"David Hare-Scott" wrote in
:

It's just as well I wasn't suggesting that isn't it. The owner
might be persuaded to keep it at home, some do as a matter of
course. The owner might not know it wanders and be mortified that
it causes problems. The owner might not give a toss either but
until you ask you don't know.

or it could very well not *have* an owner. there are thousands of feral
cats in the US. there are lots of brain-dead morons that get cute
kittens, keep them for a few months & then dump the un-neutered
(because it costs money & it's "just a cat") animal out in the country
somewhere because it's no longer a cute little kitten, go back to the
pet store & get another cute kitten.
to the OP, a motion activated sprinkler should help with your problem.
there's no such thing as an ultrasonic animal deterrent (well, not one
that actually deters any animal. there's are plenty of places that will
happily take your money for something that doesn't do anything))