a very long time, but it gives the "expected" answers for my FLARM, SoftRF and various balloon telemetry units I've built myself so I am pretty confident in it. Be good to get confirmation though, if you get a chance.
Lee: the question I was referring to was about the filtering of groundstations by range/height difference in the log. My filters are set very broad at the moment and I appear to see a log entry for every packet received from groundstations which is surely all that is required to fully analyse the performance of my own equipment? What am I missing? However if the groundstations are filtered, as I suspect, then that would explain why I see such poor uplink results on other peoples' logs and why I suggested they should not be filtered.
Alan
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JC: I agree with your numbers and conclusion, thank you. My trusty HP8594E has not been calibrated for a very long time, but it gives the "expected" answers for my FLARM, SoftRF and various balloon telemetry units I've built myself so I am pretty confident in it. Be good to get confirmation though, if you get a chance.
Alan
Thanks to Lee for getting me up and running again.
I get 22.45 dBm at 869.526733MHz from my *very* old bridge board. But I have -1.03dB of loss in my cable, DC block, and 20dB PAD at that frequency. So the adjusted power is 23.48 dBm. Pretty much as expected really.
If I assume it's a 25kHz wide channel (max allowed under the ETSI spec), the total power available in the channel is 27dBm for each ~15ms transmission pulse every ~1.7s - so looks to be exactly to spec. The 3dB "gain" of the end fed dipole will direct more RF energy to a more horizontal plane. After all an antenna doesn't amplify a signal, the gain is all to do with directing more of the fed RF power compared to an Isotropic antenna. For the end fed di-pole, this means the RF pattern is more of a ring donut shape than a sphere.
I'm not a RF bod by any means, that is a very specialised area. I can just about keep up with what I need to for the projects I'm involved in.
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JC: Super, thanks, so all as expected on the power front.
On the filtering issue, I had a test flight today (actually 2 flights, as when I tried to change the config in the air the dreaded "Http: Get request method not supported" struck again. I had a lot of trouble with that initially but it seemed to have gone away).
I'm now pretty sure that:
1) Range filter settings do NOT affect the label showing the number of OGN-R stations displayed.
2) They DO control whether ground stations are displayed on the RADAR screen.
3) They DO control whether the ground station uplink status is recorded in the track file and hence are available for post-flight analysis.
I think (1) is obviously fine, (2) is a matter of taste, but (3) is surely not what's wanted?
Despite not changing anything, I do now seem to be getting better range performance, although it is inconsistent. I'll write more later when I have gathered more data.
Alan
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Thanks Alan, that's interesting news & I hope this behaviour can be changed in a future version.
Whilst accepting there are other points of view, I now post mine as feedback to the PAW development team:
Until EC is mandated I prioritise look out & listen out, so audio warnings are my primary PAW channel (with a mute switch), I do not want to monitor the radar screen which detracts from lookout.
Continuous ATOM grid reception will maximise my EC detection capability and I was trying to monitor this using aircrew.co.uk track analysis which lead me to believe that my uplink capability was dreadful (I had my filters set to close range detection).
Please would the team consider other ways for users to monitor their uplink status - ideally for me the option for a discrete audio prompt, perhaps every 5 minutes, "Atom".
Perhaps there's a better way & perhaps I'm a minority but it's constructive feedback which is a good thing!
The atom grid really is the key to effective cross platform EC.
Thanks to the PAW team & best regards to all,
Roger
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JC: Super, thanks, so all as expected on the power front.
On the filtering issue, I had a test flight today (actually 2 flights, as when I tried to change the config in the air the dreaded "Http: Get request method not supported" struck again. I had a lot of trouble with that initially but it seemed to have gone away).
Urgh, this is Android right ?
An Android update came out which caused this - it is fixed in the release to be put out literally within a week or two.
I'm now pretty sure that:
1) Range filter settings do NOT affect the label showing the number of OGN-R stations displayed.
2) They DO control whether ground stations are displayed on the RADAR screen.
3) They DO control whether the ground station uplink status is recorded in the track file and hence are available for post-flight analysis.
I think (1) is obviously fine, (2) is a matter of taste, but (3) is surely not what's wanted?
