Direction And Position Finding By Wireless

CONTENTS INTRODUCTION 1 CHAPTER I Directional Transmission for Economic Reasons. — Directive Transmission and Reception for Direction and Position Finding. — Comparison of Visual and Wireless Methods of Direction and Position Finding. — Limitations of Visual Method. — Propagation of Light and Wireless Waves. — Directive Wireless Reception. — Position Finding by Directive Reception. — Historical Notes on Directive and Directional Transmission and Reception. — Mirror Reflectors of Hertz and Marconi. — Screening Methods of Zenneck. — Screen Reflectors of S. G. Brown, Lee de Forest and others. — Horizontal, Inclined and Bent Aerials of Galliot, Kiebitz, Marconi, Braun, Zehnder and others. — Marconi Bent Aerial. — Spaced Aerials of S. G. Brown, Garcia, Lee de Forest, Blondel and J. Stone Stone. — Braun's Heart-shaped Polar Diagram of Reception by Three Spaced Aerials. — H. J. Round's Experiments on Heart-shaped Diagram of Reception using Combined Loop and Open aerials. — Later Progress. Systems of D.F. used during European War. — The Radiophare. — Bellini-Tosi Radiophare. — Telefunken Compass. — Beam Radiophare. — Robinson Directive Transmitter. CHAPTER II THE THEORY OF THE WIRELESS DIRECTION FINDER 12 Mental Picture of Wave Propagation. — Wavelength. — Frequency. — Continuous, Interrupted Continuous and Damped Waves. — How a Simple Vertical Aerial Receives. — Aerial Tuning. — Polar Co-Ordinates. — Polar Diagram of a Vertical Aerial. — Equation of Circle Diagram. — How a Frame Aerial Receives. — Polar Diagram of Frame Aerial or Figure Eight Diagram. — Equation of Figure Eight Diagram. — Maximum versus Minimum Signal Strength for D.F. — Systems of Direction Finding. — The Simple Rotating Frame D.F. and Inherent Defects of Frame Aerials for Directive Reception. — Vertical Component and Direct Reception. — Polar Diagram of Figure Eight Distorted by Vertical and Direct. — Reduction and Elimination of Vertical. — Grid Condenser or Compensator Method. — Earthed Mid Point of Coupling Coils. — The Shielded Transformer. — Elimination of Direct. — Displacement Current Effects. — Determination of Sense or Absolute Direction. — Cardiod, Heart-shaped or Apple Diagram of Reception. — Equation of Heart-shaped Polar Diagrams — The Heart-shape Circuit. — Phase Adjustment of Heart-shape with Tuned Aerials. — Reversal of Sense by Reversal of Coupling or Incorrect Phasing. — Robinson System. — Errors. — Direction Finding with the Robinson System. — Avoidance of 90° Ambiguity. — Marconi-Bellini-Tosi System. — Theory of Radiogoniometer. — Conditions for Accurate Working of M.-B.-T. System. — Phase Relation of Aerial Currents, Balancing, etc. — Symmetry of Aerials. — Symmetry of Radiogoniometer. — Mutual Inductance between Aerial Circuits. — Timed Aerial M.-B.-T. Circuit. — Aperiodic Aerial System. — Coupling Error of Tight Coupled Radiogoniometer. — Correction of Coupling Error. — Receiving Qualities of Aperiodic Aerials. — The Simple Aperiodic Aerial Circuit. — Aperiodic Aerial with Loose Coupled Intermediate Circuit. — Heart-shape Circuit with Resistance Phasing of the Open Aerial. — Complete Aperiodic Heart-shape Circuit. Aerial Current Phase Relations in Loose Coupled Aperiodic Aerial Heart-shape Circuit. — Radiogoniometer for Sense Determination. CHAPTER III VALVE AMPLIFIERS AND DETECTORS 68 The Crystal as a Rectifier. — Theory of Rectification. — The Thermionic Valve. — Valve as a Rectifier. — Three Electrode Valve. — Saturation. — Three Electrode Valve as a Rectifier. — Elimination of Interference by Saturation of Rectifier. — Valve as a Magnifier. — Reaction. — Heterodyne