Originally Posted by
Lead Balloon
I built one of the Stratux ones. Amazing thing is how many (even high level RPT aircraft) you can spot visually, with the aid of the output of the unit displayed on the EFB screen. None of those high level aircraft is a collision risk - very ‘high’ while us nobodies are very ‘low’ - but it does demonstrate that the unit picks up and provides pretty accurate information about aircraft putting out Mode C data.
But the ‘blindspot’ is that it requires ‘something’ to be interrogating the other aircraft’s transponder….
ADS-B Out position messages are/ought to be transmitted once-per second, no interrogation required. I don't know about message collision avoidance in ADS-B, but I am aware that potential saturation of the time available for messages is supposed to be the reason that it was specifically banned for use from unmanned aircraft, aka drones/remote control aircraft. What happens with other radar/communication systems that also integrate ADS-B data is something else, but all on it's own there is no interrogation required.
This may be better explanation:
https://www.icao.int/meetings/amc/ma...sitf4/sp01.pdf