Regarding the track file, it is not really intended as a full diagnostic tool.
We are adding lots of telemetry data in the next release to help do that across the board.
Despite not changing anything, I do now seem to be getting better range performance, although it is inconsistent. I'll write more later when I have gathered more data.
Obscuration plays the biggest part here which is what we have determined.
If you PM me with your flight details I can take a look at our records
Thx
Lee
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Urgh, this is Android right ?
An Android update came out which caused this - it is fixed in the release to be put out literally within a week or two.
Yes, so that's great news, although it's a 2013 Nexus 7 with a very old Android version so maybe not the same issue. Look forward to the new release.
Regarding the track file, it is not really intended as a full diagnostic tool.
We are adding lots of telemetry data in the next release to help do that across the board.
It may not be the intention, but if you did then it would be a very powerful diagnostic tool and I can't see any downside at all. How else is one to assess what's going on other than by staring at the screen during the flight? Will your new telemetry be available in detail to each user for their own aircraft or will it be for internal use for overall statistical purposes? If not then that would of course still be very interesting from a system point of view, but really serves a different purpose and is presumably dependant on the downlink. It seems quite a fraught way to achieve something that would be directly available in the log file for each user.
Obscuration plays the biggest part here which is what we have determined.
If you PM me with your flight details I can take a look at our records
Thanks, will do.
Alan
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Regarding the track file, it is not really intended as a full diagnostic tool.
We are adding lots of telemetry data in the next release to help do that across the board.
It may not be the intention, but if you did then it would be a very powerful diagnostic tool and I can't see any downside at all.
Support mostly, our resources are scarce, and we must be very careful where we spend them
How else is one to assess what's going on other than by staring at the screen during the flight?
Automation of data collection and processing, followed by data representation.
it is not viable to have anybody trawl through megabytes of text logfiles trying to understand the meaning.
Will your new telemetry be available in detail to each user for their own aircraft or will it be for internal use for overall statistical purposes?
initially internally, but the goal is to use the data in order to provide feedback to users of installations where we can clearly see something is not representative. This includes all sorts of things such as the S/W version being run to the quality of the bidirectional datalink
If not then that would of course still be very interesting from a system point of view, but really serves a different purpose and is presumably dependant on the downlink. It seems quite a fraught way to achieve something that would be directly available in the log file for each user.
For the beta released currently being trialed it is working very well across the entire network, we are gathering very valuable information.
There are a few dedicated individuals (such as yourself) who are prepared to invest time and effort into the detailed technicalities of what is going on by trying to analyse the data from the perspective of the individual installation, that is the exception, and not the rule. We need to be able to carry out these tasks using a system level approach, requiring no intervention from the end user.
This is exactly what is happening now, for those individuals flying with the beta release, and will be extended when this goes live.
thx
Lee
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Until EC is mandated I prioritise look out & listen out, so audio warnings are my primary PAW channel (with a mute switch), I do not want to monitor the radar screen which detracts from lookout.
Continuous ATOM grid reception will maximise my EC detection capability and I was trying to monitor this using aircrew.co.uk track analysis which lead me to believe that my uplink capability was dreadful (I had my filters set to close range detection).
Please would the team consider other ways for users to monitor their uplink status - ideally for me the option for a discrete audio prompt, perhaps every 5 minutes, "Atom".
Perhaps there's a better way & perhaps I'm a minority but it's constructive feedback which is a good thing!
The atom grid really is the key to effective cross platform EC.
Thanks to the PAW team & best regards to all,
Roger
Hi Roger,
If you are talking about the 'Positional Contacts Settings' Range Filters in PilotAware, these will certainly affect the display of Ground Stations with the current versions of PAW and SkyDemon software, because SD has historically treated PAW Ground Stations as 'Traffic', but developments are in hand which will significantly improve this situation. In any event, these particular filters are only intended to be used with display software which doesn't incorporate its own horizontal or vertical traffic filters. For systems such as SD, which do, these filters should be left at the default - 'Display All' - and the filters in the display software used to determine what is (or isn't) displayed.
Hope this helps.
