I'm investigating the possible application of mode 3AC interrogators in EU airspace.
My experience is unfortunately limited to North America, and I'm unfamiliar with Mode S systems / function.
All the information I've managed to find describes mode S trabsponders as "backwards compatible" but fail to go into detail.
Is the backwards compatibility seamless and simultaneous?, Able to reply to both mode S and mode 3 interrogators in real time? Or a toggle switch between modes, in which when mode S is selected mode 3 interrogations will be ignored?
Do European standards allow mode 3A/C interrogators to operate within their airspace? Could this cause interference with local mode S infrastructure?
Are there any other potential concerns with operating a mode 3 interrogator in EU airspace?
To clarify I am speaking from the perspective of a ground station. As in using a mode 3AC SSR on an airport in EU airspace.
Any information would be greatly appreciated, thank you.