or Beat Reception of Continuous Waves. — The Heterodyne or Independent Local Oscillator. — Sensitiveness of Heterodyne Reception. — Necessity for Rectification before Note Magnification or Telephone Reception. — Valve as a Note Magnifier. — High Frequency Cascade Amplifiers. — Pure Resistance Amplifier. — Voltage Magnification of a Valve Circuit. — Magnification Constant. — Transformer Amplifiers. — Characteristics of Cascade Amplifiers. — Aperiodic Transformer Amplifier. CHAPTER IV MAPS 97 Earth. — Angular Latitude and Longitude. — Linear Latitude and the Nautical Mile. — Linear Longitude and the Geographical Mile. — Positions on Earth's Surface. — Great Circles. — Convergency. — Types of Maps. — Gnomonic Chart. — Gnomonic Graticule. — Retro-Azimuthal Chart. — Orthomorphic Cylindrical Projection or Mercator's Projection. — Distances on Mercator's Chart. — Comparison of Properties of Gnomonic and Mercator's Charts. — Rhumb Line. — Limitations of Mercator's Chart for D.F. — Correction of Azimuthal Errors in Mercator's Chart. — Half-Convergency. — Sign of Half-Convergency. — Line of Bearing. — British Ordnance Survey Maps. CHAPTER V POSITION FINDING 121 Methods of Position Finding by Directive Reception. — The Shore D.F. Station. — Position Line by Means of One Shore D.F. Station. — Cross Bearings by Means of Two Shore D.F. Stations. — Fix by Means of Two Associated Shore D.F. Stations. — General Procedure. — Extract from Admiralty "List of Lights W/T. D.F. Stations, etc." — Laying off Position Lines. — The "Cocked Hat." — Practical Examples of the Use of Gnomonic and Mercator's Charts on the Calibration of a D.F. Station. — Choice of Gnomonic Graticule. — Locating the D.F. and Transmitting Stations on the Graticule. — Use of Mercator's Chart. — Correction for Half -Con vergency. — Discrepancies in Calculated and Measured Bearings. — The Ship Direction Finding Station. — Relative and True Bearings. — Position Line from Bearing of One Station. — Position Line from Bearings of Stations "In Transit." — Fix by Cross Bearings on Two Stations. — Cross Bearings on Mercator's Chart. — The Station Pointer. — Cross Bearings on Gnomonic Chart. — Fix by Cross Bearings of Three Stations. — Allowance for Distance Moved by Ship Whilst Taking Cross Bearings. — Position Circle. — Angle Subtended at Ship by Two Shore Stations. — Intersecting Position Circles. — Angles Subtended at Ship by Three Shore Stations. — Special Case when Position Circles Coincide. — Running Fix by Bearings on Single Station. — Prevention of Collision. — Vessels in Distress. — Examples of Wireless Position F hiding -. — Example of a Fix by Cross Bearings on Long Distance Stations using a Nautical Chart. — Above Example using a Gnomonic Graticule. — Example of a Fix by Cross Bearings on Short Range Stations. CHAPTER VI NIGHT EFFECT AND OTHER FREAK PHENOMENA 161 Coast Refraction. — Symptoms of Night Effect. — Modern Theory of Night Effect. — Polarisation of Electro-magnetic Waves. — Wave having Vertical Angle of Incidence and its Effect upon Polar Diagram of Reception of Simple Frame Aerial. — Relation Between Direction of Rotation of Plane of Polarisation and Direction of Rotation of Apparent Bearing. — Ionisation of Air and the Heaviside Layer. — Direct Path and Reflected Path of Waves from Transmitter to Receiver. — Causes of Vertical Polarisation of Magnetic Field in Reflected Wave. — Form of Transmitting Aerial. — Effect of Earth's Magnetic Field. — Relative Phases of E.M.F.'s induced in a Receiving Frame by the Direct and Reflected Waves. — Phase Relations between Components of Reflected Wave. — Interference effect. — Summary of Night