What range can I get?
The power you need depends on the geographical terrain and how high your antenna is mounted.
Radio signals are radiated from the antenna, not the transmitter. Given this, if you mount the antenna higher, the antenna can see further and you will get further range. Another good rule of thumb is that if you increase antenna height by 3 times the antenna will see double the distance, therefore potentially doubling the range if you have enough power.
If you look at a very powerful light, it can been seen more clearly from a very great distance, the radiating antenna behaves very similar to this. If you have a very powerful transmitter you will get further range if you have the antenna height. Power is good for penetrating obstacles that get in the way of the radio signal, it also improves the transmission quality in stereo.
The biggest problem to range is the curvature of the Earth. Because 88-108 MHz signals radiate in straight lines, like light, as the Earth curves the signal is then blocked. Through experience we have found that this occurs between 35 miles (50 Km) and 50 miles (75 Km) on flat land. Assuming you are on flat land, with no hills or mountains and your antenna is mounted about 20 meters high you would typically get 30 miles (45 Km) from 200W ERP, 40 miles (60 Km) from 400W ERP and around 50 miles (75 Km) from 1600W ERP. If you mount your antenna on a tower block or very high mountain you may be able to get between 50 miles (75 Km) and 100 miles (150 Km) range with 1600W ERP.