Antenna Modeling Notes
ABOUT THE AUTHOR: 
Antenna Modeling Notes: Volume 1 

ffective basic instruction
in the use of antenna modeling programs seem to call for more than just the entrylevel
manuals that accompanied modeling programs. Therefore, LB started writing on the subject
of antenna modeling pretty much as he began to master the programs himself. In 1998, he
began a series of monthly columns for antenneX, a series still active today. That
series originated with information useful to beginning modelers, but has grown in recent
times to address as well potentials, limitations, and techniques of interest to more
advanced modelers. It also began by focusing upon MININEC and especially NEC2, but has
now expanded its scope to include NEC4. The time has come to collect these columns into a more convenient form for the reader. There is just too much material for a single volume, so Cebik has broken the collection into a series of books. He reviewed the text and graphics for each column to ensure as much accuracy as he could muster. LB has also reviewed the sample models used in each column. That process permitted him to add something to these volumes that is not available in antenneX or at his own web site. The Appendix to each of these volumes contains a collection of antenna modeling files in three formats: .NEC (ASCII), .EZ (EZNEC), and .NWP (NECWin Plus). LB also revised the text to include a file name for the applicable model in the Appendix. Therefore, should you wish to do so, you will be able to read a column in front of your computer and to test for yourself the ideas involved. Volume 1 (with 377 pages) contains the first (updated) 25 columns in the series, along with 94 antenna models. The table of contents indicates the topics covered. Additional Volumes are now available too and described below along with their table of contents. 


Antenna Modeling Notes: Volume 2 

he second volume of Antenna Modeling Notes contains columns 26 through
50 of W4RNL's longrunning monthly contribution to antenneX (columns #1 through #25 appeared in Volume 1) As part of his commitment to education in the art
and science of antenna modeling for newer modelers, this collection of includes items of
interest to both the beginning and the advanced modeler.
While the first 25 columns dealt with MININEC and NEC2 topics, this volume
introduces some of the features of NEC4, which can now be licensed reasonably
inexpensively to noncommercial users. As
well, the volume includes a 4part tutorial on modeling by equation and another 2part
series on designing with modeling software. You
will find coverage of vertical antennas and their radial systems, information on polar and
rectangular plots, and much more. As in Volume 1, Cebik has added models to this volume, in fact, 86 of them. These models are referred to in the text, and you can run them while reading to further illustrate the points under consideration. Except for models that have no possible counterparts in other formats, each model comes in the EZNEC (.EZ), NECWin Plus (.NWP), and generic (.NEC) formats. As well, Cebik has included his NECWin Plus models for designing Moxon Rectangles and monoband quad beams as a bonus. Volume 2 contains 400+ pages of text, illustrated throughout with nearly 200 graphics and accompanied by the 86 antenna models. 



