How do I stop neighborhood male cat from spraying?

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I have a dilemma. There is a male cat in the neighborhood and he comes to my house to spray. Yes, I have a female cat outside that is not fixed but there has to be a way to stop him from spraying on my porch. He did this before we got this female cat when I had a female cat indoors but she is fixed. I don't know if he can smell her even though she doesn't go outside or what. But now I have an unfixed female outside and his spray can be smelled throughout my house without opening doors or windows. The smell is making me sick and giving me a migraine. Other than getting her fixed (because that is taking longer than I thought) what can I do to discourage him from spraying on my porch? I have sprayed vinegar but that doesn't seem to bother him. Any ideas???