Even when you build the first one, theres hundreds of thousands of expected hours of testing before you even had control over which timeline and what time period you're going to jump to. And no invention in history is ever done in only one place, at the very least you have the same invention in 2-3 places at the same time.
And lets say you even did know the math and frequencies to use it properly, chances are you're not going to be telling people, so why would you assume you could find someone else doing the same thing? If other people had one, you are not likely ever to come across them.
Why also would you want to destroy the other one?