I understand you're looking for a "good piece" (likely a review, summary, or analysis) on the book Radio Engineering by G.K. Mithal, specifically the PDF version.

Here’s a concise, helpful breakdown of what this book is, its strengths, weaknesses, and where it stands among radio engineering textbooks.

Module D: Radio Transmitters and Receivers

• AM/FM Generation: Armstrong method and Reactance tube modulators.
• Superheterodyne Receiver: The block diagram approach is vital. Focus on Image Frequency rejection and tracking errors.
• Noise: Calculation of Noise Figure (NF) and Signal-to-Noise Ratio (SNR) for cascaded stages.

Module B: Radio Wave Propagation

• Modes of Propagation: Ground wave, Sky wave, and Space wave.
• Ionospheric Layers: D, E, and F layers and their effect on radio waves.
• Critical Frequency & MUF (Maximum Usable Frequency): Memorize the formulas here. Numerical problems often ask to calculate the skip distance or the MUF given the electron density.

Unit 2: Oscillators (The Heart of Radio)

• Barkhausen Criterion.
• Hartley, Colpitts, Clapp, and Crystal oscillators.
• Frequency stability and drift.

What makes it a "good piece" (Strengths)

1. Exam-oriented & straightforward – Concepts are explained in simple language, without heavy mathematics. Ideal for quick revision and passing university exams.
2. Affordable & accessible – Widely available in India as a low-cost paperback; PDF copies are easy to find (though often of varying scan quality).
3. Numerous solved & unsolved problems – Great for practice, especially for numericals on tuned circuits, modulation index, power calculations, etc.
4. Covers older technologies well – Excellent for understanding vacuum tube circuits, early transistor RF designs, and legacy radio systems (still relevant for history or hobbyist restoration).
5. Viva voce / short question-answer sections – Many editions include "review questions" at chapter ends, helpful for interviews or practical exams.

2. Key Chapters & Core Concepts

If you are studying from this text, here are the critical modules you should focus on:

1. Book Overview

G.K. Mithal’s Radio Engineering is renowned for its exam-oriented approach. Unlike heavy theoretical texts, this book focuses on:

• Concise Theory: Straight-to-the-point explanations.
• Solved Examples: A large number of numerical problems which are crucial for university exams.
• Exam Questions: It frequently compiles questions from previous years' university exams.