The Radio Sky and How to Observe It (eBook)

Jeff Lashley is a technical support engineer at the National Space Centre in Leicester, UK. He has written regularly for Sunderland and Dundee newspapers. His most recent article on Radio Astronomy was published in the Radio Society of Great Britain magazine Radcom, in January 2007.

Preface 8
Acknowledgements 10
About the Author 12
Contents 14
Chapter 1: The Radio Sun 18
The Solar Core 18
The Radiative Zone 20
The Convective Zone 21
The Photosphere 21
The Magnetic Dynamo 21
The Chromosphere 22
The Corona 22
The Quiet Sun and the Blackbody 23
Solar Flares 24
Classification of Flares 24
How Solar Flares Form 26
Solar Flare Radio Bursts 27
The Quiet Sun 27
The Solar Wind 28
Chapter 2: Jupiter 31
The Structure of Jupiter 31
Jovian Magnetic Field 31
The Jovian Magnetosphere 32
The Inner Magnetosphere 33
The Middle Magnetosphere 35
The Outer Magnetosphere 36
Jovian Radio Emissions 36
Decametric Radio Bursts 37
Interpreting the Jovian Decametric Spectrum 40
Chapter 3: Meteors and Meteor Streams 42
Determination of R 43
Determination of L 44
Determination of C 44
Radio Scattering off Meteor Trails 44
Specular Reflection 45
Modeling of Meteor Radio Scatter 48
Underdense Trails 49
The Overdense Trail 49
Forward Scatter Radio Reflections 50
Setting Up a Meteor Scatter Radio Receiving Station 51
Choosing a Receiver 51
The Antenna 53
Choosing a Radio Channel 54
Observing Technique 54
Automating the Observations 55
How to Confirm If Your System Is Working Properly 56
The Annual Meteor Streams 57
Annual Meteor Calendar 57
Chapter 4: Beyond the Solar System 71
Brightness and Flux Density 71
Continuum Emission 73
Thermal Bremsstrahlung Spectrum 73
Cyclotron and Synchrotron Radiation 74
The Synchrotron Spectrum 76
Inverse Compton Scattering 78
Emission Line Radiation 78
The HI 21 cm Emission Line of Hydrogen 79
The 3 K Microwave Background 81
Pulsars 81
Chapter 5: Antennae 85
The Dipole 86
A Simple Dipole 89
A Folded Dipole 89
Inverted V Dipole 90
Large Loop Antennae 92
Yagi Beam Antenna 94
The Log Periodic Array 96
Circular Polarized Antennae 98
The Parabolic Reflector (“The Dish”) 99
Antenna Impedance Matching 104
Transmission Lines (Feeder Cables) 104
Parallel Open Lead 105
Coaxial Cables 105
Impedance Matching 106
Using Coaxial Cable as a Matching Unit 108
Matching Stubs 109
Matching Transmission Lines to Multiple Antennae 109
Baluns 111
Chapter 6: Setting Up a Radio Astronomy Station 113
Selecting a Site for the Receiving Station 113
Atmospheric Noise and Other Environmental Considerations 114
Antenna Mounting 115
Power Considerations 116
Chapter 7: Radio Hardware Theory 117
The Superheterodyne 117
Measurement Scales 121
The dBm Unit 122
The dBmV 122
The dBmV 122
Noise 122
Noise Factor, Fn 123
Noise Figure, NF 123
Noise Temperature, Te 124
Sensitivity and Selectivity 124
Image Rejection 125
Third Order Intercept Point, IP3 125
Chapter 8: Introduction to RF Electronics 127
Passive Electronic Components 127
The Resistor 127
Capacitors 130
Inductors 132
Ferrite Materials (FT) 133
Powered Iron Types (T) 134
Crystals and Resonators 136
Diodes 137
Active Components 138
Bipolar Transistors 138
Field Effect Transistors (FETs) 139
Power Supplies 139
AC and Radio Frequency Signals 140
The Tuned (Tank) Circuit 142
Series Resonance 142
Parallel Resonance 143
Q Factor 144
Coupling Decoupling and Blocking 144
Transistors as Amplifiers 145
Circuit Construction 146
Screening 148
Test Instruments and Tools 148
Basic Tool Kit 148
Building the Impedance Bridge 150
Constructing the Noise Source 153
The Step Attenuator 155
Using Your Newly Built Test Equipment 157
Measuring Antenna Impedance 157
Using the Noise Source to Test Amplifier Performance 158
Chapter 9: Building a Very Low Frequency Solar Flare Monitor 159
Construction of the Antenna 160
The Computer as a Receiver 162
Setting Up Spectrum Lab 162
Chapter 10: Microwave Radio Telescope Projects 168
Required Parts 168
The Dish 168
The LNB 169
Construction 171
Observing Projects 175
Drift Scan Solar Transit 175
Detecting the Moon 177
Determination of the Equation of Time 177
The Slowly Varying Component of the Sun 177
A Low Cost Microwave Interferometer 178
Chapter 11: Building a Jupiter Radio Telescope 184
The Dipole 184
The Dipole Array 185
The Loop Aerial 187
The Receiver 189
Chapter 12: Building a Broad Band Solar Radio Telescope 193
Background 193
Design Overview 194
Construction 195
The Second IF Stage 200
The IF Filter 202
The Logarithmic Amplifier 204
The Log Amp Detector Circuit 205
Antenna Choice 205
DIY Filter Designing 206
Converting to a Spectrometer 210
Chapter 13: Data Logging and Data Processing 211
The Logging Multimeter 211
More Data Loggers for the PC 212
The Home Brew Method 213
Radio Skypipe Software 215
The Controller Option 217
The Arduino Duemilanove 218
The PC Sound Card as a Data Capture Device 221
Appendix AFormulae in Radio Astronomy 224
Appendix B: Bibliography 229
Appendix C: Suppliers, Groups,and Societies 235
Appendix D: Glossary 238
Index 242