Overview

Valve Amplifiers Explained

This new book by John Fielding, ZS5JF, is for everyone who uses, or is considering using, an HF or VHF linear amplifier. While some amateurs may be of the opinion that valves are an obsolete technology and semiconductors are a better way, Fielding very definitely thinks otherwise! After reading the 200-page paperback you'll be under no illusions that, in his opinion, valves are far superior to semiconductor devices for most linear amplifier applications. As he says, "When you need real power and very good linearity, a valve is very hard to beat."

Essential reading for anyone building a valve linear amplifier, the author guides you through the choice of valves for various purposes. "Valve Amplifiers Explained" starts with a chapter on basic valve theory and explains how to interpret valve characteristic curves. The various classes of operation of amplifiers—Class A, Class B, Class AB1, Class AB2, and Class C—are all covered in detail. The relative merits of grounded cathode and grounded grid amplifiers are discussed, and a chapter is devoted to the causes of distortion in valve amplifiers (and how to avoid such distortion). Fielding explains that linearity is primarily a function of the power dissipation of the device and the supply voltage—and he devotes a whole chapter to good power supply design. The various protection circuits that an amplifier should have are also covered. While this book is equally relevant to HF and VHF enthusiasts, a chapter is devoted specifically to the design of VHF RF power amplifiers. Another chapter even discusses liquid cooling of valve amplifiers.

There is advice too for those who, instead of building an amplifier, are considering purchasing a commercially made linear. Those who use commercial linear amplifiers and want to understand more about how they work will not be disappointed. As Fielding says, "There is a certain aura about valve equipment. The glowing filaments and the gentle buzz of a high voltage power supply are a sort of magic few have had the pleasure of knowing." After reading "Valve Amplifiers Explained," you'll want to join that elite few!

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