Best Regards
Peter
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Thanks Peter, I had not realised that.
However, I monitor audio from PAW and SD and do not want to receive audio warnings about distant traffic.
(PAW audio seems superior to SD traffic related audio.)
Ideally I would like to filter traffic separately from ground stations.
Roll on the new developments.
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Roger,
You shouldn’t get PAW audio warnings for ‘Known Position’ traffic from further out than 10Km and +/- 2000ft and can reduce this to 7, or even 3Km (with comparative relative altitudes) by using ‘Positional Contacts Settings - Select Audio Warning Zones’ in the ‘Positional Contacts Settings’ section on PAW / Configure.
Audio warnings for ‘Bearingless’ traffic are controlled by your chosen setting in ‘Mode C/S Horizontal Sensitivity’. The normally recommended ‘Short’ or ‘Medium Range’ should start to produce Alerts at somewhere between about 3 - 5 miles (approximately - as this depends on lots of variables at each end of the transmit - receive link). The exception is the known anomaly of high power (CAT) transponders, which at up to 500 Watts at the antenna, can trigger audio alerts from significantly further away, - though these normally present a clearly recognisable ‘signature’ as they tend to go straight to ‘Traffic Danger’ without prior warning, or very rapidly through ‘Traffic Notice / Alert / Danger’ - while still outside normal visible range.
Hope this helps
Best Regards
Peter
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Yes, very helpful thanks Peter,
I always found those settings slightly confusing & now I understand them just before the update. ;D
Hope to update & test fly with new antenna tomorrow.
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Lee,
Thank you for that detailed reply earlier regarding the filtering out of ground stations in track logs. Unfortunately I can only agree with a little of it. Of course I sympathise with your support loading, and clearly if you can automate some of it that would be a good thing, but by depriving people of an easy way to sort out their own installation I’m not convinced you are making it any easier for yourself.
Clearly I can’t tell from your rather general description what you’re actually proposing to provide from the telemetry you’re gathering. I’m sure it will be very useful for general system performance monitoring and presumably will provide metrics like “78% of users have contact with a groundstation for 82% of the time” or “your installation scores 7 on a scale of 0 to 10” etc.
I really can’t see how this helps individuals, with all the variability of individual installations and performance of local groundstations to know what they are actually getting, and what to do about it, and I wonder how long it will be before this is publically available in an automated form.
I strongly disagree that allowing people to self-analyse is in any way difficult or undesirable. There is no need to wade through large text files as you suggest. James Roses’ fantastic track analysis tool allows you see in the simplest possible way how well an individual installation is performing in terms of range on various bearings etc. etc. I have suggested to him that it would be even better if the track colour could be changed to indicate where in the flight the uplink was working or not. What could be easier than that? I have made good progress with my own installation, on which I will report in due course, due to this tool.
I really can’t see how some online tool, especially relying on secondary data via the downlink rather the raw data in the track filter, can be any easier or better. People are either interested in knowing how well it works and fixing it, or not.
I cannot see a single good reason why the ground stations should be filtered, and so I do wonder why you are doing it? It doesn’t affect me at the moment as I am using Skydemon audio and set my filters wide, but many people will want to use PAW audio. Why deprive them of the ability to use this facility, for no positive reason?
Please reconsider before your upcomong release! I'm sure it is a trivial mod!
Kind regards,
Alan
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Lee,
I have been asked about the display and reporting of groundstations being affected by the PAW height and range filters, as we discussed on this thread back in August. Is this still the case with the latest software and new log format? There are three questions really:
Do the filters affect the in-cockpit display of groundstations on PAW itself?
Do they affect the groundstation reporting to e.g. Skydemon?
Do they affect the groundstation display on the Aircrew track replay utility?
Unfortunately I can't really check it out myself at the moment!
TIA
Alan
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Do the filters affect the in-cockpit display of groundstations on PAW itself?
Not sure I understand the question ?
Do you mean the web server traffic/radar page ?
