Hex codes starting with FF


#1

I’m using Piaware with Flightaware’s dump1090, and on port 10001 (the Flightaware output port), there are many entries that have FFxxxx as the aircraft hex code, where xxxx is also the squawk code. I also noticed that the altitude stays the same for a given hex code.

What are these entries? Are these actual aircraft or just noise/errors?


#2

I found out they were MODE A only and the system has a problem decoding them. But that is all Ive found out so far.

How ever I posted the same question on the PP Yahoo group and never got a true explanation. I could turn them off PP but I cannot on Dump 1090. I can get up to 30 of them. They drive me crazy sometimes.


#3

For dump1090, make sure you don’t have the flag --modeac.

In that case, does FlightAware use Mode A/C output in any way? Should we bother having that enabled?


#4

Mode A/C data only includes altitude or squawk data but no ICAO hex code. The radar requesting the ping knows what it has asked for but the rado transmission from the aircraft doesn’t indicate which info it is.


#5

In that case, it probably isn’t useful to capture the info, especially if dump1090 isn’t/can’t associate it with the actual hex code.


#6

I agree unless you can associate the squawk with a particular flight (by listening in to ATC) it isn’t much use.