An Avon Fire and Rescue Service spokesman said: "This was a couple of sheds, or outbuildings, on fire, off Golf Course Road. We were called at around 5.45am and several appliances from Bath fire station are on the scene.
"I believe this may be affecting radio and possibly television transmissions in the area at the moment.
"Police have also been called as the early indications are that this fire may have been deliberately started."
Customers getting TV via Sky were unaffected, as were people in the south of the city whose TV signal comes from the Mendip transmitter near Wells.
A spokesman for Avon and Somerset Police said: "At this stage we believe it may have been started deliberately. It is not known exactly where the fire started, however we are appealing for anyone who saw people acting suspiciously in the area in the early hours of today to contact police on 101."