The traffic page - no
The radar page - yes
Do they affect the groundstation reporting to e.g. Skydemon?
yes
Do they affect the groundstation display on the Aircrew track replay utility?
yes
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Thanks Lee, but we may be at cross-purposes as I think you are describing filtering of aircraft? I was asking about groundstations. Back in August, we agreed (I think!) that the range and height filters also affected groundstations, so that if somebody set filters at plausible values of, say 5nm/1000feet, then groundstations outside that range would not be seen at all, not in the PAW radar, nor Skydemon nor the groundstation post-flight analysis. This would lead to very pessimistic and incorrect evaluation of uplink range.
I recently repeated that information to somebody but then realised the PAW software was changed radically in Spetember, so wondered if it is still correct? In particular I was interested in the Aircrew replay, as it seems to use the new $PALOG RF entries which may no longer be range filtered?
Hope that's clearer now.
Alan
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Hi Alan
we may be at cross-purposes as I think you are describing filtering of aircraft?
When any object is reported to a navigation device SD etc, it is subject to any filters you apply, so in other words the $PFLAA messages are constrained to within the horizontal & vertical bounds.
There is an additional message for ground stations sent to SD using a bespoke message, this message is also constrained by the same requirements above
if somebody set filters at plausible values of, say 5nm/1000feet, then groundstations outside that range would not be seen at all, not in the PAW radar, nor Skydemon nor the groundstation post-flight analysis.
That is correct if the filters are set to anything other than the default
This is the purpose of the filters, they were actually intended for systems such as some of the glass cockpit systems, which do not have filters.
This would lead to very pessimistic and incorrect evaluation of uplink range.
Agreed, if the evaluation (erroneously) does not take the filters into consideration, then the evaluation is incorrect.
I recently repeated that information to somebody but then realised the PAW software was changed radically in Spetember, so wondered if it is still correct? In particular I was interested in the Aircrew replay, as it seems to use the new $PALOG RF entries which may no longer be range filtered?
I think I now see your confusion, the PALOG entries are for internal debug usage only, are not intended for user consumption, and are liable to frequent changes - and yes they do contain some experimental data to capture more information of the surrounding RF environment.
thx
Lee
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Great, thank you. But at the moment then, with the current software version, if using the Aircrew replay tool to view the uplink range (which is really the only way a user can readily do so), will that be affected or not by the filters?
Alan
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if somebody set filters at plausible values of, say 5nm/1000feet, then groundstations outside that range would not be seen at all, not in the PAW radar, nor Skydemon nor the groundstation post-flight analysis.
That is correct if the filters are set to anything other than the default
This is the purpose of the filters, they were actually intended for systems such as some of the glass cockpit systems, which do not have filters.
Well, every day is a school day. I certainly didn't realise that ATOM stations would be treated the same as aircraft as far as filters were concerned. So, if the filters were set as 5nm/1000' then at 2000' I wouldn't receive an ATOM uplink (including METAR, Flarm etc). This means I might have Flarm traffic within 5nm/1000' of me but I'm not going to see it because the 'aircraft' filters are applied to the ATOM stations. I might be 1nm away from the station but at 2000' and won't see any ATOM data! Is that correct? If so then I think that needs a re-think.
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Hi PaulSS, no it's just the display/reporting of the groundstation itself that's filtered, not the aircraft it is uplinking.
Alan
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Hi Paul
To be clear
All the filters control is the display of the position of an object
So if a rebroadcast object (flarm aircraft) is within filter range it is displayed
This is not the same as the ground stations position
Thx
Lee
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Lee, going back to my last question which you perhaps missed, and avoiding internal techie details if you prefer, I still think it is of interest to any user to know whether, if they replay their flight in the Aircrew tool, they will see the in-range uplinking groundstations regardless of the range filter settings?
Alan
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I am also interested in this question.
Vector seems to measure downlink range but my flarm glider avoidance relies on uplink range.
Is that right?
Roger
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Sorry for the attempted thread derail and I am very pleased I misunderstood the system. Back under my stone I go ;D
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Hi,
I'm curious about the uplink range also and had a recent discussion about it on the RVSqn forum.
I used the new Vector tool which showed good 360deg downlink coverage out to between 60-80km. I can also typically see contacts out to 96km on the PAW radar screen in my aircraft (see attached screen shot).
