The overall performance of any rf circuit in regards of it`s phase noise and spectral purity depends significantly on the frequency generating circuitry, commonly an oscillator. Low noise oscillators with high spectral purity are neither witchcraft nor black magic. Many people think the design of oscillators is black magic as such circuits usually
Click here to download the full size of the above Circuit.
either work or not. Especially beginners are glad when they finally get a circuit to oscillate and attributes such as signal quality are usually secondary and often neglected. This article is going to show two easy tricks that can be implemented in almost any oscillator design. To be precise, the oscillator is a Miller crystal oscillator. In case you are wondering where the LC tank circuit in the collector path of T1 is, look closer! The inductor L1 has an unavoidable capacitance known as parasitic capacitance` or stray capacitance`. I personally prefer the term parasitic capacitance because the term stresses that the capacitance is a (usually) unwanted phenomena. Parasitic capacitance is the reason why inductors have a self-resonance frequency (SRF) mentioned in their datasheet. The first step is to improve the power supply. Usually circuits in the amateur radio community use some sort of linear voltage regulator to stabilize the supply voltage to a fixed voltage. Linear voltage regulators have the unfortunate habit of introducing a significant amount of noise into the system. [ 1 ] It should be apparent that a high noise floor in the supply voltage has a direct influence on the output signal of an oscillator. The noise directly modulates the oscillator circuit and produces plenty of phase noise. Luckily, there`s an easy remedy for this problem; a low pass filter. A simple RC low pass filter, consisting of R1 and C3, on...
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.....
characters left: