So I'm around 4 km away from the City-Airport Mannheim (EDFM/MHG). Various websites tell me that its ATIS frequency is 136.550 MHz.
When I tune to 136.550 with my VHF AM receiver, I can see a strong carrier, with no modulation at all. I've listened to it for several hours, on different weekdays and during different times of day.
So my question is: Is this usual behavior or not? I'm aware that the airport in question doesn't see much traffic, but I'd sort of expect the ATIS to be either running, when needed, or switched-off, when not needed.