Basic NEC with Broadcast Applications (Hardcover)

Chapter 1 - The Array Adjustment Process (11pp) This chapter uses the concept of local and global minima to explain why the results of NEC2 computer modeling need not be exact to be beneficial. It also gives a preview of the analysis process. 1.1 The Nature of NEC21.2 The Directional Antenna Adjustment Process1.3 Local and Global Minima1.4 The Role of NEC21.5 Analysis Overview1.6 Additional NEC2 Benefits1.7 Software RequirementsChapter 2 ? NEC2 Fundamentals (27pp) This chapter covers the basic use of NEC2. It teaches how to write the input file, the types of input files, naming conventions, how to run bnec.exe and how to read and interpret the output file.2.1 The NEC2 Engine2.2 NEC2 Operation2.3 Creating the Input File2.3.1 Naming the files2.3.2 Data Commands2.3.3 Data Command Types2.3.4 An Input File Illustration2.3.5 Comment Commands2.3.6 Geometry Commands2.3.7 Program Control Commands2.4 Reading the Output File2.4.1 The Header2.4.2 Structure Specification2.4.3 Segmentation Data2.4.4 Data Lines, Frequency, Loading and Environment Data2.4.5 Antenna Input Parameters2.4.6 Currents and Locations2.4.7 Current Moments2.4.8 Power Budget2.4.9 Radiation Pattern2.5 Exercise 2Chapter 3 - Modeling the Radiator (20pp) This chapter covers the various NEC2 model configurations that can be used to represent the radiating tower, the rules that apply to modeling and exciting the tower. It also introduces a viewing program to verify tower coding.3.1 Modeling Guidelines3.2 Guideline Summary3.2.1 Modeling the Radiator3.2.2 Modeling the Voltage Source3.3 Tower Configurations3.3.1 Single Wire Configuration3.3.2 4-wire Configuration3.3.3 2-wire Configuration3.3.4 Lattice Configuration3.3.4.1 Coding the Lattice Configuration3.3.4.2 Simplified Lattice Model3.4 Viewing the Tower Configuration3.5 Exercise 3Chapter 4 ? Array Geometry (15pp) This chapter converts the coordinate system used by NEC2 to a system consistent with the coordinate system normally used by the broadcast community. In addition it teaches how a multi-tower array is modelled and establishes a notation for multi-tower arrays. 4.1 The Coordinate System4.2 Array Geometry ? An Example4.3 The Array Input File4.4 Exercise 4Chapter 5 ? Loads, Networks and Transmission Lines (15pp) This chapter tells how to create a lumped impedance load in a NEC2 wire segment. It also shows how to use non-radiating networks in NEC2 and how to calculate the Y-parameters for those networks plus it shows typical uses for networks. A similar treatment is given for transmission lines.5.1 Modeling Impedance Loads5.2 Modeling non-radiating networks5.2.1 Typical Networks5.2.2 Typical Network Applications5.2.3 General Guidelines for Networks5.3 Modeling Transmission Lines5.4 Network Output File Listing5.4.1 Network Description5.4.2 Network Source and Load Impedance 5.4.3 Network Input Parameters5.5 Exercise 5Chapter 6 ? Calculating Base Drive Voltages (25pp) This chapter teaches how to use post processing software to convert the broadcaster's field ratios to NEC2's base drive voltages to initiate the computer modeling process. 6.1 Direct and Induced Currents6.2 Current Moments6.3 The Development Concept6.3.1 Normalized Drive6.3.2 Full Power Drive6.3.3 Shunt Reactance and Networks6.4 Example ? A Three Tower Array6.4.1 Create a Unity Drive File6.4.2 Calculate Unity Current Moments6.4.2.1 Tower #1 Moments6.4.2.2 Tower #2 Moments6.4 2 3 Tower #3 Moments6.4.3 Solve for Normalized drive Voltages6.4.4 Determine Full Power drive Voltages6.5 Exercise 6Chapter 7 ? Applying the Output File Data (24pp) This chapter shows how to translate the information in the NEC2 output file to useful design parameters. It teaches how to confirm the validity of the calculations and how to apply the results. It also shows how to use the output file data to set the start-up parameters for a new array. 