Based on this I had assumed that I was getting good coverage of both:
A) aircraft to aircraft detection (PAW and ADSB traffic) and
B) ground to aircraft detection (FLARM and MLAT) from ATOM uplink.
However if the uplink range is poor / variable then I could be missing B) traffic completely and my PAW radar screen would only be showing me traffic from A)?
Is there any way of determining this, either in-flight or afterwards by analysing track files?
Obviously having a radar screen full of contacts is a step forward from not having any EC, however it would be useful to know for example if I'm missing glider traffic.
Thanks,
Chris.
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However if the uplink range is poor / variable then I could be missing B) traffic completely and my PAW radar screen would only be showing me traffic from A)?
Is there any way of determining this, either in-flight or afterwards by analysing track files?
Hi Chris,
That is the absolute nub of this rather protracted bit of thread. If you download your track file from your PAW, and upload it to this tool:
https://aircrew.co.uk/playback/
then from the comfort and safety of your armchair, rather than peering at your screen in flight, you can see exactly what went on. You will see when you received beacons sent from each of the groundstations (about every 15 seconds unless the GSTN is saturated with other traffic). My caveat (also on the RVSQN) was that with the PAW software in use back in August, these GSTN beacons were filtered out from the track file the same as aircraft, so if you were not careful about how you set the filters (assuming you use them at all) then you might conclude the uplink range was less than it really was. Following that post I realised that the PAW track file now uses a different method of logging the beacons, so what I said about filtering may no longer be true. I'm hoping Lee will answer one way or the other to clear this up, since I can't check it experimentally at the moment for obvious reasons.
Alan
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Thanks Alan,
I reviewed one of my flights from June 2020 using the Aircrew playback tool. I could see all the traffic but not the groundstations, but I'm not sure whether they were being filtered out or I wasn't using the tool correctly.
Most of the traffic seemed to be ADSB which presumably was received directly aircraft to aircraft. I did spot a glider which had "G P U" and PilotAware and Uplink were shown when I hovered over the P and U. Does this mean that its position was coming via uplink or directly aircraft to aircraft from its PilotAware unit? Apologies if this is a stupid question but I'm not familiar with the Aircrew tool.
Any hints tips or instructions would be gratefully received.
Best Regards,
Chris.
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Chris, I would say those GPU targets were uplinked. Did you see any groundstation tower symbols in the replay? I think a tower only appear on the map if at least one beacon has been received from it during at some point during the flight. If so did none of them display green rings around the tower as you got near? This happens for a short time after each beacon packet is received.
I'd be keen to haev a look if you want. You can make your flight public on the replay site and PM me the link (or post it here) or better still just PM me me the file.
Alan
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I have uploaded the flight and made it public. The glider I spotted with GPU is at 09:27 north of my track near Husband's Bosworth.
Here is the link:
https://aircrew.co.uk/playback/458ef337 (https://aircrew.co.uk/playback/458ef337)
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Chris, I'll have a better look at your track later today when I'm on the train, but I can see you had several uplinked targets apart from the glider, but oddly no groundstations displayed. I wonder if you did not have the "Display Ground Stations" box ticked in the PAW configuration?
Alan
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Thanks Alan,
I will need to check my PAW settings next time I'm at the aircraft, I cannot recall changing this setting and the instruction manual does not state what the default setting is for this.
Studying the flight on the Aircrew tool again, I can see most of the traffic was ACSB, which I think is a straight ADSB reception a/c to a/c. I was getting good range on these targets out to ~80nm.
You are correct that there were a few with "U" so I was receiving uplinked traffic. However I cannot tell whether there were so few because the uplink range / coverage was poor or whether there was not much traffic around on this day in this category. I'm suspecting the former since these targets were quite short range and very inconsistent appearing and disappearing often.
The few that I saw were:
- ACSPUM, i.e. Mode-S detected directly with MLAT data being Uplinked
- ACSPU, could be position from PilotAware unit or maybe FLARM uplinked?
- PU, although type is shown as glider, according to the manual this is an OGN-R station uplinked via PilotAware which makes sense since it doesn't move?
