Editing International broadcasting (section)

=== <span class="anchor" id="shortwave_broadcast_anchor"></span>Shortwave broadcast ===
[[Shortwave receiver]]s are capable of receiving [[shortwave]] transmissions (2,000 to 30,000&nbsp;kHz or 2 to 30&nbsp;MHz). Depending on time of day, season of year, solar weather and Earth's geomagnetic field, a signal might reach around the world.

[[Image:RCI-BC-ANZ431-dbu.png|thumb|300px|This sort of map is used by radio engineers to determine the best frequencies to reach international audiences on shortwave bands. In this case, a transmitter is sited in the Southern [[Vancouver Island]], using a frequency of 12095 kHz and transmitting at the 500 kW power level. The picture shows a good signal over the Southern Pacific. The signal fades out as it approaches the [[Eastern states of Australia|East Coast of Australia]].]]

In previous decades shortwave (and sometimes high-powered mediumwave) transmission was regarded as the main (and often the ''only'') way in which broadcasters could reach an international audience. In recent years the proliferation of technologies such as satellite broadcasting, the Internet, and rebroadcasts of programming on AM and FM within target nations has meant that this is no longer necessarily the case.

Transmitter output power has increased since 1920. Higher transmitter powers do guarantee better reception in the target area. Higher transmitter power in most cases counteracts the lesser effects of [[radio jamming|jamming]].
* 1950s : 100&nbsp;kW
* 1960s : 200&nbsp;kW, early 1960s (2 × 100&nbsp;kW 'twinned')
* 1970s : 300&nbsp;kW, but many 250&nbsp;kW transmitters sold
* 1980s : 500&nbsp;kW sometimes transmitters were "doubled up" to produce 1000&nbsp;kW output
* 1980s-present: 600&nbsp;kW single, 1200&nbsp;kW from twinned transmitters.

International stations generally use special [[HRS type antennas|directional antennas]] to aim the signal toward the intended audience and increase the [[Effective radiated power|effective power]] in that direction. Use of such antennas for international broadcasting began in the mid-1930s and became prominent by the 1950s. By using antennas which focus most of their energy in one direction, a modern station may achieve the equivalent, in that direction, of tens of millions of [[watt]]s of radio power.