Vector shows PAW but not ADS-B signals

[Young_C]

Thanks Keith - that's helped my understanding of the Vector plots.

[GeoffreyC]

That front strut is too close to the PAW antenna. I suspect it may be acting as a reflector and improving the signal to the left at the expense of the right.

Many microloghts and Gyros have the coms antenna on the top of the nose, as far forward as possible. Is that an option?

I was about to suggest moving your existing antenna to just inside the outer edge of the upper windscreen - as high up as you can manage, which would clear the immediate (close) obstructions, and help to reduce obstruction to the right rear due to Pilot, Passenger, Pylon and Engine, etc., but have just seen your recent post about dropping the wing for storage, which would make this awkward (though not impossible - it would just involve disconnecting the cable from the antenna before removing the upper screen).

...
WRT your ADSB issues, it definitely looks like a fault to me. Loss of GPS to the Txpdr - would prevent Mode-S/ES transmission, but would also affect PAW transmissions and would be reported as gaps on your Nav System and PilotAware Tracks, so relatively easy to check. Please let us know how you get on.
 

Best Regards

Peter

An update on my PAW and ADSB results from the flight I managed to get in on 2nd January,  probably the last for a while 

I moved the PAW ADSB antennae up as high as I could on the lower windscreen,  so it was half on the bottom windscreen and half on the upper.   PAW Vector was near identical to prior flights.  Having looked at Brian Montilla's trace, his trace doesn't show the right hand 'blind spot' mine does, but his Rosetta is mounted underneath the lower windscreen so has antennae in almost identical position to mine.   This makes me think that its not the front strut that is shielding the signal,  I am wondering whether it is the USB cigarette socket converter for my ipad which is on the opposite side of the front strut from the PAW antennae.
I'll try flights with no power converter plugged in or a different one in use,  somehow I have misplaced the Ankher I was using.

ADSB, no positive progress.  Moved the GPS mouse to above the coaming and didn't see any GPS dropouts on my Trig or Skydemon in flight.   The Vector plot is non existent again, and looking at Flightradar 24 and ADSB Exchange, they both show a patchy flight trace.
Have ordered replacement plug to makeup a new antennae cable for my transponder as first option before I change the transponder antennae.

But next stage of testing these will depend on ability to fly again :-(

Geoffrey

[exfirepro]

Hi Geoffrey,

Thanks for the feedback.

I'd be very surprised if the USB socket and adaptor on their own, or even with the attached cable, were causing such a big gap in transmission to the front right from where your antenna is positioned, but I suppose when combined with the front strut and front wheel (depending on your height/distance from the ground station(s)), between them all they could be. If so the only viable option is to move your antenna higher up on the windscreen or fit an external one below the pod or rear skirt.

Getting back to your original (and possibly more important issue), however - why we are seeing no ADSB from your Trig TT21 transponder.

You are obviously transmitting P3i from your PAW, which means it definitely has a GPS fix (or it wouldn't transmit).

That means the reason for 'No ADSB' has to be down to one of the following: -

1. Transponder is not not transmitting due to a fault.

But you were tracked on FR24 so that can't be the case - though I suspect the tracking was probably from your Mode-S via MLAT.

I am seeing faint signs of a very weak transmission on your ADSB Vector charts - which is probably the TT21 auto-transmitting its Hex ID.

Both of which show that the transponder IS transmitting.

2. Transponder is not receiving GPS Data from PilotAware.

We have already determined that the PilotAware is producing GPS data, and it's very easy to check if this data is being received by the Transponder (you can do this on the ground).

First power up both PilotAware and the Transponder (set the Transponder to 'ALT').

Next, login to the PilotAware Home Screen and check that it has a GPS fix. If it has, press the 'FN' (Function) Button on the Transponder Control Head Twice. This should bring up the ADS-B position monitor screen - which will display local lat/long co-ordinates on screen if the transponder is receiving GPS position data. If they don't appear, or just show 'dashes', there is a problem with one or more of the following. (Note: it's easiest to check the settings first, before starting to take connectors apart).

3. Fault in USB to RS232 cable or settings.

These are likely to be one or more of: -

(i) Faulty Cable (You are presumably using the recommended FTDI USB to RS232 Serial Cable ?), if so, the only cabling fault can be wrong wires used, or the correct wires but connected to the wrong pins in the Trig 25-way connector. The correct wiring is Black Wire (Ground) connected to Pin 4 and Orange Wire (Data Out - From the PilotAware) connected to Pin 5 (these are on the 13 pin row (the other row has only 12 pins) and if you are at the correct end, Pin 1 will have a connection, then Pins 2 and 3 won't - if they do, you're at the wrong end! The most common mistake I find is the Yellow (Data In) wire connected to pin 5 instead of the Orange one.

(ii) Wrong Setup at the PilotAware End.
This can be one of two errors - either the wrong USB port has been set up, or the wrong Baud Rate has been set. Looking at the USB end of the PAW, with the Ethernet Port to the Left of the USB Ports, the USB ports are numbered from the left, 1 then 3 on the top row, and 2 then 4 on the lower row. If you have the standard Classic setup, the 'spare' port which the USB lead to the transponder will most likely be plugged into will be Top Left, which is Port 1. On the Configure Screen, Port 1 should be set to 'Transponder Trig' and 9600 Baud. If it isn't in Port 1, you must identify and then configure the CORRECT USB Port.

(iii) Wrong Setup in the Transponder.
To get to Setup, Hold in the 'FN' button in while switching the Transponder ON. Once the transponder has turned on, release the 'FN' button. Each further press of the 'FN' button moves the unit to the next setting position in sequence. If you don't need to change the setting, simply press the 'FN' button again to move on to the next option. The critical ones you need to find and check are GPS Input - which should be set to NMEA 0183, and GPS/TIS Line Speed - which must be set to the same as you set in PAW - namely 9600 Baud. Once you have checked or reset these correctly, simply switch the transponder OFF then ON again (back to 'ALT') and re-press 'FN' twice to see if the Position Co-ordinates are now showing. If they are then 'Bingo' you have won the prize.

If it's still not working get back to me.

Best Regards

Peter

[GeoffreyC]

Thanks Peter for your advice on checking the transponder and Pilotaware connection.

Went briefly to the airfield yesterday evening,  the transponder head is showing the GPS coordinates from PilotAware when you press FN several times, as I thought it was.

I have removed the transponder body to antennae cable and took it home with the plan to make up a new cable with the plugs I've ordered.  Testing it last night, it appears to have good continuity both on the outside shielding and the inside pin, so thought it might be due to degradation of the shielding over time that was causing the poor transmission quality.

This morning I thought to test the continuity of the inside pin to the shielding,  and I can report that that's showing great continuity as well, barely any resistance at all !

Think I now know the source of the ADSB transmission quality.  I'm sure i was careful to not get any braiding trapped when I shortened the cable, but clearly I must have done somehow.   Will see if I can find and fix it, otherwise will continue with plan A of making up a new cable.

Thanks for all your help and advice

Geoffrey

[Admin]

This morning I thought to test the continuity of the inside pin to the shielding,  and I can report that that's showing great continuity as well, barely any resistance at all !

Yikes!
I hope that has not damaged the power output amplifiers by shorting, might be worth consulting the manufacturer

On a related note, I am happy that the VECTOR service helped identify the issue - even if that is not its main intention!

Thx
Lee

[GeoffreyC]

This morning I thought to test the continuity of the inside pin to the shielding,  and I can report that that's showing great continuity as well, barely any resistance at all !

Yikes!
I hope that has not damaged the power output amplifiers by shorting, might be worth consulting the manufacturer

On a related note, I am happy that the VECTOR service helped identify the issue - even if that is not its main intention!

Thx
Lee

It did indeed thanks Lee, I would probably have been none the wiser on this issue other than perhaps some ATC's reporting poor visibility of my transponder.

Peter's useful guide to checking the PAW to Transponder connection,  and then mine to check the continuity (or not) of the cable might be worth writing up somewhere.

I'll makeup a new cable and will have to wait until can fly to try it out.   Don't think at the moment I can make provision for this as urgent flight safety,  maybe when lockdown starts easing.

Thanks again all

Geoffrey

[Young_C]

Hi all,
I have a couple of related questions regarding the new Vector tool.
1. Does selecting "PilotAware" from the Type pulldown show the polar diagram for transmissions from my aircraft to ground stations using the 869.5MHz PilotAware antenna?
2. Does selecting "ADS-B" from the Type pulldown show the polar diagram for transmissions from my aircraft to ground stations using my existing transponder's 1090MHz ADS-B out antenna?

I'm interested because from the Vector plots I can see much better performance with 1. compared with 2. Whereas when I look at my reception performance (using track files) I see much better 1090MHz reception (albeit this would be using the PilotAware ADS-B in antenna) compared with 869.5MHz reception from ground station uplink.

I'm not an expert, but trying to understand since it seems counter-intuitive to me.

Thanks,
Chris.

[exfirepro]

Hi all,
I have a couple of related questions regarding the new Vector tool.
1. Does selecting "PilotAware" from the Type pulldown show the polar diagram for transmissions from my aircraft to ground stations using the 869.5MHz PilotAware antenna?

Yes Chris, that is correct. Provided you have selected your own aircraft by its ICAO Hex ID, the VECTOR report shows the transmission performance of the selected Mode from your aircraft as received by PAW ATOM-GRID Ground Stations along your route* from data gathered from however many flights you have made over the previous 30 days.

 *Providing you have flown within range of at least one of these stations on each flight.

2. Does selecting "ADS-B" from the Type pulldown show the polar diagram for transmissions from my aircraft to ground stations using my existing transponder's 1090MHz ADS-B out antenna?

