A SIMPLE APPROACH FOR BLACK-OUT PROBLEM

Antennas surrounding by the plasma medium does not radiate for all tIie frequencies but only for those which are greater than the plasma frIJquency. Here we have proposed a cylindrical (axiall:y magnetized) antenna system which radiates for all frequencies irrespective of plasma frequency and this is the solution for the black-out situa-tion which occurs for certain frequencies. The interaction of electromagnetic wa ves with the ionised gases in the ionospheric plasma is a very important field of research for the communication engineers.-The information carried by a modulated electromagnetic wave may be absorbed or even completely destroyed (black-out), when the wave travels through a plasma media. Radiation leaving an antenna on earth need not travel very far before it e~-counters the natural plasma in ionosphere. Various a uthors 1-4- ha ve proposed the electronically scanna ble plasma antenna systeinin which the direction of the radiation peak is scannable by the plasma density. However in these studies, the radiation is not obtained for all frequencies. In this paper, we have proposed in, antenna system which radiates for all frequencies and hence black-out can be removed. To overcome the problem of the black-out, we have proposed an antenna system which contains an axially magnetized cylindrical, one component semiconductor plasma consisting only of electrons (e.g. n., In Sb), of radius situated such that its longitudinal axis corresponds to the z-axis of the cylindrica