Build Your Own Transistor Radios: A Hobbyist's Guide to High-Performance and Low-Powered Radio Circuits - Softcover

QUAN, Ronald

Softcover

ISBN 10: 0071799702 ISBN 13: 9780071799706

Verlag: McGraw Hill TAB, 2012

Inhaltsangabe

Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product.

A DIY guide to designing and building transistor radios

Create sophisticated transistor radios that are inexpensive yet highly efficient. Build Your Own Transistor Radios: A Hobbyist's Guide to High-Performance and Low-Powered Radio Circuits offers complete projects with detailed schematics and insights on how the radios were designed. Learn how to choose components, construct the different types of radios, and troubleshoot your work. Digging deeper, this practical resource shows you how to engineer innovative devices by experimenting with and radically improving existing designs.

Build Your Own Transistor Radios covers:

• Calibration tools and test generators
• TRF, regenerative, and reflex radios
• Basic and advanced superheterodyne radios
• Coil-less and software-defined radios
• Transistor and differential-pair oscillators
• Filter and amplifier design techniques
• Sampling theory and sampling mixers
• In-phase, quadrature, and AM broadcast signals
• Resonant, detector, and AVC circuits
• Image rejection and noise analysis methods

"This is the perfect guide for electronics hobbyists and students who want to delve deeper into the topic of radio. Overall, this extremely well written and comprehensively illustrated guide and reference deserves a place on the inquisitive radio amateur's bookshelf." - QST

"I would definitely recommend this book to novices and all hobbyists and engineers who have not have much practical exposure to radio design and development." - EDN

Make Great Stuff!
TAB, an imprint of McGraw-Hill Professional, is a leading publisher of DIY technology books for makers, hackers, and electronics hobbyists.

Über diesen Titel

Über die Autorin bzw. den Autor

Ronald Quan is a member of SMPTE, IEEE, and the AES. He worked on the design of wideband FM detectors for an HDTV tape recorder at Sony Corporation, and a twice-color subcarrier frequency (7.16 MHz) NTSC vector-scope for measuring differential phase and gain for Macrovision, where he was a Principal Engineer. Ronald currently holds at least 65 US patents in the areas of analog video processing, low noise audio and video amplifier design, low distortion voltage controlled amplifiers, wide band crystal VCOs, video monitors, audio and video IQ modulation, audio and video scrambling, bar code reader products, audio test equipment, and video copy protection.

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Build Your Own Transistor Radios

A Hobbyist's Guide to High-Performance and Low-Powered Radio CircuitsBy Ronald Quan

McGraw-Hill Companies, Inc.

Copyright © 2013 The McGraw-Hill Companies, Inc.
All right reserved.
ISBN: 978-0-07-179970-6

Contents

Chapter One

Introduction

This book will be a journey for both the hobbyist and the engineer on how radios are designed. The book starts off with simple designs such as an offshoot of crystal radios, tuned radio-frequency radios, to more complicated designs leading up to superheterodyne tuners and radios. Each chapter presents not only the circuits but also how each circuit was designed considering the tradeoffs in terms of performance, power consumption, availability of parts, and the number of parts.

In the engineering field, often there is no one best design to solve a problem. In some chapters, therefore, alternate designs will be presented.

Chapters 4 through 12 will walk the hobbyist through various radio projects. For those with an engineering background by practice and/or by academia, Chapters 13 through 23 will provide insights into the theory of the various circuits used in the projects, such as filter circuits, amplifiers, oscillators, and mixers.

For now, an overview of the various radios is given below.

Tuned Radio-Frequency (TRF) Radios

The simplest radio is the tuned radio-frequency radio, better known as the TRF radio. It consists mainly of a tunable filter, an amplifier, and a detector.

A tunable filter just means that the frequency of the filter can be varied. Very much like a violin string can be tuned to a specific frequency by varying the length of the string by using one's finger, a tunable filter can be varied by changing the values of the filter components.

Generally, a tuned filter consists of two components, a capacitor and an inductor. In a violin, the longer the string, the lower is the frequency that results. Similarly, in a tuned filter, the longer the wire used for making the inductor, the lower is the tuned frequency with the capacitor.

In TRF radios, there are usually two ways to vary the frequency of the tuned filter. One is to vary the capacitance by using a variable capacitor. This way is the most common method. Virtually all consumer amplitude-modulation (AM) radios use a variable capacitor, which may be a mechanical type such as air- or poly-insulated variable-capacitor type or an electronic variable capacitor. In the mechanical type of variable capacitor, turning a shaft varies the capacitance. In an electronic variable capacitor, known as a varactor diode, varying a voltage across the varactor diode varies its capacitance. This book will deal with the mechanical types of variable capacitors.

