Virtually anyone can broadcast over the airwaves today thanks to the increased accessibility of equipment. In the past, the high cost of acquisition kept this in the hands of a few. Now it is possible to get decent machines for a fraction of their original cost. Thus, a person can create his own mini station from home if he really wants to. Note that the truly top-level equipment will require a license of operate in most areas. Smaller ones may not need to go through this process. The coverage area will depend on a few factors including the following:
Power
Small low power FM transmitters are available for personal use. Their range may only be a few yards in diameter. They are good for the car and the home if you wish to connect your media player remotely to a set of speakers. More serious transmitters can potentially reach several miles in every direction. These are usually used by campus radio stations and other local outfits that which to reach out to their community. Finally, a station can use a High Power FM Transmitter which can take the waves many miles across to cover whole cities and beyond. It will all depend on the rating of the machine as measured in watts. A single watt is good for 2 miles while 100 watts can reach 25 miles. Some stations can transmit using hundreds of kilowatts.
Terrain
The terrain of the region will also have a massive effect on the coverage area. If the target audience is in a flat city and you can place the transmitter high above on a hill, then you can reach almost every household in the vicinity. The higher the antenna, the better the reception as well. The transmitter should be at the highest point in the region to make sure that nothing will block the signals. If it were located down below, then the signals will drop when they encounter a hill, a mountain, and other natural barriers. Stations pay a large sum to buy such properties or rent them from the owners.
Buildings
In urban areas, the biggest issue will be the height and density of the buildings around the station. It is for this reason that most of them are situated at the top of skyscrapers and other high towers. While this can improve broadcast, the reception inside buildings can be compromised as well because of the dampening property of the structures. If the occupants want to listen to the stations, then they may have to install an outdoor antenna that can receive the signals clearly.
