2 things to tell new users

[neilmurg]

If PAw reports 100' below, target may be above or below, there's a 200' allowance in altitude reporting (so technically could be 400' out, but 200' in my experience)
If you're climbing or descending and get a 'Danger 200' above/below' without a 'Traffic' or 'Warning' before hand - it's YOUR Mode S/C it's seeing, don't sacrifice aircraft control looking for it (I'm not saying don't check)

Get used to the traffic reports on the ground and in the circuit, use it to build your SA (situational awareness) and familiarity with what the system is telling you

[exfirepro]

Neil,

What PilotAware software version are you running?

Not sure what you mean by..’there’s a 200’ allowance in altitude reporting’. If you mean from the transponder, Mode C transmits altitude in 100ft steps - correct, but with Mode S / Mode S-ES, the accuracy is within +/- 25 feet.

The problem of PilotAware detecting your own transponder during rapid climb or descent was sorted a while back, so you shouldn’t be getting this type of alert if running the latest 20180520 software unless one of your devices is running the wrong Hex Code.

Regards

Peter

[Paul_Sengupta]

The tolerance from the altitude encoder via the transponder to ATC radar is assumed to be within + or - 200ft...i.e. ATC will assume that there may be an error in your transmission of up to 200ft from actual altitude.

[neilmurg]

The tolerance from the altitude encoder via the transponder to ATC radar is assumed to be within + or - 200ft

Yes Paul, so when I'm taxying and get an alert for an aircraft 100' below, I tend not to look down :-$
PAw version 20180520, and yes I still get those alerts when climbing, Garmin GTX330 (not ES) I'll recheck the Hex's...

[neilmurg]

PAw Hex checked OK, and Farnborough West call me by the right name when I'm on listening Squawk (Couldn't get the 330 to display Hex, unfamiliar)

[Ian Melville]

If you change you PAW HEX to something else, temporary, then your PAW will list your aircraft as a thret, and list it in the traffic table. You can read the transponder hex code in there.

[neilmurg]

thanks

[Seanhump]

Powering up the GTX330 whilst holding the FUNC key gets you to the config menus .. here you can easily view your Hex ID set in the transponder

I'll dig out the instructions later if you like..?

[neilmurg]

Powering up the GTX330 whilst holding the FUNC key gets you to the config menus .. here you can easily view your Hex ID set in the transponder

Thanks Sean, that's great. I have the manual, but ran out of time after I'd tried pressing the FUNC key 27 times and it refused to understand me.......

[T67M]

Not sure what you mean by..’there’s a 200’ allowance in altitude reporting’. If you mean from the transponder, Mode C transmits altitude in 100ft steps - correct, but with Mode S / Mode S-ES, the accuracy is within +/- 25 feet.

Mode S/S-ES can carry altitude data with a RESOLUTION of 25ft, but the ACCURACY is determined by the encoder and is only +/-200ft, and the RESOLUTION and PRECISION of most GA encoders is 100ft. Just changing the transponder to a Mode-S unit doesn't magically improve the accuracy of the system as a whole.

[GeoffreyC]

Mode S/S-ES can carry altitude data with a RESOLUTION of 25ft, but the ACCURACY is determined by the encoder and is only +/-200ft, and the RESOLUTION and PRECISION of most GA encoders is 100ft. Just changing the transponder to a Mode-S unit doesn't magically improve the accuracy of the system as a whole.

Agreed.  When I first fitted my Trig TT21 and with Luton ATC checked the calibration to my altimeter and GPS,  it was over-reading by about 130 feet (and the altitude is rounded up to the nearest 100' making the worst case 200' off).    Speaking to Trig they said that that was within allowable tolerance but they sent me a replacement encoder head (the bit that goes on the dashboard),  this one was more accurate (80' out I think) so I've continued using it.

Be aware of this when flying under controlled airspace.  I try to fly at least 300' below to ensure that I don't worry ATC with false alerts.

[Admin]

Agreed.  When I first fitted my Trig TT21 and with Luton ATC checked the calibration to my altimeter and GPS,  it was over-reading by about 130 feet (and the altitude is rounded up to the nearest 100' making the worst case 200' off).    Speaking to Trig they said that that was within allowable tolerance but they sent me a replacement encoder head (the bit that goes on the dashboard),  this one was more accurate (80' out I think) so I've continued using it.

Is that true ?
It seems crazy to always round up, especially if the step size is 100'
it would seem far more sensible to 'round to nearest'
Thx
Lee

[GeoffreyC]

Is that true ?
It seems crazy to always round up, especially if the step size is 100'
it would seem far more sensible to 'round to nearest'
Thx
Lee

I agree Lee,  but I'm pretty sure that that was the calibration experience I had with my Trig.  I can remember a number of climbing and descending tests, comparing my Trig to my GPS and my altimeter to see how well the Trig altitude displayed matched. 

Maybe I'll go and try it again to confirm.

Geoffrey