Antenna Modeling Notes: Volume 3 

his
third collection of antenna modeling notes continues the compilation of the series that LB
began in 1998 in antenneX. It contains 433 pages with episode numbers 51
through 75 of the longrunning series that is running even today. The time had come to
collect these columns into a more convenient form for the reader. There is just too much material for a single
volume, so LB has broken the collection into a series of books. LB reviewed the text and graphics for each column
to ensure as much accuracy as possible. The sample models used in each column have been
reviewed and updates as well. That process
permitted LB to add things to these volumes not available before. The Appendix to each of these volumes
contains a collection of 60 more antenna modeling files in three formats: .NEC (ASCII), .EZ (EZNEC), and .NWP (NECWin Plus). Therefore, should you wish to do so, you will be
able to read an episode in front of your computer and to test for yourself the ideas
involved. This volume includes a potpourri of basic
and advanced modeling techniques. At the
basic level, there is a collection of graphic charts enumerating many of the DOs and
DON'Ts o NEC modeling so that you may extract and keep handy a series of reminders as you
construct a model. As well, LB has revisited
a number of topics to expand the coverage and go a bit more deeply into detail. The episodes on the Average Gain Test (AGT) and
the overall contents of the NEC output file are examples. Several columns devote themselves to
comparisons between NEC and MININEC. There are
types of models in which one or the other modeling core is superior, and the columns
attempt to explore when you should use one or the other. The key limiting factors include
both geometry and ground calculation concerns. Although
NEC cores are highly uniform in performance, MININEC cores have undergone extensive
modification by software developers and are not equally capable over a variety of modeling
tasks. This volume also includes introductions to
the use of some of the geometry and command inputs that are not available on most lowend
commercial versions of NEC2. We examine the
rudiments of the GC (Wire Segment Length and Radius Tapering), GH (HelixSpiral
Specification), GM (Coordinate Transformation), and GX (Symmetry) geometry input cards, as
well as introduce the use of the commands related to the use of Numerical Green's Function
files. For some of these model inputs, there
are differences between the required NEC2 and NEC4 entries, and we explore some of those
differences. In addition to mastering the various commands, potentials, and limitations of the basic modeling cores, there are a number of fundamental modeling tips and techniques that can be useful in the construction of ever better models. Episodes appear in this series in response, normally, to questions of the author. In this volume, we look at the simulation of circular loops by using the required NEC straight wires. Also included is a discussion of using parallel sources in place of complex geometries when two or more wires come together to form a single source wire or segment. A perennial question is how to incorporate into a model frequencynimble complex impedance matching sections that physically apply directly to the source of an antenna: we look at a usable but not universal technique. We also explore a small bit of the territory called wiregridding, the use of wiregrid structures to simulate both simple and complex conductive surfaces. 



Antenna Modeling Notes: Volume 4 

his
fourth volume of Antenna Modeling Notes contains columns 76 through 100 of W4RNL's
longrunning monthly contribution to antenneX. (Columns #1 through #25 appeared
in Volume 1, columns 26 through 50 appeared in Volume 2, and columns 51 through 75
appeared in Volume 3.) The latest volume includes information for both beginning and more
advanced modelers. As in Volumes 1 through 3, Cebik has added models to this volume, in fact, over 90 of them. These models are referred to in the text, and you can run them while reading to further illustrate the points under consideration. Except for models that have no possible counterparts in other formats, each model comes in the EZNEC (.EZ), NECWin Plus (.NWP), and generic (.NEC) formats. Volume 4 contains 395 pages of text, illustrated throughout with nearly 200 graphics and accompanied by the antenna models. 



Antenna Modeling Notes: Volume 5 

his
collection of antenna modeling notes continues the compilation of the series
that I began in 1998 in antenneX. It contains numbers 101 through 117 of the
longrunning series that continues even today. The time came to collect
these columns into a more convenient form for the reader. There is just too
much material for a single volume, so the collection is broken into numerous
units. I have reviewed the text and graphics for each column to ensure as
much accuracy as I can muster. I have also reviewed the sample models used
in each column. That process permitted me to add something to these volumes
that is not available anywhere else. Some models require elements of the
command set not included in entrylevel programs such as EZNEC. Others
require NEC4 Along the way, we shall explore some basic NEC calculations, including electric fields at a distance. We shall also learn how to supplement NEC calculations by using its output data to arrive at circular gain. Finally, we shall explore the relationship between the EX command and the PT command for special receivingmode models. The NEC2 and NEC4 manuals provide fundamental collections of sample models designed to illustrate in the most compact way possible as many NEC features as possible. These models appear only in print form. In this volume, there are many program listings with the various command sets and input parameters. The adequacy of models is, as it should be, a continuing challenge. Therefore, we shall revisit the convergence test with particular reference to its use with NEC. In addition, we shall take a look at some of the correctives that we use to work around some of the core's limitations. However, finding limitations and faults is not our goal. Rather, the goal is to make effective use of the program. Toward that end, we shall look at a techniques that will let us in NEC2 handle insulated wires in a way that is comparable to the IS command in NEC4. We shall also examine the various ground calculation systems that appear in NEC (and MININEC) software. This Volume 5 contains 264 pages with illustrations, program listings and performance charts. 



