Originally Posted by
Jan Olieslagers
That's not up to logic. I agree with @tescoapp so far: if this MLAT stuff is to work, every plane needs to carry an active transponder (though I don't understand from the given text it needs to be mode S, but that's a side-point). So a TMZ would in fact be required to make it really waterproof. Otherwise, it will never offer more than suggestions.
This test does not require a transponder. It can be a much less expensive Sky Echo, Flarm or perhaps others. The test equipment is supplied by Uavionix, the suppliers of Sky Echo.
Sky Echo is ADSB so needs only to be picked up by one receiver unlike mode S which requires 3 for multilateration.