Table of Contents

Preface to the 5th Edition xi

In Memoriam xiii

1 Transformer Basics 1

1.1 Introduction 1

1.2 The Basic Building Block 4

1.2.1 Phase Inverter 5

1.2.2 Balun 5

1.2.3 Delay Line 5

1.2.4 Bootstrap 6

1.3 Designing a Magnetic Transformer 6

References 8

2 Ferrite Materials 11

2.1 Introduction 11

2.2 Ferrite Physical Properties 12

2.3 Ferrite Permeability 13

2.4 Magnetic Losses 16

2.5 Ferrites and Frequency Response 18

2.6 Power Ratings 19

2.7 Suppliers of Materials 25

2.8 Additional Reading 25

References 25

3 Guanella Analysis 27

3.1 Introduction 27

3.2 Mid-Band Operation 27

3.3 Low Frequency Operation 30

3.4 Guanella Transformer Variations 32

4 Ruthroff Analysis 35

4.1 Introduction 35

4.2 Low Frequency Analyses of Ruthroff's 1:4 Transformers 39

4.3 High Frequency Characterization 41

Reference 42

5 Transmission Line Construction 43

5.1 Introduction 43

5.2 Commercial Transmission Lines 43

5.3 Custom Coaxial Transmission Lines 43

5.4 Custom Parallel Transmission Lines 45

5.5 Closely Wound Twin Lead 50

5.6 Three Conductor Lines 51

5.7 Custom Multiconductor Transmission Lines 54

5.8 Comparison of Twisted Pair and Twin Lead 55

5.9 Long Transmission Lines 58

5.10 Variable Characteristic Impedance Lines 58

References 59

6 1:4 Unun Transformer Designs 61

6.1 Introduction 61

6.2 Schematics and Pictorials 62

6.3 12.5.50 Ω Ununs 64

6.4 25:100, 50:200, and 75:300 Ω Ununs 69

7 Unun Transformer Designs with Impedance Ratios Less Than 1:4 73

7.1 Introduction 73

7.2 1:1.5 Ununs 75

7.2.1 Tapped Bifilar Transformers 76

7.2.2 Quintufilar Transformers 79

7.3 1:2 Ununs 85

7.4 1:3 Ununs 96

8 Unun Transformer Designs with Impedance Ratios Greater Than 1:4 99

8.1 Introduction 99

8.2 Guanclla Transformers 100

8.2.1 5.56:50 Ω Ununs 102

8.2.2 50:300 Ω Ununs 103

8.2.3 50:450 Ununs 104

8.2.4 50:600 Ω Ununs 104

8.2.5 50:800 Ω Ununs 107

8.3 Ruthroff-Type Transformers 107

8.3.1 5.56:50 Ω Ununs 111

8.3.2 50:450 Ω Ununs 113

8.3.3 3.125:50 Ω Ununs 114

8.4 Ruthroff-Guanella Transformers 116

8.5 Coax Cable Transformers-Ruthroff Type 117

Reference 119

9 Baluns 121

9.1 Introduction 121

9.2 The 1:1 Balun 121

9.2.1 Rod versus Toroidal Baluns 126

9.2.2 Bifilar versus Trifilar Baluns 127

9.2.3 Air Core versus Ferrite Core Baluns 129

9.3 The 1:4 Balun 129

9.3.1 50:200 Ω Baluns 133

9.3.2 75:300 Ω Baluns 136

9.3.3 25:100 Ω. Baluns 137

9.3.4 12.5:50 Ω Baluns 138

9.4 The 1:9 Balun 139

9.5 Baluns for Yagi, Quad and Rhombic Antennas 142

9.5.1 Yagi Beams 142

9.5.2 Quad Antennas 143

9.5.3 Rhombic Antennas 144

10 Multimatch Transformers 147

10.1 Introduction 147

10.2 Dual-Output Transformers 148

10.2.1 1:1.5 and 1.3 Ratios 148

10.2.2 1:2 and 1:4 Ratios 151

10.3 Parallel Transformers 153

10.4 Eight-Ratio Transformer 155

11 Equal Delay Transformers 157

11.1 Introduction 157

11.2 The Need for Fractional Ratio Transformers 157

11.3 The Equal Delay Transformer 158

11.4 Integer [n²] Ratio Equal Delay Transformers 160

11.5 Fractional [(n/m)²] Ratio Equal Delay Transformers 161

11.6 Unun versus Balun Equal Delay Transformers 162

11.7 Calculation of Impedance Transformation Ratios 163

11.8 Achievable Transformation Ratios 165

11.9 A 50-75 Ω Equal Delay Unun Example 168

11.10 Performance of the 50-75 Ω Transformer 170

References 172

12 Simple Test Equipment 173

12.1 Introduction 173

12.2 Transformer Impedance Measurement 173

12.3 Transmission Line Impedance Measurement 174

12.4 Home-Built Equipment 177

12.5 The Wheatstone Bridge 178

12.6 A High-Frequency Resistive Bridge 179

12.7 Signal Generators 182

12.8 Efficiency Measurements-The Soak Test 184

12.9 Characteristic Impedance Measurements 185

References 187

13 Construction Techniques 189

13.1 Introduction 189

13.2 Selecting Ferrites-Substitutions 189

13.3 Winding Rod Transformers 190

13.4 Winding Toroidal Transformers 191

13.5 Constructing Low Impedance Coax Cable 192

13.6 The Care and Handling of Ferrite Transformers 194

Appendix A Reprint of Guanella Article 195

Appendix B Some Broad-Band Transformers 201

Index 217