I could not see any "F"s for FLARM, but perhaps FLARM position source but uplinked via PilotAware would be displayed ACSPU?
Regards,
Chris.
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Hi Young,
I've looked at the linked playback file and clicked all the aircraft that were uplink or Mlat.
This shows their traces in the horizontal view on aircrew/playback and gives an approximation of uplink 'continuity'.
I'm guessing you had intermittent uplink from Turweston, Husbos and other(s) near peterborough.
Deker
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So would it be worth extending this by getting the maintainers of the mentioned ground stations to look at Vector analysis for PAW for all aircraft?
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Many thanks Deker - that's really helpful :D
I guess there may be a problem with my 869.5MHz reception since three different ground transmitter uplinks were all being received intermittently?
The 1090MHz reception seems to be good since I'm getting good range and few dropouts from ADS-B targets.
Now that I'm learning what to look for, I will study a few of my other flights to check whether the problem is consistent.
Best Regards,
Chris.
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It's also worth knowing that the OGN base station software has been updated several times since July which may help with this issue.
There was a theory floated that an uplink from one station could be stomped on by another therefore only a garble uplink was being received in the air. I think there is now some sort of uplink scheduling between ground stations to help prevent this, so may not be all down to your installation???
I'm still trying to get some flights in myself to do some more testing - not been easy!
Deker
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Hi,
I've analysed a couple more of my flights (ideal way to spend my time on a cold, foggy, Saturday in lockdown ;) )
See attached:
Slide 1 - Bidford to Wadswick 31-Aug-2020.
Slide 2 - Sandown to Bidford 16-Oct-2020.
Both flights show much better range and consistency receiving ADS-B contacts. Once again there were far more ADS-B contacts than uplinked contacts.
Slide 1 - the uplinked contacts were very inconsistent throughout the flight.
Slide 2 - the uplinked contacts were consistent around Basingstoke with gliders detected and staying in contact, however further north near Bicester I only received intermittent glider contacts (although they were further away from my track)
I'm not sure what to conclude, it was reassuring to see that on the later flight I did get some good uplink performance maybe due to OGN base station software improvements or perhaps the transmitter near Basingstoke was better or I was closer to it.
Anyway I will do further investigation next time I fly.
Thanks for all the assistance so far.
Regards,
Chris.
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Hi Chris
I briefly looked at your info, and I would say you were receiving the traffic as peripheral detection
What does this mean I hear you say.
You will only trigger an uplink IF the traffic is within 10km and +/-5000ft of your position
You will receive an uplink IF ANY traffic trigger is activated by any PAW emitter.
So Imagine you are 11km from a Glider X, but another (PAW) aircraft is 9km from Glider X
this will trigger a rebroadcast of Glider X which you will see via peripheral detection
If the other PAW aircraft now moves 10.1km from Glider X - it will no longer be rebroadcast.
This can appear to be intermittent, but this is in fact by design.
Remember you will only trigger aircraft when they are within 10km of you and actually, the full trigger set which have to be met
1. within 10km (horizontally) of a PAW Emitter
2. within 5000ft (vertically) of a PAW Emitter
3. not stationary
thx
Lee
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Thanks Lee, that's good info for me since I wasn't familiar with this peripheral detection functionality.
It also probably explains why I don't see many uplinked contacts if they are only received when within 10km. Also considering that I was flying during the pandemic when there was much less traffic anyway.
Regards,
Chris.
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It also probably explains why I don't see many uplinked contacts if they are only received when within 10km.
Hi Chris
Just to be absolutely clear, 10km is not a receive constraint, it is a trigger constraint
Thx
Lee
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Hi Lee,
I've analysed a couple more of my flights where I there were gliders within 10km. I could see them via uplink from the local ATOM station and the good news is that they were tracked consistently without the dropouts I observed with uplinked traffic further out on other flights.
For info I've attached the Aircrew tracks:.
- On the left I saw 5 gliders ranging from 0.8 to 3.2nm near Hinton in the Hedges,
- On the right I saw 2 gliders on approach to Bidford at 3.8-4.4nm range.
In all cases their tracks were continuous during the time I flew nearby.