7.0 Overview7.1 Verify the Field Ratio7.2 Plot Far Field Radiation Pattern7.3 Detune Unused Towers7.3.1 Detuning by Base Loadiung7.3.1.1 Example ? Detuning by Base Loading7.3.1.2 Base Loading Input File Listing7.3.2 Detuning by Skirting7.3.2.1 Example ? Detuning by Skirting7.3.2.2 Input File Listing ? Detuning by Skirting7.4 Antenna Monitor Readings7.4.1 Optimum Height for Sample Loops7.4.2 Arbitrary Height for Sample Loops7.4.3 Base Current Samples7.5 Drive Point Impedance7.5.1 Drive Point Impedance When Using a Network7.6 Exercise 7Chapter 8 - Model by Measurement (10pp) This chapter helps the reader match the self impedance of a tower as calculated by NEC2 to a measured reference by showing how changes in the various tower parameters tend to influence the calculated self impedance.8.1 Objective8.2 Adjusting the Model8.2.1 Number of segments8.2.2 Tower Diameter8.2.3 Segment and Radius Taper8.2.4 Base Capacity8.2.5 Drive Segment Radius8.3 Exercise 8Chapter 9 ? Top Loaded and Skirted Towers (13pp) This chapter applies NEC2 to the design and use of a tower skirt when applied to top loading, current distribution control and folded monopole applications. 9.0 General Considerations9.1 Top Loading9.1.1 Estimating the Size of a Top Hat9.1.2 Determining the Degree of Top Loading9.2 Skirted Towers9.3 Folded MonopolesChapter 10 ? System Bandwidth Analysis (18pp) This chapter extends the application of NEC2 to include the system networks. The methods described view the various functional interfaces within the signal path and displays their impedance bandwidth characteristics. 10.1 Introduction10.2 System definition10.2.1 Tower Models10.2.2 Tower Base Drive Voltages10.3 Bandwidth Analysis10.3.1 Source Impedance of the Drive Voltage10.3.2 Intermediate Data10.3.2.1 Procedure for Calculating Intermediate Data10.3.2.2 Tower Base Impedance10.3.2.3 ATU Input Impedance10.3.2.4 Transmission Line Input Impedance10.3.2.5 Phasing Network Input Impedance10.3 2.6 Power Divider Input Impedance10.3.3 Total System Bandwidth10.3.3.1 The Common Point Network10.3.3.2 Radiation Bandwidth10.4 Bandwidth ConclusionsChapter 11 ? Case Studies (24pp) This chapter is used to show the assets and liabilities of a NEC2 analysis. It uses measured data to confirm that the results of a NEC2 analysis need not be exact to be beneficial.11.0 Comparative Data11.1 Case Study #1 3-tower Array11.1.1 Array description 3-tower Array11.1.2 Self Impedance 3-tower Array11.1.3 Antenna Monitor Reading 3-tower Array11.1.4 Array Data 3-tower Array11.1.5 Discussion 3-tower Array11.1.6 Nec2 Input File 3-tower Array11.2 Case Study #2 6-tower Array 11.2.1 Array description 6-tower Array11.2.2 Self Impedance 6-tower Array11.2.3 Antenna Monitor Reading 6-tower Array 11.2.4 Array Data 6-tower Array11.2.5 Discussion 6-tower Array11.2.6 Nec2 Input File 6-tower Array11.3 Case Study #3 6-tower Array Night Time11.3.1 Array description 6-tower Array Night Time11.3.2 Self Impedance 6-tower Array Night Time11.3.3 Antenna Monitor Reading 6-tower Array Night Time11.3.4 Array Data 6-tower Array Night Time11.3.5 Discussion 6-tower Array Night Time11.3.6 Nec2 Input File 6-tower Array Night Time11.4 Case Study #4 Tall Tower Array11.4.1 Array description Tall Tower 11.4.2 Self Impedance Tall Tower11.4.3 Antenna Monitor Reading Tall Tower11.4.4 Array Data Tall Tower11.4.5 Discussion Tall Tower11.4.6 Nec2 Input File Tall Tower Chapter 12 ? Supplemental Topics (16pp) This chapter adds a few topics that may not be absolutely necessary but in any event they are interesting and add some insight into the analysis. Moreover, they are topics that are not well documented elsewhere thus their presentation here fulfils an existing need. 12.0 Introduction12.1 Parallel Feeds ? Network Combiners12.2 New Structures ? The NX Command12.3 Numerical Green's Function12.4 Ground Screens12.4.1 The GN Command12.4.2 The GR Command12.5 Finite Ground12.5.1 Reflection Coefficient Approximation12.5.2 Sommerfeld/Norton ProcedureAppendix A ? NEC2 Input File Statements (71pp) This appendix is a full listing of all the NEC2 command statements and serves as a valuable reference to the beginner and professional alike.Appendix B ? Error Messages (9pp) This appendix references error number versus an explanation of the error along with suggestions for remedy.Appendix C - Software (11pp) This appendix is essentially a user's manual for the software included on the associated disc. It includes instructions for the NEC2 program (bnec.exe), the geometry viewing program (NVCOMP.exe), the pattern plotting program (WJGRAPS.EXE), the