A few days ago I put up a 1090 MHz antenna to use instead of continuing to use my two meter J-pole for PiAware. Since then I’ve noticed every once in a while I’ll pick up a bunch of planes sitting on the ground at the airport just over twenty miles away. They’re there for a few minutes, then they disappear. Is this normal behavior?
I tried searching here but just kept getting results about electrical grounding and ground planes!
Could be TIS-B … that often turns on and off.
If you’re actually receiving the planes themselves then it’s just intermittent reception.
I think that’s it. Hopefully I’ll get better search results for TIS-B. I hadn’t thought about the color they were showing!
Hi,
Yes, they are definitely TIS-B and the pseudo hex code starting with 2F4 matches the Detroit Metro Wayne County Surface Area as expected.
2f4 or 2F4 = Detroit Metro Wayne County Surface Area
If you see inflight TIS-B is will probably be as below for your area.
2b4 or 2B4 = Cleveland Center
When you do your online reading about TIS-B, make sure you also look at ADS-R. ADS-R is related, but will display actual hex codes since the aircraft identification is known.
-Dan
Yep, it’s TIS-B. To explain the behaviour:
TIS-B is transmitted only when there is a nearby ADS-B-in-equipped aircraft; this is why it’s only sometimes visible
TIS-B is transmitted from ground-based antennas that aren’t necessarily located at the airport, so you may be able to receive data from a TIS-B antenna even if you wouldn’t be able to hear signals from the aircraft’s location directly.
The clusters-of-ghost-targets-on-the-ground is very typical of TIS-B data. I think the source data is something like surface primary radar (or perhaps Mode C?), and the logic to combine the raw radar returns into useful tracks on the FAA side doesn’t seem all that great.
We see similar behavior in the direct ASDE-X-derived feeds, yes. ASDE-X combines data from multiple sources so it’s not immediately clear exactly what source is causing the ghosts.
