Dalek
<<Portable DME, Intrinsically reliable?
Are you stating fact or is that a wild stab in the dark?>>
From a systems view, it was like plugging a GPS into the cigarette lighter socket in your car - if what you got made sense and was of the right order then it was, from what I've heard and would expect, more accurate than radar.
But why ask me? - there must be those around who have used it - try persuading them to make a comment on the open forum - good luck!