The second way to vary the frequency of a tunable filter is to vary the inductance of an inductor or coil via a tuning slug. This method is not used often in consumer radios because of cost. However, for very high-performance radios, variable inductors are used for tuning across the radio band. In this book, tunable or variable inductors will be used, but they will be adjusted once for calibration of the radio, and the main tuning will be done via a variable capacitor. Figure 1-1 shows a block diagram of a TRF radio.

Block Diagram of a TRF Radio

A TRF radio has a radio-frequency (RF) filter that is usually tunable, an RF amplifier for amplifying signals from radio stations, and a detector (see Figure 1-1). The detector converts the RF signal into an audio signal.

Circuit Description of a TRF Radio

For the AM radio band, the RF filter is tuned or adjusted to receive a particular radio station. Generally, an antenna is connected to the RF filter. But more commonly, a coil or an inductor serves as the "gatherer" of radio signals. The coil (L) may be a loop antenna (see Figure 3-1). A variable capacitor (VC) is used to tune from one station to another.

The output of the filter will provide RF signals on the order of about 100 microvolts to tens of millivolts depending on how strong a station is tuned to. Typically, the amplifier should have a minimum gain of 100. In this example, although the amplifier usually consists of a transistor, a dual op amp circuit (e.g., LME49720) is shown for simplicity. Each amplifier stage has gain of about 21, which yields a total gain of about 400 in terms of amplifying the RF signal.

The output of the amplifier is connected to a detector, usually a diode or a transistor, to convert the AM RF signal into an audio signal. A diode CR1 is used for recovering audio information from an AM signal. This type of diode circuit is commonly called an envelope detector.

Alternatively, a transistor amplifier (Q1, R1B, R2B, and C2B) also can be used for converting an AM signal into an audio signal by way of power detection. Using a transistor power detector is a way of demodulating or detecting an AM signal by the inherent distortion (nonlinear) characteristic of a transistor. Power detection is not quite the same as envelope detection, but it has the advantage of converting the AM signal to an audio signal and amplifying the audio signal as well.

Power-detection circuits are commonly used in regenerative radios and sometimes in superheterodyne radios.

It should be noted that in more complex TRF radios, multiple tuned filter circuits are used to provide better selectivity, or the ability to reduce interference from adjacent channels, and multiple amplifiers are used to increase sensitivity.

Regenerative Radio

This is probably the most efficient type of radio circuit ever invented. The principle behind such a radio is to recirculate or feed back some of the signal from the amplifier back to the RF filter section. This recirculation solves two problems in terms of providing better selectivity and higher gain. But there was another problem. Too much recirculation or regeneration caused the radio to oscillate, which caused a squealing effect on top of the program material (e.g., music or voice) (Figure 1-2).

Block Diagram of a Regenerative Radio

The regenerative radio in Figure 1-2 consists of a tunable filter that is connected to an RF amplifier. The RF amplifier serves two functions. First, it amplifies the signal from the tunable filter and sends back or recirculates a portion of that amplified RF signal to the tunable-filter section. This recirculation of the RF signal causes a positive-feedback effect that allows the gain of the amplifier to increase to larger than the original gain. For example, if the gain of the amplifier is 20, the recirculation technique will allow the amplifier to have a much higher gain, such as 100 or 1,000, until the amplifier oscillates. The second function of the amplifier is to provide power detection of the RF signal, which means that the amplifier also acts as an audio amplifier.

Circuit Description of a Regenerative Radio

In Figure 1-2, the tunable RF filter is formed by variable capacitor VC and antenna coil L1. Antenna coil L1 also has an extra winding, so this is more of an antenna coil-transformer.

Also, because transistors have a finite load resistance versus the "infinite" input resistance of a vacuum tube or field-effect transistor, the base of the transistor is connected to a tap of antenna coil L to provide more efficient impedance matching.

Note

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Details zur Ausgabe

• Verlag: McGraw Hill TAB
• Erscheinungsdatum: 2012
• Sprache: Englisch
• ISBN 10: 0071799702
• ISBN 13: 9780071799706
• Einband: Taschenbuch
• Anzahl der Seiten: 496
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: gpsr@libri.de; gpsr@libri.de; ; Europaallee 1; Bad Hersfeld; 36244; Deutschland