Hi,
I was wondering, is MODE-S traffic sending data even when not interrogated on 1030 MHz?
i.e Is Areo Tracker only picking up MODE-S traffic if it has been interrogated by an other source?
Regards,
JJ
I believe Mode S data is only sent by the transponder when it is being interrogated by SSR radar or TCAS equipped aircraft.
From Wikipedia:
Mode S features
“Upon interrogation, Mode S transponders transmit information about the aircraft to the SSR system, to TCAS receivers on board aircraft and to the ADS-B SSR system. This information includes the call sign of the aircraft and/or the aircraft’s permanent ICAO 24-bit address (which is represented for human interface purposes as six hexadecimal characters.) One of the hidden 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.”
Yeah, that was what I gathered as well. So we only see Mode-S on the Aero Tracker if the target has been interrogated by a SSR (Usually at an airport I assume). The rest of the time it is quiet.
During my use of my Tracker it has never been an issue. Maybe you won’t detect Mode S only transmissions if the aircraft is on the ground at a non-radar equipped airfield, or flying at very low level, so not picking up any radar interrogation. Otherwise the aircraft position should be MLAT determined and you receive its location via the Tracker’s LTE mobile data connection.