Couple of newby questions

[Taildra99er]

Hello.  I've recently installed a Rosetta, using Skydemon as display.  Generally seems to be working well now that I have installed external antenna.  I made a flight on the w/e with a friend following close behind in a mode S equipped aircraft.  I saw him fairly consistently as a bearing less target, however the reported a/c registration seemed inconsistent.  Sometimes it reported correctly, but sometimes changed to an entirely different registration.  Pretty sure there was no other aircraft in the vicinity confusing the picture.  Why might that be then?  Secondly, why wouldn't I have received an M-LAT rebroadcast with derived position?  Our route saw us pass the ground station at Challock and this was displayed on my SD, so I'm assuming we were good to receive grid rebroadcast data.  I can see post flight, that FR24 successfully recorded an M-LAT track derived from my friends mode-S transmissions.  Lastly, if Rosetta is in receipt of both an M-LAT rebroadcast and a mode-s bearingless transmission, will it attempt to display both or is it clever enough to suppress the latter. 

Many thanks, great product.

[Admin]

Hello.  I've recently installed a Rosetta, using Skydemon as display.  Generally seems to be working well now that I have installed external antenna.  I made a flight on the w/e with a friend following close behind in a mode S equipped aircraft.  I saw him fairly consistently as a bearing less target, however the reported a/c registration seemed inconsistent. Sometimes it reported correctly, but sometimes changed to an entirely different registration. Pretty sure there was no other aircraft in the vicinity confusing the picture.  Why might that be then?

did it sometimes flip to C-xxxx ?
If so this is due to a Mode-C emission from the same transponder

Secondly, why wouldn't I have received an M-LAT rebroadcast with derived position? Our route saw us pass the ground station at Challock and this was displayed on my SD, so I'm assuming we were good to receive grid rebroadcast data. 

Was this feature enabled in your PilotAware Rosetta, it is off by default ?

I can see post flight, that FR24 successfully recorded an M-LAT track derived from my friends mode-S transmissions.  Lastly, if Rosetta is in receipt of both an M-LAT rebroadcast and a mode-s bearingless transmission, will it attempt to display both or is it clever enough to suppress the latter. 

Yes it will, if it matches the ICAO code both direct and from a ground station, then it suppresses the bearingless
if it loses MLAT, it reverts back to bearingless

Thx
Lee

[Taildra99er]

Many thanks Lee.

Did it flip to C-xxxx?

No it was G-something entirely different.  Guess I can check back in the flight log.  I'd noticed the same on a previous flight accompanied by the same aircraft too.

Was this feature enable..?

  I thought so, but it is a new toy!  Could you confirm where the switch is and I will check next time I'm at the aircraft.

Yes it will

- Very neat.

[exfirepro]

Hi Taildra99er,

The enabling switch for MLAT is on the PAW ‘Configure’ Setup Screen - accessed from 192.168.1.1 (it’s called Mode-S/3D).

To be sure what is going on, we need to check several settings including what Mode C/S Range you have selected, so can you post a screenshot of your Configure Settings please.

To get fixed position MLAT reports, as well as being in receipt of an uplink from a Ground Station yourself, the Mode-S aircraft must also be in range of at least 4 360Radar receiving stations in order for it’s position to be triangulated. There are a considerable number of these across the UK, many of which are not PAW ATOM-GRID rebroadcast stations. Where this is not happening, PAW automatically reverts to reporting the aircraft as a Bearingless target - with in your case SD’s coloured rings to indicate degree of risk, plus relative altitude and either Mode-S Reg or a Mode-C identifier.

The warnings you then receive are dependent on the Mode C/S Range and Vertical Separation you have selected in PAW Configure. In this case, Rosetta will inform you of the aircraft it deems to be the greatest risk but this can cause the system to alternate between reports from two aircraft with similar received signals, where for example one is much higher power (e.g. commercial) but at greater range than the other, and possibly still out of visible range. I suspect this was what was happening in your case.

Regards

Peter