Antenna Modeling Notes: Volume 6 

his collection of antenna modeling notes, containing 323 pages, continues the compilation of the series that I began in 1998 in antenneX. It contains numbers 118 through 132 of the longrunning series that continues even today. The time came to collect these columns into a more convenient form for the reader. There is just too much material for a single volume, so the collection is broken into numerous units. I have reviewed the text and graphics for each column to ensure as much accuracy as I can muster. I have also reviewed the sample models used in each column. That process permitted me to add something to these volumes that is not available anywhere else. Some models require elements of the command set not included in entrylevel programs such as EZNEC. Others require NEC4. The adequacy of models is, as it should be, a continuing challenge. Therefore, we shall revisit the convergence test with particular reference to its use with NEC. In addition, we shall take a look at some of the correctives that we use to work around some of the core's limitations. However, finding limitations and faults is not our goal. Rather, the goal is to make effective use of the program. Toward that end, we shall look at a techniques that will let us in NEC2 handle insulated wires in a way that is comparable to the IS command in NEC4. We shall also examine the various ground calculation systems that appear in NEC (and MININEC) software. Volume 6 contains 323 pages with illustrations, program listings and performance charts.


Volume 7 

his collection of antenna modeling notes, containing 322 pages, continues the compilation of the series that I began in 1998 in antenneX. It contains numbers 133 through 147 of the longrunning series of 12.25 years, and now comes to an end. We collect these columns into a more convenient form for the reader. There is just too much material for a single volume, so the collection is broken into numerous units. Before his death, LB reviewed the text and graphics for each column to ensure as much accuracy as could be mustered. He also reviewed the sample models used in each column. That process permitted LB to add something to these volumes that is not available anywhere else. Some models require elements of the command set not included in entrylevel programs such as EZNEC. Others require NEC4. The adequacy of models is, as it should be, a continuing challenge. Therefore, we shall revisit the convergence test with particular reference to its use with NEC. In addition, we shall take a look at some of the correctives that we use to work around some of the core's limitations. However, finding limitations and faults is not our goal. Rather, the goal is to make effective use of the program. Toward that end, we shall look at a techniques that will let us in NEC2 handle insulated wires in a way that is comparable to the IS command in NEC4. We shall also examine the various ground calculation systems that appear in NEC (and MININEC) software. This final Volume 7 contains 322 pages with illustrations, program listings and performance charts. Sadly, there will never be another volume like this by LB!

