Electronics - Lessons

1-TRANSISTOR AM RADIO RECEIVER: A PERFECT PRACTICE PROJECT Building a 1-transistor AM radio receiver is an absolute classic in the world of electronics. It is one of the most rewarding practice projects for beginners, bridging the gap between a basic crystal radio and a fully amplified superheterodyne receiver. Below is a detailed breakdown of the components and the circuit operation. Transistor (Q1): An NPN transistor (such as the popular 2N2222, BC547, or BC108) acts as the audio signal amplifier. Diode (D1): A Germanium diode (like the 1N34A). Note: Germanium is crucial here! Unlike silicon diodes (which drop 0.7V), germanium diodes only drop 0.2V-0.3V, making them sensitive enough to demodulate weak AM radio frequency (RF) signals. Audio Transformer (T1): An output matching transformer. It matches the high output impedance of the transistor's collector to the low impedance (usually 8 ohms) of the speaker. Capacitors: C_tun...

UNDERSTANDING CRYSTAL OSCILLATORS: THE HEARTBEAT OF DIGITAL ELECTRONICS In digital electronics and radio engineering, timing is everything. Just like a human heart keeps a steady pulse, a digital circuit requires a highly precise and unwavering time base to coordinate its operations. This vital function is performed by a fundamental electronic component: the Crystal Oscillator . Below is a detailed breakdown of how this remarkable component works, its internal structure, and its key applications in modern technology. Pierce Crystal Oscillator Circuit INV XTAL Quartz Crystal C1 C2 Stable Clock Output Uniform Square Wave for Digital Circuits Fig 1. Standard Pierce Crystal Oscillator configuration and its square wave output. 1. What is a Crystal Oscillator? A Crystal Oscillator is an electronic oscillator circuit that uses the mechanical r...

TRANSISTOR AUDIO FREQUENCY AMPLIFIERS. POWER AMPLIFIERS By the request of site visitors, I present an article entirely dedicated to transistor amplifiers. In, we briefly touched upon the topic of transistor amplification stages, so with this article, I will try to fill in all the gaps regarding transistor amplifiers. Some of the theoretical foundations presented here are valid for both transistor and vacuum tube amplifiers. At the beginning of the article, we will overview the main types and methods of connecting amplifier stages. Later, we will look at the main pros and cons of single-ended transformer and transformerless amplifiers. We will also pay special attention to push-pull transformer and transformerless amplifiers, as they are widely used and of great interest. Finally, just like in previous lessons, there will be practical work at the end. This article does not differ from the regular lessons, with the only difference being that this and all subsequent articles will...

MULTIVIBRATOR AND ITS APPLICATIONS This lesson will be dedicated to a quite important and highly demanded topic: multivibrators and their practical applications. If I tried to just list where and how astable (free-running) symmetrical and asymmetrical multivibrators are used, it would take a good number of book pages. There is perhaps no branch of radio engineering, electronics, automation, pulse, or computer technology where such generators are not applied. In this lesson, theoretical information about these devices will be given, and at the end, I will provide several examples of their practical use for your DIY projects. Astable Multivibrator Multivibrators are electronic devices that generate electrical oscillations with a shape close to a rectangular wave (square wave). The spectrum of oscillations generated by a multivibrator contains many harmonics — which are also electrical oscillations, but multiples of the fundamental frequency. This is reflected in its name: mul...

P-contour Calculator for Power Amplifiers Pi-network calculation based on the methodology of I. Goncharenko (DL2KQ). To start the calculation, set your values for frequency F , source impedance R1 , load impedance R2 , unloaded coil Q-factor Qxx (assuming the unloaded Q of capacitors C1 and C2 is much higher than that of L, which is true for most capacitors), and your desired loaded Q-factor Qh . Then, click "Calculate". For a tube amplifier operating in class AB with a small idle current, the source impedance R1 can be roughly estimated using the following formulas: For the anode circuit, R1 ≈ Ea / (1.8 * Ia) (where Ea is the DC anode voltage and Ia is the maximum DC anode current) or R1 ≈ Ea² / (2.5 * P) (where P is the maximum effective output power). For the input Pi-network of a grounded-grid PA, R2 ≈ 1/S (where S is the tube's transconductance). The approximation of R1 is related to the conduction angle ...

Calculation and Manufacturing of a Crystal Filter ▶ You can discuss the video directly on the YOUTUBE channel in the comments section Building Crystal Filters at Home: A Complete Practical Guide 1. Introduction and Objectives A crystal filter (CF) is a key component of any modern superheterodyne transceiver or receiver, determining the adjacent-channel selectivity in the intermediate frequency (IF) stage. In this article, we will break down the methodology for creating a high-quality CF, allowing even a beginner radio amateur to achieve professional results with minimal costs. The main focus is on practical implementation: from laboratory measurements of quartz crystal parameters to the final tuning of the finished product using modern, accessible instruments. 2. Required Equipment and Materials To implement this project using an "engineering approach", you will nee...