short-wave reciever - the world in your pocket

short-wave receiver . elektor may 1984 Broadcasting on short waves is confined to a number of relatively narrow bands, usually called wavebands. Although quite a number of high-quality channels (fre- quency separation = 9 kHz) can be ac- commodated in each band, there are so many short-wave stations that satisfactory reception is frequently impossible unless you have a very selective receiver. The use of specific frequencies for long- distance transmission is determined largely by ionospheric conditions which, in turn, depend on the eleven-year sunspot cycle. Schedules of transmission times and frequencies are worked out with reference to the ionspheric condi- tions at particular times of the day and year and are published by most broad- casting organizations (for overseas readers: `London Calling" issued by the BBC). The receiver is a double superhet with preselector. In superheterodyne radio reception the incoming signal is mixed with the signal from a local oscillator. This res...