Effect Conditions. — Sunset Variations of Signal Strength and Bearing. — Experimental Confirmation of Theory of Night Effect. — Observations of 90° Error. — Frequency and Violence of Night Effects. — Mechanism of the 90° Error Phenomenon. — Graphical Representation of a Type of Night Effect. — Comparison of Theoretical and Experimental Graphs. — Direction Finding in Three Dimensions. — Common Types of Night Effect. — Land and Sea. — Marking and Spacing Wave Discrepancies. — Minimum Distance Between Transmitter and Receiver for Night Effect. — Spark and Continuous Waves Change of Note of a Spark Signal. — Elimination of Night Effect Errors in Bearings. — Horizontal Frame. — Spaced Vertical Aerials or "Open Frame." — Spaced and Opposed Frames of Franklin and Weagant. — Heart-shaped Diagram. — Graphical Representation of Heart-shaped Polar Diagram under Influence of Night Effect. — Comparison of Simple Frame and Heart-shape Circuit in Practice. — Value of Heart-shape Circuit in Detecting Presence of Night Effect. CHAPTER VII THE SHORE D.F. STATION 202 Choice of Site. — Fixing Geographical Position of Site. — Correct Orientation of Station or Aerial Systems. — Methods of Finding the Direction of True North. — Geographical Method using Theodolite and Map of District. — Prismatic Compass. — The Marconi-Bellini-Tosi Shore Installation. — Laying-out Site of M.-B.-T Station.-^ Aerial Systems, their Construction, Insulation and Method of Support. — Triangular Frames. — Construction of Aerial. — Leading-in of Aerials. — Transposition of Lead-In. — Position of Receiving Building. — Earth System. — Receiving Apparatus. — Radiogoniometers for Tuned and Aperiodic Aerials. — Points in Design of Radiogoniometer. — D.F. Wave-Meter and Timing Buzzer. — The Shielded Transformer. — Points in the Design of the Shielded Transformer. - Layout and Adjustment of Receiving Apparatus. — Tuned Aerial Circuit. — Lightning Arrester and Earthing Switch. — Wavemeter and Tuning Buzzer. — Aerial Disconnecting Switches. Wiring of Circuit. — Installation of Radiogoniometer. — Aerial Tuning Condensers. — Reception of Continuous Waves by Means of Separate Local Oscillator. — Tuning and Balancing. — To Check the Circuit for "Vertical;" "Direct" and "Mutual." - Direction Finding. — Swing Readings. — Aperiodic Aerial Circuit. — Differences in Installation of Aperiodic and Tuned Aerial Circuit. — Earthing of Receiving Apparatus. — Tuning. — Checking for Vertical, Direct and Mutual. — Direction Finding. — Sharpness of Minima and Aperiodic Aerial Circuit. — Aperiodic Aerial Loose-Coupled Intermediate Circuit Heart-shape Receiver. — Uses of Above Circuit. — Arrangement of Circuit. — Intermediate Circuit. — Open Aerial Circuit. — Adjustment. — Factors Producing Indefinite Minimum with Heart-shape Reception. — Switching for D.F., Sense and Stand-By. — A Shore Service Direction Finding Installation (Marconi). — Diagram of Connections. — Description of Component Units. — Calibration. — Plotting Error Curve. — Quadrantal Error. — Elimination of Quadrantal Error in M.-B.-T. System. — Precautions in Making Aerial Adjustments for Calibration. — Choke Method of Calibration. — Calibration by Reducing Area of One Frame. — Comparison of Wireless and Magnetic Compass Correction. — Multiplex Shore D.F. Station. CHAPTER VIII THE SHIP D.F. STATION 264 Choice of Site for Aerials. — Chart Room or Wireless Office for D.F. Receiver. — Aerial Systems and Methods of Support. — Centre Support for Temporary Aerials. — Construction and Insulation of Aerials. — Aerials of R.M.S.P. "Andes" and S.S. "Ballygally Head." — Leading-In of Aerials. — Transposed