All American 5

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3/1/20 Hi tube enthusiasts interested in RF with tubes. A brief: -Edison invented the light bulb. -Fleming of UK imported Edison's bulbs. -Fleming played with a bulb and placed a second element inside. -Using batteries, he discovered electrons moved inside the bulb. Eureka! The DIODE! -Back in the U.S.A., a third element was discovered to control the flow of huge electrons with TINY currents. EUREKA! THE TRIODE. It was originally called the AUDION. So, it is CATHODE,GRID,PLATE. -Electrons moved fast inside the tube, i.e. at high voltage, 45 volts upwards. Armstrong, American, was first to experiment RF in a tube. He used the basic t riode as an RF amplifier. He invented the REGENERATIVE RECEIVER.
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A coil with a capacitor across it is called a tank and is tuned to a certain frequency. Armstrong fed the signal from such coil into the grid of a triode to amplify it. He discovered that by feeding some of the amplified signal back into the grid, regeneration occurred, making the signal even loader. His invention got a worldwide recognition and this was called the REGENERATIVE RADIO OR REGEN for short.
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The problem with the Regen radio was that it was fidgety and lacked selectivity. The next type of tube radio then was called the TRF for Tuned radio frequency. The idea was a series of amplifiers each with a tuning coil. There were just too many tuners! But it can fine tune to a station. It was still figedty to the taste and something has to be developed to make a USER FRIENDLY radio. Armstgrong went back to the drawing board. He knew the principle that frequencies can be MIXED. His goal was go reduce the number of tuning condensers. Finally, he invented the SUPERHETERODYNE radio when a local oscillator is mixed with the incoming signal. The tuning capacitors of the antenna coil and the oscillator coil were ganged. The differential frequency was kept constant at 455 Khz. The next amplifier as tightly tuned to 455 Khz. Till today, this principle is still used. Superhets spread all over the world and in the U.S.A., the most common was a five tube set up. It was called the All American...
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