We have just started to use the water 'scarecrow' - sets of a jet of water in small fast squirts when sense movement/heat. So far so good. You'd have to be ok with having your deck watered - the idea is eventually the fox will just stay away because it knows it'll get sprayed otherwise.
Would a fox do a smelly wee on the doormat outside our back door? I keep smelling something funky and today I noticed a dark stain... even as I'm typing this, I think I know the answer. Eww. How to deter this?