Lead-In. — Shielding. — Bulkheads. — Lead Covered Paper Cables. — Circuit Alterations Necessitated by Long Cables. — Aerial Transformers. — Mid-Point Connection. — Static Leak. — Parallel Connection of Calibrating Choke. — A Marine Direction Finding Installation (Marconi). — Diagram of Connections. — Description of Component Units. — Layout of Apparatus. — Adjustment of Apparatus and Calibration. — To Find Direction of Ship's. Head and Hence the True Bearing of a Transmitting Station from the D.F. Bearing. — Case I, when Ship is alongside a Quay. — Case II, when Ship is not alongside a Quay. — The Magnetic Compass. — Magnetic Variation and Deviation. — Total Compass Error. — Case III, when Ship is not alongside a Quay and Compass Error is Unknown. — Case IV, when Ship is at Anchor or Moored. — Calibration. — Calibrating on Signals from Known Transmitting Stations. — Calibration when Ship is at Anchor or Moored. — Calibration when Ship is Under Way. — Special Transmitters for Calibration. — Taking Bearings. — Gong Signalling from W/T Office to Bridge. — The D.F. and the Gyro Compass. CHAPTER IX. THE AIRCRAFT D.F. INSTALLATION 298 The Problem of Aircraft Navigation. — Errors in Bearings. — Magneto Noise. — Engine Noise. — Systems of Aircraft D.F. — Wing Coil System. — Drift. — Magnetic Compass. — Position Finding by Wing Coil System. — Robinson D.F. — Relative Sizes of Main and Auxiliary Coils. — Robinson D.F. Adapted to the Wing Coil System. — Marconi -Bellini -Tosi System. — An Aircraft D.F. Installation (Marconi). — Diagram of Connections. — Description of Component Units. — Testing and Calibration of the Aircraft D.F. — Method of Rigging Wing Coils and M.-B.-T. Aerials bn Aircraft. — M.-B.-T. Fore and Aft Aerial. — Double Turn Fore and Aft Aerial. — Precautions against Magneto Interference. — Screened Ignition. — Screened Sparking Plug. — Temporary or Additional Screening Measures. — Effects of Vibration. CHAPTER X FAULT CLEARING AND MAINTENANCE 316 Common Symptoms of Failure. — No Signals. — Test of Insulation of H.F. Cascade Amplifier. — Test for Continuity of H.F. Cascade Amplifier. — Signals Fall off Gradually in Strength. — Noises in Telephones. — Bearings of All Stations in Same Direction. — Figure Eight Minima not Opposite on Scale. No Directional Reception. — Bearings all Too High or Too Low. — Bearings Incorrect in Certain Directions Only. — More than Two Minima with Figure Eight Circuit. — Indefinite Minima with Figure Eight Reception. — Bearings Incorrect on Certain Wavelengths only. — Heart-shape Balance un stable. — Faults Due to Wrong Connections of M.-B.-T. Aerials to Radiogoniometer. — Practical Example of Wrong Connection of M.-B.-T. Aerials. CHAPTER XI NOTES ON FIELD AND NAUTICAL ASTRONOMY 323 Solar Observations. — Positions of Heavenly Bodies. — Declination. — Polar Distance. — Right Ascension. — Sidereal Time. — Apparent Time. — Mean Time. — Greenwich Mean Time. — Equation of Time. — Zenith Distance. — Azimuth. — Hour Angle. — Hour Angle and Difference of Longitude. — Timing of Observations. — Series of Problems with Examples Worked. Out; — To Calculate the Time of Apparent Noon at Place in Terms of G.M.T. or Local Standard Time. — To find Time of Apparent Noon at Place and Hence the Longitude by Observations of Equal Altitudes of the Sun. — To Find the Meridian Altitude of the Sim by Observation and Hence the Latitude. — To Find Approximate True North by Observation of the Sun's Meridian Passage. — To Find True North from the Sim's Azimuth. — To Find Compass Error from the Sun's Azimuth. — To Find the Azimuth and Zenith Distance (Calculation of Great Circle Angle and Distance). — To Find the Great Circle Angle (Alternative Method). — To Plot a Great Circle on a Mercator's Chart. — To Draw a Gnomonic Chart (Graticule). BIBLIOGRAPHY 350 INDEX 305 LIST OF ILLUSTRATIONS. Frontispiece. Half-Convergency Diagram. Fig. 1 Position Finding by Directive Reception at two Stations A and B. 2 The Marconi "Inverted L" Aerial. 