1) Two interesting public goods are radio and television signals

A) In the US, private markets have provided these public goods because a private good is associated with radio and television signals: advertising. Revenue from advertising makes it possible for private firms to provide the public goods - radio and television broadcasts. Explain why these are public goods.

B) How does cable television, which provides television channels to people who pay for a cable into their home, alter the nature of the good called television signals? Explain how, with the advent of cable, television signals are still like public goods, and how they are more like private goods than they were.