I don't see why you couldn't use it, but i doubt it would solve the problem. Are you sure moisture is the issue? When dealing with outdoor networking, there are a whole host of porblems that can arise from surrounding interference, including cell/portable phones. The further the distance the signal needs to travel the more likely these factors are the answer.
Besides the point, moisture is not good for electronics, especially the ones which have power flowing in them. I would suggest a permanent remedy for this 'moisture' issue. By either a temperature controlled area, or using a satalite dish method, as they are not affected by the elements as easily.
(i've never actually tried the latter, but i know it can work)