3 The Telefunken Compass. 4 Measurement of Wavelength. 5 Types of Wave Trains. 6 Induction of Alternating E.M.F. in an Open Aerial by an Electro-magnetic Wave. 7 Diagram to Illustrate the Use of Polar Co-ordinates. 8 Polar Diagram of Open Aerial. 9 Frame Aerial in Position of Maximum Linkage with Magnetic Flux in a Wave. 10 Phase of Induced E.M.F. in Frame Aerial. 11 Variation of Linkage with Rotation of Frame. 12 Polar Curve of Simple Frame as found from Diagram of Fig. 11. 13 Theory of Cosine Diagram. 14 Theoretical Cosine or Figure Eight Diagram of Simple Frame. 15 Box Form Frame Aerial. 16 Pancake Form Frame Aerial. 17 Circuit of Simple Frame D.F. 18 Figure Eight Diagram Distorted by Vertical. 19 Cause of Vertical. 20 Figure Eight Diagram of Frame with Circle Diagram of Vertical. 21 Figure Eight Diagram distorted by "Out of Phase Vertical." 22 Earthed Midpoint of Aerial Coupling Coils. 23 The Shielded Transformer. 24 The Heart-shaped Diagram. 25 Addition of E.M.F.s by Couplings. 26 Heart-shaped Diagram by Tuned Open and Frame Aerials with Tuned Intermediate Circuit. 27 Method of Avoiding Separate Open Aerial. 28 Theory of Circuit for Tuned Heart-shaped Diagram. 29 The Robinson D.F. Circuit. 30 Theory of Robinson D.F. 31 Ambiguity of Robinson D.F. 32 The Marconi-Bellini-Tosi D.F. 33 Action of Radiogoniometer. 34 Theory of Radiogoniometer. 35 Circuit of Tuned M.-B.-T. D.F. 36 Circuit of "Aperiodic" M.-B.-T. D.F. 37 Transformer Action in Aperiodic M.-B.-T. D.F. 38 Theory of Coupling Error of Radiogoniometer. 39 Graph of Coupling Error of Radiogoniometer. 40 Compound Search Coil. 41 Aperiodic M.-B.-T. D.F. with Shielded Transformer. 42 Aperiodic M.-B.-T. D.F. with Loose Coupled Jigger. 43 Aperiodic Circuit for Heart-shaped Diagram. 44 Theory of Aperiodic Circuit for Heart-shaped Diagram. 45 Simplified Circuit for Heart-shaped Diagram as "Sense" Indicator. 46 Extended Theory of Aperiodic Circuit for Heart-shaped Diagram. 47 Oscillatory Circuit. 48 Oscillatory Circuit with Rectifier. 49 Characteristic Curve of Carborundum Crystal. 50 Circuit of Fig. 48 with addition of Potentiometer. 51 Theory of Rectification by Curvature of Characteristic. 52 Characteristic Curve of Fleming Valve. 53 Circuit of Fleming Valve Rectifier. 54 Use of Common Battery for Heating Filaments and Operating Potentiometer. 55 Circuit for obtaining Characteristic Curves of 3-Electrode Valves. 56 Characteristic Curve of 3-Electrode Valve. 57 Grid Volt-Plate Current Curves of Marconi V-24 Valve. 58 Section of 3-Electrode Valve. 59 Marconi V-24 Valve. 60 The 3-Electrode Valve as a Rectifier. 61 Saturation Method of Eliminating Interference. 62 Magnification and Rectification by 3- Electrode Valves. 63 Use of Reaction. 64 Beat Reception. 65 Circuit of Local Oscillator. 66 Increased Efficiency of Rectification due to Heterodyne Reception. 67 Two-Stage Note Amplifier. 68 Two-Stage Note Amplifier with Common Battery. 69 Tuned Cascade High Frequency Amplifier. 70 Theory of Resistance Amplifier. 71 Theory of Inductance Amplifier. 72 Cascade Amplifier. 73 Cascade Transformer Amplifier with Common Batteries. 74 Voltage Magnification Curves of Different Types of Amplifier. 75 The Hemispheres. 76 Latitude. 77 Longitude. 78 Great Circle, Illustrating Convergency. 79 Great Circle, Illustrating Convergency. 80 True Bearing. 