Try lamping from a farm yard out to the field behind lights on the farm that the fox is used to as if you have fox it would have been round the farm and wont suspect you it would just think its another light as long as your quiet enough, and theres some really good sqeekers on the market, my mate does them for £2 one that you put in your mouth just the size of half a ten pence, if you go on pigeon forum his name is-- acton pest control