Mode-S Callsign

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nzradar
Posts: 20
Joined: Wed Nov 07, 2012 4:42 am
Location: New Zealand

Mode-S Callsign

Post by nzradar » Wed Jun 03, 2015 9:04 am

I notice an asterisk next to the callsign on those flights having no positions and I understand this means that the callsign extracted from the message may be incorrect, however, I'd like to know why this callsign, right or wrong, isn't included in the Basestation (aka 30003) format.
Michael
New Zealand
Flightaware Flightfeeder System/VRS

agw
Posts: 2241
Joined: Fri Feb 17, 2012 3:20 am

Re: Mode-S Callsign

Post by agw » Sat Jun 06, 2015 3:14 pm

I've just had a look at the code and there's nothing in there to stop suspect callsigns from being shown on a port 30003 feed. To test this I've connected to a VRS port 30003 rebroadcast server using Chrome and then searched the output for a callsign that is marked as possibly incorrect on the site. The site is showing an Air Hamburg flight with a callsign of AHO325C* and that callsign does appear in the feed from the rebroadcast server:

Code: Select all

MSG,5,0,0,3CCB20,0,2015/06/06,15:09:31.077,2015/06/06,15:09:31.077,AHO325C,13700,,,,,,,0,,0,0

nzradar
Posts: 20
Joined: Wed Nov 07, 2012 4:42 am
Location: New Zealand

Re: Mode-S Callsign

Post by nzradar » Wed Jun 10, 2015 9:56 am

Oki doki, I've taken the 30003 output direct from the FR24 receiver and also from ModeSMixer2 port 30003 having first fed MSM2 with port 30334 data from the FR24 receiver. I think that the FR24 receiver is sending the suspect callsign on 30334 as I see them in VRS but I've yet to look at the VRS re-broadcast data on 30003 so I'll check that. Thanks for the advice. ;)
Michael
New Zealand
Flightaware Flightfeeder System/VRS

agw
Posts: 2241
Joined: Fri Feb 17, 2012 3:20 am

Re: Mode-S Callsign

Post by agw » Sun Jun 14, 2015 3:35 pm

Ah right - I think the reason why they might not be appearing on the FR24 box and ModeSMixer2's port 30003 feed is because the callsign isn't being taken from one of the Mode-S or ADS-B messages that usually carry the callsign. It's being taken from one of the other messages. I can't remember the details now, I know it's taking it from a message that's carrying the BDS 2,0 register but there's something about that message which means that you can't always tell that it's BDS 2,0 and not something else. Anyway it's unreliable, which is why a lot of things don't bother with it and why VRS marks callsigns taken from it with an asterisk.

If you want everything to be consistent then you can tell VRS not to bother trying to detect BDS 2,0 messages - the option is in Tools | Options | Raw Feed Decoding | Ignore callsigns from BDS2,0 messages.

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