81 Optical Principle of Gnomonic Projection. 82 Optical Principle of Gnomonic Projection. 83 Gnomonic Projection by Optical Means. 84 Zenithal Properties of Gnomonic Projection. 85 Gnomonic Chart with Point of Contact at the Pole. 86 Tangent Planes of a Series of Gnomonic Graticules. 87 Cylindrical Projection by Optical Means. 88 Development of Cylindrical Projection of Fig. 87. 89 Great Circle on Globe. 90 Great Circle oh Gnomonic Chart. 91 Discrepancy between Great Circle Bearing and Mercatorial (or Rhumb Line) Bearing. 92 Sign of Half-Convergency. 93 Change in True Bearing as A approaches B along Great Circle. 94 Change in True Bearing as A approaches B along Rhumb Line. 95 Line of Constant Bearing. 96 43° line of Bearing with respect to B. 97 Position Line from Single Shore D.F. 98 Fix from Two Shore D.F. Stations. 99 Degree of Accuracy of Wireless Fix. 100 Variation in Accuracy of Wireless Fix with Relative Position of Ship and D.F. stations. 101 increase in Accuracy of Wireless Fix due to third D.F. 102 A Method of Plotting, at the Control Station, a Wireless Fix from three D.F. stations. 103 Use of the Gnomonic Graticule in obtaining True Bearings of Transmitting Stations from a D.F. 104 Use of Mercator's Chart in obtaining True Bearing of a Transmitting Station from a D.F. 105 True Bearing of Transmitting Station P from Ship 0 is the Sum of the Bearing of the Ship's Course and the Wireless Bearing of P relative to the Ship's Course. 106 Position Line on Mercator's Chart from True Bearing of one Transmitting Station. 107 Position Line on Gnomonic Chart from True Bearing of one Transmitting Station. 108 Position Line from Transmitting Stations "In Transit." 109 Alternative case of Position Line from Transmitting Stations "in transit." 110 Suggested Method of Navigating Atlantic Flight by Transit Bearings on Terminal Transmitting Stations. 111 Fix by Cross Bearings, from Ship D.F., on two Transmitting Stations. 112 Plotting Fix by Cross Bearings on Mercator's Chart. 113 Plotting Fix by Cross Bearings on Gnomonic Chart. 114 A Method of Plotting Fix when an Interval of Time elapses tyetween taking Cross Bearings on two Transmitting Stations. 115 A Method of Plotting Fix when Intervals of Time elapse between taking Cross Bearings on three Transmitting Stations. 116 The Position Circle. 117 Geometry of the Position Circle. 118 Construction foir Finding Centre of a Position Circle. 119 Intersecting Position Circles. 120 Coincident Position Circles. 121 The Running Fix. 122 Long Range Wireless Fix using Mercator's Chart. 123 Long Range Wireless Fix using Gnomonic Graticule. 124 Short Range Wireless Fix when Time Elapses between taking Cross Bearings. 125 Wireless Fix by Cross Bearings using Station Pointer. 126 Analogy illustrating Refraction. 127 Effects of Coast Refraction. 128 Frame Aerial in Position of Maximum Magnetic Linkage for Horizontally Incident and Normally Polarised Wave. 129 Frame Aerial and Horizontally Incident, Obliquely Polarised Wave. 130 Obliquely Polarised Wave, resolved into Vertically and Horizontally Polarised Components. 131 Frame Aerial in Position of Maximum Magnetic Linkage for Normally Polarised Wave with a Vertical Angle of Incidence. 132 Frame Aerial in Position of Minimum Magnetic Linkage for Wave having a Vertical Angle of Incidence and Vertically Polarised Magnetic Force. 133 Frame Aerial in position of Maximum Magnetic Linkage for Wave as in Fig. 132. 134 Polar Diagram of Reception of Simple Frame for Wave with Vertically Polarised Magnetic Force. 135 Compare with Fig. 132. 136 Position of Zero Magnetic Linkage for Normally Polarised Wave with a Vertical Angle of Incidence. 