Valve oscillator circuit 100 Metres and Below

  
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The congestion of the ether is becoming so great that efforts are continually being made to extend the channels of communication to higher frequencies. Wavelengths as low as 12 metres are now commonplace, but attempts to work below this are fraught with many difficulties. At about one metre the period of oscillation is comparable with the time tha
Valve oscillator circuit 100 Metres and Below - schematic

t the electrons take to pass from electrode to electrode in the valve, and the ordinary valve-oscillator theory breaks down. The accompanying article outlines the history of short-wave communication and summarises the position today. The fundamental oscillator circuit. If grid and anode circuits are in resonance the electrostatic coupling produced by the valve`s electrode capacity is sufficient to cause oscillation. Since the War (1914-18), on account of the increasing congestion in the field of radio communication, attempts have been made to extend in every possible direction the range of frequencies available for this purpose. At the close of the War the generally used wavelengths ranged between 100 and 20, 000 metres (3, 000 to 15kHz), Since the 10-15 kHz range verges upon the audio frequency spectrum, there was obviously no room there for extension, so wavelengths had perforce to be found in the zone below 100 metres (above 3, 000 kHz). How the use of wavelengths below 100 metres and down to 15 metres was developed is now a matter of fairly common knowledge. Of course, there was one great advantage in the possibility of using ultra-short waves, apart from the relatively efficient aerial systems which could be used in connection with them, ie, the fact that stations could be packed closer (since the spacing was a matter of frequency difference) as the wavelength was reduced. Even so, the waveband between 15 and 100...



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