ICAO ID FFxxxx

[n5pwp]

I'm using Dump1090 to feed Virtual Radar Server and I keep Dump1090's interactive window up to correlate what it sees and what's displayed on the VRS display. I've stumbled across this a few times now and am wondering what's going on. I've tried doing some Googling on it and have come up empty-handed. My question is what are the ICAO hex id FFxxxx? The x = hex digits. In my example here you can see FF2171, FF7722 and FF3070 and so on. The digits seem to correlate to the squawk id. But I have FF1010 at 30300 ft altitude and one FF0010 is at -800 ft altitude. What are these things? None of them show on VRS. Maybe because They're Mode A? None of the registries I've found have any info on them. Is this just Dump1090 acting weird? They come and go like any other a/c I've seen.

The system I'm receiving this on is an RTL8238 dongle being fed by a scanner discone going to a FlightAware 1090 bandpass filter.

 

[BM82557]

Looks like Mode A does use a 4 digit id - https://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes

I did find this on what you are seeing with Dump1090 - Hex codes starting with FF : ADS-B Flight Tracking

 

[n5pwp]

Thanks BM82557

I stumbled across the 1st link in your post and have bookmarked it. the 2nd link was kind of anti-climactic. I do switch back and forth between using the --modeac switch in Dump1090 because I had read that it helped with MLAT data. I am a feeder for ADSB-Exchange and they provide MLAT info for my VRS display. Unfortunately they feed EVERYTHING to you and tracking 6-7000 aircraft can get kind of straining on the oil bandwidth budget for the month. It would be nice if they could have regional feeds and you could get just your general area's data. With the MLAT data I can see the stuff that doesn't use ADSB and provide coordinates for plotting on the map. Thanks for the reply. I don't know how I missed the PP link you provided but I guess its all in the keywords you use in Google. I guess I need ot turn off modeac.

Mike

Did some more searching and found this:
http://http://aviation.stackexchange.com/questions/11300/what-kind-of-ads-b-identification-code-is-ffxxxx-where-xxxx-are-numbers-i-e-ff