137 Position of Zero Magnetic Linkage when Plane of Polarisation of Magnetic Force in Wave is in direction "d." 138 Position of Zero Magnetic Linkage when Plane of Polarisation of Magnetic Force in Wave is in direction "c." 139 Paths of Direct and Reflected Rays from Transmitter to Receiver. 140 Paths of Direct and Refracted Rays from Transmitter to Receiver. 141 Multiple Reflection of Indirect Ray. 142 Method by which Abnormally Polarised Wave H., radiated from Horizontal Portion of an Inverted L Aerial, may reach a D.F. Station by Reflection. 143 Phase Relation, at Transmitting and Receiving Station, as a Function of Distance between Stations and Wavelength. 144 Interference Effect between Direct and Reflected Waves. 145 Example of Extreme Variation in Apparent Bearing. 146 Alternative method of Plotting Graph of Fig. 145. 147 Illustrating the 90° Error Phenomenon as plotted in Figs. 145 and 146. 148 Alternative explanation of 90° Error. 149 Another example of Extreme Sunset Variations in Apparent Bearing. 150 Polar Diagrams of A, B and C Component Waves, using Figure Eight Reception. 151 Vector Diagram for Summation of A, B and C Component Waves. 152 Series of Theoretical Polar Diagrams illustrating the result of Night Effect on Figure Eight Reception. 153 Results of Fig. 152 plotted to show their resemblance to Figs. 145 and 149. 154 Suggested Device for obtaining Azimuth and Zenith Angles of a Source of Electro-magnetic Waves. 155 Adcock's Scheme for Elimination of Night Effect. 156 Franklin and Weagant Spaced and Opposed Frames for Elimination of Night Effect. 157 Polar Diagram of A, B and C Component Waves using Heart- shape Reception and when the Reflected Wave has a Vertical Angle of Incidence. 158 Reduction in Receiving Power of Vertical Aerial when Reflected Wave has a Large Vertical Angle of Incidence. 159 Series of Polar Diagrams as in Fig. 152, but using Heart-shape Reception. 160 Enlarge view of part of Fig. 159 (d). 161 Figure Eight and Heart-shaped Polar Diagrams under influence of Night Effect. Freehand sketches during actual Aural Reception. 162 Further sketches made during Aural Reception illustrating Assymmetry of Heart-shaped Diagram whilst Direction of Zero Reception remains correct. 163 Determination of the Direction of North from Bearings obtained from a Map. 164 Map of District (imaginary) shown in Fig. 163. 165 Triangular Aerials with Single Mast. 166 Triangular Aerials with Central Mast and Four Short Comer Masts. 167 Square Aerials with Four Masts. 168 Plan of M.-B.-T. Triangular Aerial System. 169 Proportions of Triangular Aerial. 170 Simple Method of Measuring off Wire for Triangular Aerials. 171 Masthead Arrangement of Triangular Aerials. 172 Method of Anchoring Triangular Aerial. 173 Short Lead-in for Tuned Aerials. 174 Long Lead-in showing Transposition. 175 Temporary Lead-in for Aperiodic Aerials. 176 Radiogoniometer for use with Tuned Aerials. 176a Field Coil Connections. 177 Radiogoniometer for use with Aperiodic Aerials. 178 D.F. Wavemeter and Tuning Buzzer. 179 Shielded Transformer with Tertiary Winding. 180 Connections of Double Range Shielded Transformer with Reaction Coupling (see Fig. 181). 181 Front view of Shielded Transformer (see Fig. 180). 182 Effect of Capacity of Transformer Windings. 183 Lay-out of Tuned Aerial Circuit. 184 (a) Two Degrees of "Vertical." (b) Twenty Degrees of Rotation. (c) Combination of (a) and (b). 185 Lay-out of Aperiodic Aerial Circuit. 186 Lay-out of Aperiodic Heart-shaped Diagram Circuit. 187 Distortion of Heart-shaped Diagram due to Too Great an E.M.F. induced by Vertical Aerial. 