Mobile

This is a word whose use and meaning have been changed by developments in technology, and a consequent slippage in ordinary usage.

The original use of mobile was as an adjective meaning ‘moveable’, capable of being moved. (The word automobile simply means ‘that which can move on its own’, i.e. without the help of animals such as horses.) So the word was happily applied to a telephone that did not need to be connected by wire to a socket or wire in a building. You could take a mobile telephone with you in a car, on the street, or in a train. Naturally enough, the term mobile telephone has been abbreviated in colloquial usage to mobile. So now we have oxymorons like ‘a mobile mast’ – which stays exactly where it is built, and does not move at all. The mast is not mobile – it is static.

If you want to write fussily correct academic English, say a mast for mobile telephones (or telephony), or a telecommunications mast or some other more careful and exact phrase. Otherwise, call it a mobile mast like everyone else. Certainly do this if your reader can be expected to use this terminology.