Station ID is every hour. Also you have to say it in a very specific format: Call letters, city; or call letters, frequency, city. No additional words in between: “WKRP in Cincinnati” would be invalid.
TV stations are allowed to do it visually. When I was young it was common to see it as a full screen ID in between shows (often with a quick weather report, “time and temperature”). Later most stations I saw quit that and just put it as a bug at the bottom of the screen over top of the show.
Including your frequency is especially effective for customer retention - I still remember the MW frequency of one of my favorite radio stations from my youth because it was included in the name, even though I listened to it via satellite ("Virgin 1215" - apparently it's called Absolute Radio now, and medium wave transmissions were discontinued on 20 January 2023: https://en.wikipedia.org/wiki/Absolute_Radio).
Fun fact. My college radio station had the station ID WTBS (technology broadcasting system or something like that). When Ted Turner was spearheading one of the fairly early major cable TV stations, he bought the ID for what I imagine was a lot of money for a college radio station for the Turner Broadcasting System or something similar.
You can think of it as the "smash like and subscribe" of the radio days!