188 Distortion of Heart-shaped Diagram due to Too Great an E.M.F. induced by Loop Aerials. 189 Switching Circuit for (l) "D.F." (2) "Sense" and (3) "Stand By." 190 M.-B.-T. Shore Pattern D.F. Receiver (Marconi). 191 Circuit of D.F. Receiver Shown in Fig. 190. 192 Radiogoniometer. (See Fig. 190). 193 Intermediate Circuit Tuning Condenser. (See Fig. 190). 194 Transformer Panel. (See Fig. 190). 195 Jigger Condenser. (See Fig. 190). 196 Jigger Panel. (See Fig. 190). 197 H.F. Amplifier Control Panel. (See Fig. 190). 198 H.F. Amplifier. (See Fig. 190). 199 Double Note Magnifier. (See Fig. 190). 200 Error Curve of Uncalibrated D.F. 201 Distortion of Bearings of Uncalibrated D.F. 202 Methods of Reducing Temporarily, Area of M.-B.-T. Aerial. 203 Inverted Fore and Aft Loop. 204 Separated Loops. 205 Diamond-shaped Loop to Avoid Unbalance. 206 Fore and Aft Loop Between Funnels. 207 Aerial Lower Centre Support showing Junction Boxes for Leading-in Cables. 208 Temporary Installation; Aerial Lower Centre Support with Rubber Cable Lead-in. 2P9 Aerial Apex Insulator. 210 Corrugated Ebonite Insulator and Spring for Support of Outer Comers of Loops. 211 General View of D.F. Aerials of the R.M.S.P. "Andes." 212 D.F. Aerials of the S.S. "Ballygally Head." 213 Screened Lead-in. 214 Lead-Covered, Paper Insulated Twin Cable for Lead-in. 215 Interior of W/T Office, showing , Internal Junction Boxes. 216 Self-Capacity of Lead-Covered Twin Cable. 217 Arrangement of Ratio Transformers in Aerial and Lead-in* 218 M.-B.-T. Marine Pattern D.F. Receiver (Marconi). 219 Circuit of D.F. shown in Fig. 218. 220 Radiogoniometer. (See Fig. 218). 221 Variable Tuning Condenser. (See Fig. 218). 222 Transformer Panel. (See Fig. 218). 223 Amplifier Panel. (See Fig. 218). 224 Earthing Relay. (See Fig. 218). 225 Calibrating Chokes. (See Fig. 218). 226 Error Curve of Uncalibrated Ship D.F. Installation. 227 The Wing Coil Method ot D.F. 228 Swing Bearing using the Wing Coil. 229 Drift of Aeroplane due to Wind on Beam. 230 Effect of Drift when Flying Head-on to Transmitting Station Objective. 231 Robinson D.F. using Box Type Coils. 232 Robinson D.F. using Pancake Type Coils. Mounted in Fuselage of Handley- Page Aeroplane. 233 Combined Box and Pancake Type Coils used by U.S. Navy. 234 Robinson D.F. adapted to Wing Coil Method of D.F. 235 Circuit of M.-B.-T. Aircraft D.F. 236 M.-B.-T. Aircraft D.F. Installation (Marconi). 236a Key Diagram for Fig. 236. 237 Rigging of M.-B.-T. Fore and Aft Aerial on "Short" Flying Boat. 238 M.-B.-T. Fore and Aft Aerial Supported on Masts. (See Fig. 239). 239 View of Fore Mast used in Special Cases to support M.-B.-T. Fore and Aft Loop. 240 Method of Running Fore and Aft M.-B.-T. Loop to Clear Engine on Single Engine Machine. 241 "Tuned Stopper" Circuit for Elimination of Magneto Interference. 242 Rolls-Royce Engine fitted with Screened Ignition and Screened Sparking Plugs. 243 Screened Sparking Plug. 244 True Position and Geographical Position of Heavenly Bodies. 245 Movement of the Earth Round the Sun. 246 Azimuth, Zenith Distance and Hour Angle. 247 Contacts of Sun's Image with Cross Wire of Theodolite. 248 Latitude as a Function of Sun's Altitude. 249 Latitude as a Function of Sun's Altitude and Declination. 250 To find Direction of True North from the Sun's Meridian Passage. 251 Great Circle Angle and Distance by Calibration. 252 Calculation of Intersections of Great Circle AB with Meridians in order to Plot Great Circle on Mercator's Chart. 253 Construction of a Gnomonic Graticule. 254 Portion of Completed Graticule. Digitized by Google.
Includes bibliographical references (pages 356-363)
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