I just always assumed that DirecTV had access to pretty every single area in the country I never really understood that some of the satellite providers only limited to certain small areas of the state and sometimes it doesn't even encompass a few cities.
With non-local channels this is true as they are on a frequency which is configured to cover most of the North American continent. These frequencies are referred to as ConUS transponders which stands for Continental US.
However with the sheer amount of local TV network affiliates across the United states (over 2,000), there would never be enough satellite capacity to carry all of these using ConUS transponders which is why spotbeam transponders are used instead in order to carry the local network affiliates for each city.
Spotbeams differ from ConUS transponders in the sense that they have a a limited coverage area focused on a specific region. This allows for the frequencies assigned for spotbeams to be reused in many different areas across the country which substantially increases capacity and provides the ability for the satellite provider to carry the major network affiliates for each city in the U.S.
Coverage map of spotbeams used by DirecTV to deliver local channels across the United StatesThis explains why someone who is located outside the coverage area of the spotbeam that serves their local channels won't be able to receive them but all other non-local channels will work fine. Normally this is not an issue as the FCC in the U.S. normally only allows access to the local network affiliates serving their market which would fall within the spotbeam's coverage.
Both DirecTV and Dish Network make use of spotbeams in order to carry local channels.
