Vector shows PAW but not ADS-B signals

[Young_C]

Thanks Steve - that's a great tool and gives a good picture of the ground station coverage.

[exfirepro]

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

For the avoidance of doubt or confusion, when I commented on Bidford’s Radiation Pattern above, I was well aware of the proximity of Birmingham airspace to the North East of Bidford and agree that would obviously limit the range of expected PAW traffic in that direction, but under ‘normal’ circumstances I would expect to see a fair density of PAW traffic routing through the obvious ‘gap’ between Bidford and Birmingham whilst avoiding controlled airspace en route to and from Wales and the North West and the East Midlands / South and East. I have personally used this route in both directions on several occasions in the past.

That’s why I took care to advise that the chart is based on a small number of records from only 7 flying days in the middle of a pandemic, so on this occasion almost certainly only illustrative rather than truly representative.

Best Regards

Peter

[exfirepro]

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

Hi Geoffrey,

I had a long chat on the phone to one of my contacts in Trig Technical Support this afternoon. She confirmed that the output of the TT21 is protected, so hopefully all will be well once you fit your new cable.

Best Regards

Peter

[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 !

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

Hi Geoffrey,

I had a long chat on the phone to one of my contacts in Trig Technical Support this afternoon. She confirmed that the output of the TT21 is protected, so hopefully all will be well once you fit your new cable.

Best Regards

Peter

Thanks Peter, that's useful to know.  Good old Trig.

I think I know the source of the original problem which was fitment of the BNC cable onto the existing antennae cable,  the outer shield was crimped onto the outer rubber sleeving and not the wire braid inside, so when the BNC was plugged in it could push the pin backwards partly out of the plug and cause it to short on the outer shielding.
Although I could re-make this one to be more secure I've made up a whole new cable and thoroughly tested it for continuity in the right and wrong places.   Its waiting in the car boot to take it and fit back to my plane.

Miserable foggy weather today so not like I'm missing anything,  but yesterday was clear and I heard the sonic boom from the Typhoon jet from Coningsby as it rushed to intercept an errant German pilot that had lost comms.  We should check their Vector plot !

Cheers, Geoffrey

[steveu]

I think I know the source of the original problem which was fitment of the BNC cable onto the existing antennae cable,  the outer shield was crimped onto the outer rubber sleeving and not the wire braid inside, so when the BNC was plugged in it could push the pin backwards partly out of the plug and cause it to short on the outer shielding.
Although I could re-make this one to be more secure I've made up a whole new cable and thoroughly tested it for continuity in the right and wrong places.   Its waiting in the car boot to take it and fit back to my plane.

Some BNC connectors have inner pins that locate with a positive click in the housing. There isn't a lot of force on the inner pin when inserted into the socket AIUI.

It's worth using a template when trimming the various insulation layers and the inner and outer conductor for a crimp connection BNC. These may be provided by the manufacturer and consist of measurements to strip to.

[CliveJ]

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).

Best Regards

Peter

Hi Chaps, just reading this thread and was interested in any recommendation you could make on what to do with my Transponder antenna position. I read the comment above ref the positioning of the Narco antenna and that is exactly where I have mine, also seeing some blanking from what I assumew is the U/C legs/wings.

Where on a metal low wing aircraft (mines an RV9) is the best place to permanently install the antennas?

I have the three underneath, PAW in and out are currently in a temporary position in the wing root fairings, TXP in the 'standard' RV position.

Thanks Regards, Clive

[exfirepro]

Hi Clive,

Antenna fit positions on aircraft are often a compromise between the ideal and what is physically achievable.

With a low wing aircraft with fixed undercarriage like an RV, I'd suggest ideally as far back on the belly as possible away from the undercarriage legs, so that the angle(s) obscured by the legs, etc. are as narrow as possible - especially towards the front of the aircraft, but not so far back that the body of the aircraft itself becomes a significant obstruction towards the front - such as might be the case with a high-wing aircraft like a Cessna or Foxbat, where the antenna(s) need to be mounted on the lowest part of the belly, not the slope up towards the empennage - even though this may require a compromise in relation to the undercarriage. Remember also that most RADAR or other receiving stations we are interested in will be below us. Don't worry too much about aircraft flying in from above. Signals between you both will normally be detected well before obscuration by the aircraft bodywork becomes a problem.

Having said all that, of course the position chosen has to be accessible to facilitate the antenna installation. For each potential mounting site, you need to envisage how much will be obscured through 360 degrees from that point. I would also suggest discussing your chosen 'potential' options with your inspector before going ahead with a fit. Compromise is usually necessary in most cases.

Oh, and if the chosen position requires long cable runs, remember to use high quality coax matched to the signal frequency to minimise losses.

Hope this helps.

