The signal is sent by microwave to a similar microwave receptor on the grounds where the tranmitter and tower are. It is then converted into a signal that is broadcast to the general public. It is not uncommon for a Radio station's studios to be located 10, 15 even 30 miles away from the actual transmitter and tower.
You'll notice there are several microwave dishes on this tower. That's because it is relaying signals for several different Radio stations.
