In article ,
Ron Natalie wrote:

Actually, the apostrophe is NOT incorrect here if you consider VOR
to be a grouping of letters (abbreviation) rather than a acronym
(a word made out of the abbreviation). Certainly DME is not an
acronym. The rules of usage allow don't really favor one or the
other.

???

VOR and DME are both acronyms (VOR being a compound
acronym).

VOR - Very High Frequency Omni-directional Range
DME - Distance Measuring Equipment

--
Bob Noel
Looking for a sig the
lawyers will hate