In Tesla's time it was main topic. The efficiency of an antenna was the diameter of the wire dependent. The thinner is better. But too thin was melting. There were the such lamps. Now everybody know how to do "local TV station".
At the end of antenna the field electron emission take place. The surface condition is extremally important: ""In the early years of the 21st century there has been renewed interest in vacuum tubes, this time with the electron emitter formed on a flat silicon substrate, as in integrated circuit technology. This subject is now called vacuum nanoelectronics. The most common design uses a cold cathode in the form of a large-area field electron source (for example a field emitter array). With these devices, electrons are field-emitted from a large number of closely spaced individual emission sites."
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