Best Regards

Peter

[GeoffreyC]

I think I know the source of the original problem which was fitment of the BNC cable onto the existing antennae cable,  the outer shield was crimped onto the outer rubber sleeving and not the wire braid inside, so when the BNC was plugged in it could push the pin backwards partly out of the plug and cause it to short on the outer shielding.
Although I could re-make this one to be more secure I've made up a whole new cable and thoroughly tested it for continuity in the right and wrong places.   Its waiting in the car boot to take it and fit back to my plane.
...
Cheers, Geoffrey

First flight today after lockdown, unfortunately I missed the good weather as I was away earlier in the week, so it was decidedly lively for my check flight today.

To try to isolate the cause of the front RHS blind spot on PAW I tried flying without the Anker plugged into the USB socket by the front strut.

Looking at the Vector diagrams after what was a very local 30 minute flight it does seem to still have the front right gap, so suggesting its the front strut rather than the Anker.  Most traces from 10km away but encouragingly some traces up to 40km.  When I get the chance for longer flights I'll see if this bears out.

And I now have ADS-B working now and appearing on Vector as well,  and on https://globe.adsbexchange.com/?icao=405f7f&lat=52.148&lon=-0.311&zoom=12.9&showTrace=2021-04-01 the trace is absolutely rock solid, no gaps or faint lines at all, so the new Transponder to Antenna cable did the trick.

Cheers, Geoffrey

[Smaragd]

Flew yesterday with my new Sky Echo 2 as well as PAW; 3 flights Garston Fm-Devizes-Lyneham-GF, up to 4000',  to compare different positions of the SE2. Vector plots of the 3 flights combined given below for PAW and SE2. Very impressed by PAW coverage (though there's room for improvement in some sectors): 8 stations in total (Wadswick, Shirenewton, Calne, Clench, Kemble, Oxford, EGVL, Enstone, with at least 4 most of the time. SE2 results significantly thinner. Referring back to earlier messages on the thread, is this because quite a few of these ATOM stations don't have ADS-B In capability (is this listed anywhere?), or should I be wondering about the performance of my SE2?

[steveu]

On the SE 2 web page, this is the claim:

With 20W transmit power, your 1090MHz ADS-B signal can be received up to 40NM away.

So, the limit seems to be 40NM, or 74km.

You're getting some pings up to 40km,and the occasional towards 50km, looking at your diagram?

You don't say if your PAW is using the integral, internal or external aerials, or what sort of aircraft it is, metal, wood or rag & tube?

[Ian Melville]

... Referring back to earlier messages on the thread, is this because quite a few of these ATOM stations don't have ADS-B In capability (is this listed anywhere?)...?

I thought all ATOM stations had ADSB in? Some early OGN-R stations may not and this needs to be addressed if possible.

[Smaragd]

On the SE 2 web page, this is the claim:

With 20W transmit power, your 1090MHz ADS-B signal can be received up to 40NM away.

So, the limit seems to be 40NM, or 74km.

You're getting some pings up to 40km,and the occasional towards 50km, looking at your diagram?

You don't say if your PAW is using the integral, internal or external aerials, or what sort of aircraft it is, metal, wood or rag & tube?

Low wing, wood and fabric. Classic PAW, internal aerials, central on the coaming. SE2 in 3 positions: coaming RHS, central behind me near canopy, canopy RHS low. (to keep it vertical). On PAW playback grid, not a lot of difference between the SE2 playback for the 3 positions, but some breaks compared with PAW. On FR24 the addition of SE2 shows tracking to a much lower height on take-off/landing compared with previous Mode S only. Of the 8 PAW stations which tracked me (for at least some of the time), 5 were within 22nm the whole time, the other 3 never more than 43nm. Hence my question about whether some ATOM stations are not receiving ADS-B In. Does any one else have PAW/SE2 comparison for their flights? And I recognise that this is air-to-ground, not air-to-air.

[exfirepro]

Hi Smaragd / Ian,

Not all ATOM Stations have 1090 Rx yet - including some which were upgraded from original OGN only - though most of the newer ones do and we are trying to encourage those that don't to add it. All it needs is a 1090MHz antenna, co-ax and an additional SDR.

Of the 8 stations listed above, I can see no evidence of 1090 ADSB or CAP1391 (SkyEcho) reception at either PWCalne or PWOxford. All the others listed are showing definite recent results for both ADSB and CAP1391.

Hope this helps.

Regards

Peter

[Smaragd]

Thanks Peter. I'll see how the picture fills up with a few more varied flights.

[Dave jones]

Hi Geoffrey
Just looking at your post. I seem to have a similar problem and set up too yours. I have a PAW Rosetta, recently installed SE2 and mode s Garmin 328. Good results with PAW but none ADSB. SE2 also not brilliant. My aeroplane is metal low wing (PA28). Hex code 401C1B. Check my vector pole results over 3 flights. Pete is helping me this problem under another thread.
Regards Dave