I'm happy that this seems to show 869.5MHz reception is working okay in my installation and supports your explanation, thanks. :D
Regards,
Chris.
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Thanks Chris
We should probably start talking about our next development which internally we are calling SKYGRID
basically ATOM network in the air
As part of the Release end of last year, we incorporated additional side messages
Air to Air
Ground to Air
Air to Ground
The Air to Air messages allow a PAW to inform its neighbours, if it is not receiving uplink data
Its chosen neighbour will act as an intermediary, supplying critical traffic information
We have had this all working in simulation and live in the lab, we will start field trials as soon as se are allowed
Thx
Lee
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Wow, you guys don't stop.
Full of admiration.
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I can't believe how much I've had to bite my lip on a certain aviation forum, with a certain anti-PAW poster, knowing that air-to-air was in the offing. This should shut him up, as even he can't argue how useful the Link system was in the military........unfortunately 'should' is wishful thinking ;D
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I can't believe how much I've had to bite my lip on a certain aviation forum, with a certain anti-PAW poster, knowing that air-to-air was in the offing. This should shut him up, as even he can't argue how useful the Link system was in the military........unfortunately 'should' is wishful thinking ;D
Belief is usually strong enough to deny proof, you could simply stop torturing yourself... with an argument that may not be won by the presentation of beyond reasonable doubt evidence.
If you haven't heard it, it goes like the Douglas Adams argument for the non-existence of God. (https://www.goodreads.com/quotes/1187961-the-babel-fish-is-small-yellow-and-leech-like-and-probably)
I made one reasoned argument (to someone editorial) to correct a highly prejudiced PAW review in a certain magazine. The reply was shocking.
The reply also convinced me that when you encounter entrenched beliefs, offered evidence is a waste of time and simply results in an increasingly bloody forehead.
SKYGRID - This is an amazing step, and means that we are entering the realms of an ad hoc network involving moving nodes, if I have got this correct?
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SKYGRID - This is an amazing step, and means that we are entering the realms of an ad hoc network involving moving nodes, if I have got this correct?
Almost, the problem with an ad-hoc network, is the loss of control and coordination
We spent a lot of time working out how to ensure determinism in the system, and this is certainly successful in our prototyping
The system is very smart and totally novel, it works by having predictable designation of the intermediary
This is to ensure multiple intermediaries do not spring up in the network
I think if I gave more away, my colleagues would string me up to the nearest tree ;D
The closest cousin to this would be similar to the token ring network some may be old enough to recall,
As we are going with quotes Steve ;)
I would recommend “The Soul of a New Machine” by Tracy Kidder, staple reading for those who have been involved in the silicon design industry
Nuff said :-X
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Not skynet anyway!
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Thanks Chris
We should probably start talking about our next development which internally we are calling SKYGRID
basically ATOM network in the air
As part of the Release end of last year, we incorporated additional side messages
Air to Air
Ground to Air
Air to Ground
The Air to Air messages allow a PAW to inform its neighbours, if it is not receiving uplink data
Its chosen neighbour will act as an intermediary, supplying critical traffic information
We have had this all working in simulation and live in the lab, we will start field trials as soon as se are allowed
Thx
Lee
I can't quite believe this little nugget has not gone viral and knocked Covid off the top spot. Instead it seems to have raised barely a whimper, and there's poor PaulSS seen wandering around Bembridge with half his face missing from biting his lip.
Lee, you are bloody tease!!
Alan
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It's alright, Alan. Aside from my facial disfigurement, I'm keeping my powder dry for the next whinge about insufficient cover from the ATOM stations. With aircraft able to act as intermediaries, the umbrella of linked information could even, perhaps, shut up ex-RAF navigators......although that might be a step too far ;D
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With the greatest respect may I suggest that any proliferation of how this works and when this is available be left to Lee and the Team.
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By the way, I wasn't getting at anyone it's just that SKY GRID has the potential to be absolutely mind-bogglingly good, and as Alan said "knock COVID of the top slot" - well amongst us pilots anyway. Keep biting the lip. It will be worth the wait. I wonder where we should trial it second. As easy as putting a pin into a map and pressing return I am told.