Author Topic: Ghosting  (Read 1159 times)

malcolmR

Ghosting
« on: June 06, 2024, 09:22:34 pm »
I installed external aerials on my champ over the winter and have adsp out on my transponder using the paw gps. Since then  I have been plagued with what I assume is ghosting. I did not have this with internal aerials.   I get multiple danger warnings/red circles  giving heights above and below in rapid succession.  Warning frequency seems to drop/disappear when am remote from airfields/strips  and I am wondering whether it is assocaited with proximity to atom stations.  I am as sure as can be my device is configured correctly and have only one a/c on my skydemon.  Any advice or suggested investigations welcome.

Malcolm Rogan
G-DHAH

PaulSS

Re: Ghosting
« Reply #1 on: June 06, 2024, 11:00:41 pm »
HEX codes have been known to change themselves, especially with an update etc. I would double-check your HEX code is correct in the configuration page.

What transponder are you feeding for ADSB Out?

malcolmR

Re: Ghosting
« Reply #2 on: June 08, 2024, 08:05:02 am »
trig transponder.  vector output shows paw has correct hex code

PaulSS

Re: Ghosting
« Reply #3 on: June 08, 2024, 11:13:03 am »
I would still check the config page to make sure it is right.....it only takes 5 seconds.

You haven't got SafeSky running in the background on a phone or similar have you? I've seen that spew up contacts and it took ages to track down the problem. It wasn't until the owner said he'd just check something on SafeSky and took his phone from his rucksack that the penny dropped  :D

steveu

Re: Ghosting
« Reply #4 on: June 08, 2024, 07:29:01 pm »
I would still check the config page to make sure it is right.....it only takes 5 seconds.

You haven't got SafeSky running in the background on a phone or similar have you? I've seen that spew up contacts and it took ages to track down the problem. It wasn't until the owner said he'd just check something on SafeSky and took his phone from his rucksack that the penny dropped  :D

These are the top two reasons for me so I would endorse this solution.

Admin

Re: Ghosting
« Reply #5 on: June 09, 2024, 01:43:39 pm »
If you have adsb out, you should see two emitters on vector, is this the Case ?

malcolmR

Re: Ghosting
« Reply #6 on: June 16, 2024, 07:40:39 pm »

Yes - looks good coverage from both.

Haven't had chance to check hex code on device but I assume coverage from vector shows this correct.  Will do so this week.

Beginning to think I really had multiple a/c above and below within 500 ft and seeing none which is rather alarming!

exfirepro

Re: Ghosting
« Reply #7 on: July 03, 2024, 04:58:44 pm »
Hi Malcolm,

You certainly should check that you have the same (correct) ICAO Hex for your aircraft in each device you are using. Although rare, it isn't unknown  for the HexID in PAW to revert to the default 'MAC-based' HexID. I have however also found the wrong code in transponders on several occasions.

That said, multiple Red Circle 'Danger' warnings can only be generated from Mode-C or Mod-S equipped aircraft - which can include high power responses from CAT aircraft on the ground at major airports to ground radar interrogations. This would be consistent with your report. These can be picked up and reported at a fair distance from the airfield (they usually appear suddenly as a 'Red' 'Danger' warning without going through the preliminary 'Green' and 'Amber' stages. If this is what you are seeing, try reducing the Bearingless Traffic reporting range in your PAW Configure Screen, and also consider restricting your selected relative altitude reporting level as well. (Don't forget to 'Save' the changes before exiting the Configure Screen).

The other issue that can cause 'rogue alerts' is close proximity between your transponder and PAW 1090 Receive antennas, which has been known to overload the front end of the 1090 SDR, though I know Lee did a lot of work in previous software versions to try to eliminate this issue. How far apart are these two antennas on your aircraft?

Let us know what you find and whether these suggested changes resolve the issue for you.

Regards

Peter