Those data have no position and you don’t know which aircraft it is either.
I’m not sure there are even any aircraft left operating Mode A/C only transponders in Germany.
To give an actual answer:
Have you check the basestation output via TCP?
You could do this:
nc localhost 30003 > lots_of_data.txt
Not sure how that would be useful, but the data is saved.
I’m pretty sure most of the Mode A/C aircraft you see are actually just messages from ModeS transponders which are usually ignored.
One of the features of Mode S transponders is that they are backwards compatible; an aircraft equipped with a Mode S transponder can still be used to send replies to Mode A or C interrogations. This feature can be activated by a specific type of interrogation sequence called inter-mode.(https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)* ]
@obj Do you know if any radars are still interrogating Mode A/C?
I suppose they are, otherwise the message rate shouldn’t go up when switching to --modeac but it does.