Mr Jabawocky and Busdiver
Thank you for confirming my limited understandings.
It seems then that these portable devices are only of value to the owner where monopulse radar or TCAS monopulse emulation exists.
This is still beneficial but really only value in radar airspace or against the big TCAS equiped aircraft, not for other GA or RA Aus aircraft on potential course of collision.
To myself I think my read of ADS-B is meritorious in comparison as it works from/to all equipped aircraft (as long as is 1090ES, as I read there is extreme omplication in USA plans for mixed system of 1090ES and UAT).
This debate is very informative to researchers.