Andrewgr2: The UAV needs to have a Flarm device which sends its position and receives similar position messages from any Flarm equipped around. This is how it can display the possible threats to you. So highly recommend you install one, if flying in airspace with these creatures, although it is not required in anywhere. Even better, make it a PowerFlarm and you also get ADSB In and see more targets.
Surely without anything installed, the UAV cannot been seen with anything else than a primary radar (if large enough) or an eye (if close enough). I thought that was self-evident.