A 52 MHz third overtone crystal is typically 30 ohms at its series resonance according to manufacturer specifications. The crystals used for the prototypes have nearly ten times lower series resistance but they were very expensive. An oscillator can be seen as an amplifier which has feedback through a filter. The amplifier of a series resonance os
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cillator must have both a low input impedance and a low output impedance, preferrably well below the series resonance impedance of the crystal, to preserve the selectivity associated with the high Q of the crystal itself. Since this oscillator is used at a higher frequency the amplitude of the oscillations is controlled by a limiter to make the transistor run in class AB. This gives a good compromise between the wideband noise floor and the close in phase noise. Class C is good at low frequencies but a bad idea for VHF oscillators, particularly if they are intended to be used to generate microwave frequencies. Class A amplifiers give the best close in performance and should be used for microwave frequency multiplier chains. The output impedance of the selected MPSH10 transistor is stepped down by a factor of about 20 in a LC resonant circuit. The coil, L14, is 5 turns of 1. 2 mm enameld wire. The coil is wound on a 7 mm rod and mounted self supporting on the PCB with a distance from the copper to the PCB of 3 mm. The length of the coil is 11 mm. It is essential to feed the amplifier Q5 from a low impedance to make the noise generated in this transistor low. The MPSH10 transistor generates very little noise because of the large current feedback on the emitter. Except at the frequency of series resonance the impedance seen by the emitter is high and loss-less. The frequency of oscillation is adjusted with a trimmer in series...
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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