Interesting lists here. The FCC lists of silent AM and FM stations that have been off the air for at least two months.
More silent FM's than AM's, which surprised me. Links to the lists are here:
https://www.fcc.gov/media/radio/silent-radio-lists
TIB
A local group owns two AM stations, 590 and 1380.
For a year or more 590 was silent following a fistfight in the station's hallway involving management staff which made the news. Truth is I don't know if the fight was connected to the silence, but I was all set to claim 590 for carrier current when suddenly it came back.
590 is only 1 kW directional and is rather far out of town so it's not a station that's easy to hear, but when they got it re-started their 1380 signal went off and I see it on Tim's list.
1380 locally is licensed for 5 kW day 1 kW night and has a legendary history, until it began sliding in ratings with no one able to re-kindle the old spirit.
In its prime it was KWK owned by the St. Louis Globe Democrat with the programs of the Mutual Network.
During the rock years in the 60s King Richard was a top rated talented DJ in the evening, not held back at all when running only 1 kW.
Another local show from KWK was Jack and Jerry's Cityrama, a station wagon that would show up at public locations with a live remote using some shortwave frequency to hop back to the station (or so I thought). They had a very tall whip antenna on the bumper. I walked over to be on Cityrama one evening when it was parked at a nearby hotel. No memory whatsoever of what was said when they talked to me on mic.
They were probably using a Marti remote transmitter to send their programming back to the studio. We use one regularly, and ours dates from the 1970's and I know they were around much earlier than that. Ours is solid state, vintage tube models exist. Ours is VHF, 162. something MHz if I recall. 52 watts output on FM. We get about a ten mile range with a short whip antenna depending on terrain. We have a mic stand mounted yagi for a directional signal if we need a bit more coverage.
TIB
The first commercial station I worked at used a Link (tube-type) RPU....it had an 829B in the final.....get a nice, HOT summer day.....and that thing would drift off frequency in about 5 minutes...an entire high school graduation broadcast was ruined because of this....nothing but muffled grunts audible as the grad's names were read.....!!! The station, needless to say, took a lot of flak for that one!!:(
I also remember that the Cityrama station wagon was equipped with a power generator... their street broadcasts sounded like they were on board a propellor airplane.