Where your broadcast will be heard when broadcasting on shortwave depends on a number of factors like power of the transmitter, type of antenna, time of the day, season, frequency used and distance between transmitter site and listening place.
The power of the transmitter is an important factor and can range from 50 kW up to 500 kW. More background information about shortwave radio broadcast transmitters can be found at Shortwave Radio Broadcast Transmitters.
Another important factor is the choice of a proper antenna. Background information about shortwave radio broadcast antennas can be found at Shortwave Radio Broadcast Antennas.
As an indication, a 50 kW shortwave transmitter can cover a country, with a 100 kW shortwave transmitter, you can cover a small continent close to the transmitter location, with a 250 kW shortwave transmitter you can cover a continent further away and with a 500 kW shortwave transmitter, you can broadcast to each part of the world.
Since shortwave radio uses the changing ionosphere to broadcast its signals, it is not possible to broadcast at each hour of the day from one transmitter site to every possible location on earth.
Also, it is not always possible to use the same frequency for each hour of the day or to use the same frequency in the winter and summer season.
Therefore a careful selection of transmitter location, time and frequency is important when targeting a particular audience or country.
Alyx & Yeyi has transmitters located around the world and with different power levels, so that we are able to reach any destination on earth under the best circumstances possible.