hat the population is able to pick up radio broadcasts to keep them aware of the news and national events. Having a radio station also helps to maintain a sense of national identity. The solution is to use frequencies that enable a greater coverage to be gained. As a result a number of 'tropical bands' are allocated with frequencies up to about 5 MHz. By using the relatively short skip normally present on these bands greater coverage can be achieved. Often transmitters in the medium wave and VHF FM are used for the populated areas while the tropical bands are used to give greater coverage for the outlying areas. The tropical bands are only used by countries between latitudes of 23°N and 23°S. This area covers part of Africa, Asia, Central and South America. With the large amount of pressure on the short wave broadcast allocations it is necessary for broadcasters to make the maximum use of the available spectrum. Although the channel spacing is only 5kHz instead of the greater spacing used on the medium wave band spectrum availability is still tight. To improve the spectrum usage and reduce congestion single sideband transmissions are starting to be used and a gradual changeover is being made. When broadcast stations use SSB, Broadcasting 207 they only transmit one sideband. Also the level of the carrier is reduced by 6 dB which enables major savings to be made in the power required for the transmitter. VHF FM One of the main disadvantages of AM is the fact that the transmissions are subject to interference and noise. The bandwidths used also mean that the audio frequency response is limited. The VHF FM broadcasts offer much higher quality both in terms of the noise performance and frequency response. With a deviation of + 75 kHz the transmissions have an overall transmission bandwidth of 200 kHz. The upper audio frequency limit is generally taken as 15 kHz for these transmissions. This is quite adequate for most high quality transmissions. One of the problems with these high quality VHF FM transmissions is that t