Ok, the item in question is 8 month old, and its a digital TV adapter for a Mac, from eyeTV.
Bought from Amazon.
The dongle is thumbnail sized, and after 8 months, the weight of a coax plugged into it has snapped the internal aerial connection.
Its all sub micro stuff and well beyond my ability to resolder - the pad has come off the board.
Elgato say 'contact who you bought it from' but amazon has no button to click for 'it broke after 8 months of normal use plugged in the back of a floor standing mac, its crap'
and of course who knows where the packaging has gone.
Have I just basically been ripped off?