One of the outstanding problems in the design of vacuum-tube oscillators is that of keeping the frequency constant despite mechanical vibrations, temperature changes, voltage variations in the supply lines, and changes in the amount of power taken out of the circuit by the load. The effects of variable loading are greatly reduced by the use of electron coupling. Let us imagine that in the Hartley
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circuit of Fig. 14 B the actual metal plate is replaced by a grid of wires. The stream of electrons reaching this electrode increases and decreases in number at the frequency of the oscillating circuit in the usual manner. But, with a grid of wires rather than a solid metal plate, a part of this stream of fluctuating electrons passes through the " plate " and can be used in a later portion of the tube. It is as though we had a " virtual" cathode, emitting electrons, whose number varied from maximum to minimum periodically at a high rate. Of course it is impossible to heat and cool an actual cathode at high frequencies. Yet the combination of the Hartley circuit with a grid which acts as the " plate " serves the same purpose. In the circuit on the left of Fig. 29 A, the fluctuating electron current, which has passed through the grids, reaches the solid plate and passes on to the tuned circuit LC. When the periodic fluctuations of the electron stream correspond to the natural frequency of the tuned circuit, they serve to supplant the losses in this resonant or tank circuit and keep it in oscillation. An important feature of this arrangement is that the upper grid is operated at ground r. f. potential, and hence acts as a shield between the output or load circuit coupled to LC and the oscillating circuit itself. In this way, variations in the load current are prevented from reacting upon the oscillator circuit and changing...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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