Is it possible to properly receive mode A/C?

is it possible to properly receive mode A/C?

I use ver.7.2. downloaded from GitHub - flightaware/dump1090: Dump1090 is a simple Mode S decoder for RTLSDR devices, I can observe flights from 220 nm. I have got mlat.
Lately I witnessed a conversation between a flight controller with a pilot. The conversation went something like this:
Controller: Unfortunately I do not see you within a radar.
Pilot: Hmm, a colleague turned on only mode a. We are going to change it now.
Controller: OK, I see you now.
Pilot: Super, now we are on c mode.

In both cases I didn’t see this plane in the table. What steps could I take take to help with it?


You need to have mode A/C decoding enabled in dump1090 (–modeac switch), however the information it provides to a casual observer is limited. You can see that there is an aircraft squawking a particular code, or that there is an aircraft at a particular altitude, but you can’t really relate the two very easily since neither protocols have ID transmissions associated with them. This isn’t a problem for ATC, since the transmissions are in response to an interrogation which is directional from the radar head. In addition, mode A/C has no error correction so there will be quite a lot of errors and spurious data seen.

If you want to do more with mode A/C messages, you could have a look at something like planeplotter which has some kind of mlat system for them, but I have no idea how effective it is.


I have heard about planeplotter, but I guess it’s not available for RaspberryPi.
PiAware - Advanced Configuration Settings - FlightAware - I have found settings for A/C mode here, but my file has less options:
Where exactly should I be looking for “allow-modeac” option? Majority of commands just do not show in my location.

sudo nano /etc/piaware.conf

allow-modeac yes

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Besides receiving those AC “answers”, you would have to be synchronized with the ATC rotating radar position and know what interrogation ID code they have sent out.
It’s really not used anymore, except some military flights, not sure in what part of the world are you (and why are you interested).

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He’s in Belarus, so probably interested in military flight over Ukraine.

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Most likely - Poland and Lithuania. No military aircraft over Ukraine uses ads-b


The conversation quoted in the first post wasn’t about any kind of military aircraft, but was from a Cessna in training. If it was being used by army, that would just be an addition to that.

I didn’t manage to edit the line that geckoVN sent, but I can see in logs something about A/C:



I’ve found a description of planeplotter for rasberrypi but have not tried it out yet: | Updated ppup1090 - supporting Mode A/C MLAT