So far, we have discussed the basic electronic components, and power supply circuits. We have touched on filters, but not discussed them in detail. No course on electronics would be complete without a thorough understanding of filters, how they work, and how to recognize them when you see them.

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Before going into the specifics of how a Klystron tube works, we must first understand it’s basic parts. Which reminds me of a story….

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Thomas Edison, famous (at least in America), for inventing the light bulb, made many discoveries before he completed his task of lighting the path of the world. Along the way, he incidentally noted that if a filament were energised within a vacuum, that after time, a “shadow” would be left on the inside of the glass, which resembled the shape of the filament.

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Now that we have caught up on basic tube theory, and understand how a beam of electrons can be formed in a vacuum, we are well on our way to understanding how a KLYSTRON operates.

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Sounds like a great title for a science fiction novel, doesn’t it? Well, perhaps another time. But now we are going to discuss some of the intricacies and dangers of klystrons.

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Another important factor when dealing with klystrons is heat. Not all of the developed in the cathode becomes radiated output. Much of the energy is dissipated as heat. If the tube gets too hot, it can become a hazard to itself. Temperature sensors are placed in various places to shut down the tube in the event of overheating.

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In the last section, we saw how a very simple transmitter worked. It was made up of several different types of electronic components, including capacitors, transistors, resistors, etc. When we assemble several types of electronic components in a configuration that serves some purpose, we call it a CIRCUIT.

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Knowing what a diode is, or how a triode works is of little use unless you have some practical knowledge of how it can be applied within a circuit. We are going to begin with a VERY basic schematic of an early transmitter. Do NOT try to build this at home!

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Up to now, you have learned something about the diode vacuum tube and how it works. The most important point to rember about the diode is that it only allows current to flow IN ONE DIRECTION.

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As discussed in the previous lesson, a Characteristic Curve is found by applying several different voltage levels, and measuring plate voltages vs. plate current. We note that in a diode, if we go below a certain plate voltage, ( in this case 0 volts ) no plate current flows. The minimum point at which the tube no longer operates is called the CUTOFF POINT.

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