Mode C readsb or dump1090-fa output on Port 30003

I would like to record Mode C transponder responses from nearby aircraft and filter the results by altitude and signal strength to detect nearby low and approaching flights (older GA aircraft in rural areas, for instance). As noted in the Saving Mode-AC post, the --modeac works for an instance of view1090 or readsb running from the command line and writing on stdout. However, this configuration option does not seem to affect the output on Port 30003. I have considered using the --beast-modeac option or modifying the source code of the decoder/demodulator. I am not familiar enough with either of these options to have a sense of how feasible they are. (I am not familiar with the code or with using the Beast output). Any ideas, recommendations, or workarounds?

I have to respond by email since my browser is “unsupported”. Hope it’ll

I run a modified “view1090 --modeac” in a “screen”-session (tmux might
work, too).

The modification writes modeac-data every 10 seconds into a relational
database (PostgreSQL). Not exactly wthat you want, ugly and not-portable

  • but works for me.

— dump1090.h.orig 2019-06-19 23:08:02.000000000 +0200
+++ dump1090.h 2019-06-20 14:52:18.000000000 +0200
@@ -246,7 +246,7 @@
// at least greater than a given level for us to dump the signal.

-#define MODES_INTERACTIVE_REFRESH_TIME 250 // Milliseconds
+#define MODES_INTERACTIVE_REFRESH_TIME 10000 // Milliseconds
#define MODES_INTERACTIVE_DISPLAY_TTL 60000 // Delete from display after 60 seconds

#define MODES_NET_HEARTBEAT_INTERVAL 60000 // milliseconds
— interactive.c.orig 2019-06-19 23:08:59.000000000 +0200
+++ interactive.c 2020-03-21 12:55:53.297913286 +0100
@@ -51,6 +51,8 @@

#include <curses.h>

+#include “/usr/include/postgresql/libpq-fe.h”

Thank you for sharing your workaround! I’ll give this a try. As you noted, I’d ideally like to get it working over network output, but I’ll make do with my current (very limited) understanding of how it all works. If I eventually figure out the network approach, I’ll share it back.

Thanks :slight_smile:

The 30003 output format is very constrained and doesn’t (can’t) contain many things, including A/C output. You’re better off consuming from port 30005.

This is good to know. I think it is time for me to dive in and learn the protocol.Thank you!

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