Again, yes that is correct, providing you have ADSB out enabled via a GPS feed into your transponder. Those using a CAP1391 Device (such as SkyEcho2) to provide ADSB instead of via a transponder need to select CAP1391 as the desired Mode.

I'm interested because from the Vector plots I can see much better performance with 1. compared with 2. Whereas when I look at my reception performance (using track files) I see much better 1090MHz reception (albeit this would be using the PilotAware ADS-B in antenna) compared with 869.5MHz reception from ground station uplink.

I'm not an expert, but trying to understand since it seems counter-intuitive to me.

Thanks,
Chris.

Chris,

Assuming we are talking about RVAH, I agree - the plots do appear to indicate significantly better transmission coverage from your PilotAware than from your transponder.

Remember, however, that what is shown always depends on your installation - in particular the position in your aircraft of your devices and antennas # and - especially with a low flight density - on how 'visible' you were to the Ground Stations along your route. Apart from the setup in your aircraft, this can also be dependent on your flying height and ground topography. Remember also that ADSB range reporting is deliberately limited to 60Km to limit the amount of data which has to be processed to generate the reports. The most important thing to determine is whether we are achieving good all round cover through 360 degrees. Unless extremely poor, range is initially of far less significance.

 # Again assuming we are talking about RVAH, I have seen your installation video and can't see any issues which would reflect poor indicated coverage to the RH side of your aircraft, though we need to look specifically to see what stations you were reported from (I am aware that you have posted data on another thread which I will take a look at to see if there is anything obvious).

Regards meantime

Peter

[Young_C]

Thanks Peter that's helpful and it's great that Vector is helping me to understand and fine tune EC performance of my aircraft RVAH,

I think there are two issues which I'm exploring:
1. ADSB-out from my transponder is a bit uneven (better to left than right) and the range is not as good as the PilotAware-out.
2. PilotAware-in directly from ADSB contacts is significantly better than PilotAware-in via uplink which appears to be intermittently / short range.

I'm more worried about issue 2 (which I've raised on the other thread "OGN-R uplink typical range") since I fly from a gliding airfield and don't want to be missing glider traffic.

Regards,
Chris.

[exfirepro]

Hi Chris,

I have just had another look at your PAW install pics and video on the RV thread (very neat installation BTW - which undoubtedly accounts for your excellent PilotAware transmission performance). The pics and video however also confirm my suspicion that your transponder/ADSB Out antenna (the Narco blade-type one) is IMO poorly positioned just inboard of your right-hand undercarriage leg, where it will be significantly screened to the right-hand side by the leg, fairing and wing and also to the front-left by the exhaust/cowling (as borne out by your 1090MHz Vector plots).

WRT your PilotAware Uplink issues, I concur with Lee’s posts on the other thread that this is much more due to lack of traffic and distance/bearing from the Ground Stations you have flown past than any problem with your installation. I would certainly expect you to see gliders locally on your way in and out of Bidford as it has it’s own ATOM Station, though Vector shows a significant gap in its PilotAware coverage to the north (from about 300 to 080 degrees), though this may again be due (at least in part) to lack of recent traffic.

Hope this helps.

Best Regards

Peter

[Young_C]

Thanks Peter,
I think you are correct on the position of the 1090MHz Narco antenna from my transponder. That would explain the worse performance to the right.

Also understood on the uplink issues, I will re-analyse some of my track files in and out of Bidford to make sure I was getting good uplinks of glider traffic within 10km.

BTW interested that Vector could be used to review the transmission pattern from an ATOM station. What do you type into the ICAO code to get this? I tried PWBidford and it obviously did not work!

Regards,
Chris.

[exfirepro]

Hi Chris,

Ah.. That's because at the moment the Ground Station Analysis is only available to Station Maintainers through their secure login (and of course to the Development Team).

I have attached a PilotAware coverage screenshot for PWBidford taken just now but which only includes data from a total of 7 days between 11/11/20 and 05/01/21. Happy to take a look at any other specific stations for you.

Best Regards

Peter

[Young_C]

Thanks Peter - that's interesting.

For such Vector plots for an ATOM station does the pattern represent transmissions picked up by other ground stations or other PAW units on aircraft? If it is the latter then I would expect more contacts to the South of Bidford since the circuit pattern is on this side.

Regards,
Chris.

[steveu]

For such Vector plots for an ATOM station does the pattern represent transmissions picked up by other ground stations or other PAW units on aircraft? If it is the latter then I would expect more contacts to the South of Bidford since the circuit pattern is on this side.

Hi Chris,

I wasn't going to put up any Vector plots before PAW HQ say I can, but you can see rough coverage in the public domain for all aircraft into a ground station in a nice pretty picture. Use gliderradar and pull up the PAW side of the ground station and ask for coverage in the sub menu that pops up.

In the attached the red line is the runway at Headcorn.

https://www.gliderradar.com/center/51.12464,0.53833/zoom/10/time/15

[Admin]

One of the non obvious issues is airspace
You see blank areas to the north of Bidford and Turweston, due to Birmingham airspace

Thx
Lee