Not seeing mode C aircraft on Sky Demon

[Rogerpenney]

I have had an issue with my ADSB aerial which is now repaired and I can see on traffic logging that the unit is receiving mode C aircraft as well as mode S.
When  I connect to Sky Demon I am only seeing mode S aircraft. I have read all the setup instructions over and over, I think I am set up correctly, has anybody got any ideas please?
Thanks,
despirate of Wirral!

[Admin]

Hi Roger

This may sound a silly question, but bear with me so I know we have a common understanding

what symbols are you expecting to see on SkyDemon to represent
Mode S
Mode C

And under what circumstances do you expect them to be shown ?

Thx
Lee

[Ian Melville]

You have set SkyDemon to show bearingless targets?

[Rogerpenney]

I have got Demon set to show bearingless targets.

I am  comparing what I see on demon with flightradar24 whilst on the ground just one mile south of Wal VOR and I see all the commercial stuff Easy, Ryanair etc as a jet symbol. I do see odd light aircraft which looks like they are on mode S, usually Cirrus and better equipped types,  the vast majority of light aircraft many of which I know to be on mode C are not seen. I have the unit outside with a clear view of the Sky etc.
Yesterday there were 5 light aircraft just north of me not seen, even one passed overhead coming into Liverpool and I know he was on 5050 mode C, nothing showed up on Demon connected to PAW.
I can see commercial stuff way beyond the Isle of Man no problem.
The other day we met a helicopter near Banbury at 1500’, he was squalking 7000 mode C  and I didnt see him on Demon. Nor am I picking up gliders on Flarm.
Basically I do not see the main dangers to me, other light aircraft unless they have PAW and gliders.

[Admin]

Hi Roger

I think there is confusion regarding what is a bearingless target
Can I ask you watch this video, and then lets revisit your question

https://youtu.be/jUaxbGnfZX0
Thx
Lee

[Rogerpenney]

Thanks, viewed. I am not seeing any symbols for mode C and S. I dont use audio as Liverpool is so busy where I am based.
The unit is receiving mode C and S as I can  see them in the traffic log when I view the unit via iPad.

[Admin]

Hi Roger,

Ok, we are on the same page - that is good.
As you have said, the traffic table will list all of the Bearingless Mode-S and Mode-C contacts it receives
This does not necessarily mean it is passed to the Navigation tool for display.
In order to be passed there are 2 criteria, which are controlled by settings in PilotAware, and BOTH must be met

1. relative height
The height difference must be within these bounds, so if you have set the bounds to be +/-2000ft, and an A/C appears 2100ft above you - it is ignored. If it is 1900ft above you - it is considered

2. range (long, medium, short)
This is a test of the signal strength monitor, using a machine learning heuristic algorithm
This analyzes data nd determines the range into the categories of long/medium/short
If you select long, it increases sensitivity and will display A/C which are further away than when short is selected

So for a 'wide open test' you may want to select the largest value for relative height, and long range.

Finally, there are 2 other additional factors to consider

3. Antenna location
The position of your own antenna will have an effect on the reception quality, and hence judgement of the threat calculation. Wherever possible, let it have a clear view of the sky. Although as traffic approaches close, your antenna location has less of a degrading impact due to the inverse square law.
https://en.wikipedia.org/wiki/Inverse-square_law

4. Transponder Interrogation
Finally, an aircraft transponder will only emit Mode-C and Mode-S responses, when interrogated by ground RADAR.
in which case, dont expect aircraft either on or close to the ground to provide any Mode-C or Mode-S responses at all, this will likely only ever happen when airborne, and for sure only when within range/reception of a gound RADAR interrogation

A couple more words on the subject.
- what version of PilotAware are you running ?

- you can gauge the threat of the A/C by the "Sig" column in the traffic table, additionally the traffic table is color coded, so if a Mode-C or Mode-S row in the table gets highlighted Green/Amber/Red - this is an indication of meeting the threat criteria described above, and that a warning has been sent to the Navigation tool, which should elicit a display symbol

I hope that helps

Thx
Lee

[Rogerpenney]

I bough my unit last year at the Shawbury safety day and am running the latest 2018 software.

Will reset parameters and see how that helps

Thanks for your help Lee.

Roger.

[Skrswift]

I am also having issues seeing aircraft.

I see the odd light aircraft, and easyjet, british airways etc, but i am not seeing most planes with their transponders on.

My friend was flying next to me Sunday with his transponder on, i could see him find on FlightRadar24, but not on Pilot Aware.

Same for a cessna caravan that flew past me, he was on FlightRadar 24, but not on PilotAware.

I have upgraded my Raspberry Pi to the recommended B Pi2.

Could i have a setting wrong?

Kind regards

Kiran

[Ian Melville]

Hi Kiran,
Can you post screenshots of your home and config pages please?

[Admin]

Hi Kiran

In addition to Ians request, please also post the traffic page, and importantly, please do this from outdoors so that we get a good view of what is being received.

As a final note, are you aware that FilghtRadar24 displays
- Mode-S (via MLAT)
- OGN (flarm, OGN Trackers, PilotAware)
- ADS-B

So When you say your friend had his transponder on, can you tell us what type of transponder ?

Thx
Lee

[tonys]

ref point 4 by admin
quote
4. Transponder Interrogation
Finally, an aircraft transponder will only emit Mode-C and Mode-S responses, when interrogated by ground RADAR.
in which case, dont expect aircraft either on or close to the ground to provide any Mode-C or Mode-S responses at all, this will likely only ever happen when airborne, and for sure only when within range/reception of a gound RADAR interrogation

so from above statement transponder equipped aircraft cant be see in paw
if   a/close to the ground
     b/in area not covered by radar

is that correct ?

[Admin]

so from above statement transponder equipped aircraft cant be see in paw
if   a/close to the ground
     b/in area not covered by radar

is that correct ?

yes, this is correct
Thx
Lee

[Skrswift]

Hi

Thank you for the reply’s.

I’ll go to the airfield tomorrow and get screenshots.

My friend has a Trig 21, on Sunday he was Mode S.

I still don’t fully understand how transponders work, but if it shows up on FlightRadar24, should it also show on PAW? There must be a radar for the flightradar24 to work?

Kind regards

Kiran

[Admin]

Hi Kiran
The only systems supporting GPS position information
are ADSB, Flarm, Pilotaware

All others require RADAR or Multilateration

Kiran, can I recommend you watch the pilotaware videos on YouTube, there is a complete description of what you need to know

Thx
Lee