CommissarVulpinThis building built in the 60s has a sign warning you that there's a microwave
Older pacemakers could be adversely impacted if people who had them were anywhere near a running microwave oven - we had those signs up around the office kitchenette less than 15 years ago.
Could also be a radio research site, but I doubt OP wouldn’t know that’s where they are. If the equipment is sensitive enough to be effected by a retail microwave, they’re already in a valley way outside of any town.
Green Bank?
I wasn’t thinking of any in particular, but that’s one of them. I remember an old story about how some lab couldn’t get any good signals around the same time every day. They were chasing bugs for months before realizing that someone brought in a microwave and was heating their food on break with it. Labs like that normally only allow toaster ovens and such.