Index of the titles found in Volume 1 
Column  Title 
Page 
1  Converging Toward Excellence  9 
2  Under the Limits: MININEC (3.13)  23 
3  Within the Lines: NEC2  36 
4  A Good Start is Half the Trip  50 
5  Putting Sources Where You Can Find Them  63 
6  Modeling Loads: What Kind, How Much, and Where?  74 
7  Maximizing Your Data  88 
8  Modeling Wire Arrays  106 
9  Modeling Ground Planes  120 
10  Tapering to Perfection  134 
11  A Ground is Just a Ground—Unless it is a Model of a Ground  147 
12  Verticals At and Over Ground  161 
13  Notes
on Reactive Antenna Loads and Their NEC Models A. Some Center Loading Basics 
179 
14  Notes
on Reactive Antenna Loads and Their NEC Models B. Some MidElement Loading Basics 
195 
15  Notes
on Reactive Antenna Loads and Their NEC Models C. Some Linear Loading Basics 
213 
16  Notes
on Reactive Antenna Loads and Their NEC Models D. Some Solenoid Loading Basics 
237 
17  Notes
on Reactive Antenna Loads and Their NEC Models E. Some Unfinished Business on Modeling Loads 
255 
18  Why TriBanders Are Hard to Model  269 
19  What Can We Learn From Tables?  281 
20  The Average Gain Test  296 
21  The NEC TL Facility  308 
22  Modeling Physical Transmission Lines  320 
23  Modeling LPDAs  338 
24  The Power and the Source  350 
25  Bringing Up the Rear: FronttoBack Ratios  362 
***  Appendix: Antenna Models  375 
Index of the titles found in Volume 2 
Column  Title 
Page 
26  The Scales of Equivalence  9 
27  Modeling by Equations: A. A Beginning  21 
28  Modeling by Equations: B. Bigger and Better Things  36 
29  Modeling by Equations: C. Formulas and Blocks  57 
30  Modeling by Equations: D. Scratch Pads & Coordinates  79 
31  A Case Study: A 90' Wire  95 
32  A Case Study: Rotating a Beam  109 
33  A Clean Sweep  125 
34  The Second Ground Medium  141 
35  Notes on Using AZEL Plots Effectively  161 
36  Getting a Grip on AZ/EL and Phi/Theta  179 
37  Verticals: Using the MININEC Ground  199 
38  Radials: Segmentation and Convergence  216 
39  Radials: Complex Radial Systems  230 
40  Resolution  244 
41  MultipleFeedpoint Loop Modeling  262 
42  Moving and Rotating  276 
43  Modeling Element Substitutes  292 
44  Designing With NEC: A Case Study Part 1: The 4Ss  308 
45  Designing With NEC: A Case Study Part 2: Evaluation & Reality  323 
46  A Load in Parallel With a Source  337 
47  So You Want to Read a NECDeck  351 
48  Radiation Plots: Polar or Rectangle; Log or Linear  366 
49  Traps  380 
50  The NEC4 IS Card: Insulated Wires  391 
***  Appendix: Antenna Models  406 
Index of the titles found in Volume 3 
Column  Title 
Page 
51  Testing the Fringes of Modeling Programs  9 
52  Flipping Among NEC Programs  24 
53  Voltage and Current Sources: How?  44 
54  GC: Wire Segment Length and Radius Tapering  58 
55  Parallel Sources, Angular Junctions & Avg Gain: Correcting Weaknesses  72 
56  When is MININEC Superior to NEC?  92 
57  Some Comments on Comments  107 
58  Some Basic Guideline Graphics for NEC  120 
59  MININEC and NEC: A Design Case Study  135 
60  NVIS Antenna Models and the Ground Type  154 
61  GM: Coordinate Transformation  176 
62  GH: HelixSpiral Specification  204 
63  GH and GM: The NEC4 Versions  226 
64  An Orientation to the NEC Output Files  246 
65  The 1/2Wavelength Resonant Dipole as a Core Test Instrument  265 
66  The State of the Art?  282 
67  Wire Grids 1: Plane and Simple  294 
68  Wire Grids 2: Angular and Awkward  310 
69  4816Infinite Sided Loops  325 
70  Refining Physical TransmissionLine Models  341 
71  The Average Gain Test Revisited  357 
72  The GX or Symmetry Geometry Input  368 
73  SourcetoFeedline Matching Techniques  386 
74  Some Numerical Green's Function Rudiments  400 
75  NEC: Power Efficiency vs. Radiation Efficiency  416 
***  Appendix: Antenna Models  431 
Index of the titles found in Volume 4 
Column  Title 
Page 
76  Developing
Antenna Expectations Using Modeling Software 1A: Horizontal Wires in the Lower to Medium HF Range 
9 
77  Developing
Antenna Expectations Using Modeling Software 1B: Horizontal Wires in the Lower to Medium HF Range 
23 
78  Developing
Antenna Expectations Using Modeling Software 2A: Vertical Dipoles 
40 
79  Developing
Antenna Expectations Using Modeling Software 2B: Vertical Monopoles 
63 
80  Developing
Antenna Expectations Using Modeling Software 2C: Vertical Monopoles 
82 
81  Appreciating the EK Command  100 
82  The Nature and Adequacy of NEC Correctives  113 
83  Insulated Wires: The NEC2 Way  124 
84  GA: Creating and Moving Arcs  142 
85  Electrical Fields at a Power Level and Distance  161 
86  NEC2 Manual Sample Files  176 
87  NEC4 Manual Sample Files  189 
88  EX and PT Commands  206 
89  Archimedes & Log Spirals for the NEC4 GH Command  220 
90  An
Orientation to NEC Near Fields Part 1. NEC2 Input Basics & Simple Outputs 
232 
91  An
Orientation to NEC Near Fields Part 2. Some Refinements and NEC4 Additions 
250 
92  Calculating Circular Gain  263 
93  Convergence Revisited  274 
94  GR: The “Generate Cylindrical Structure” Command  286 
95  Some Basics of the NT Command  298 
96  Some Further Applications of the NT Command  314 
97  Integrating Commands: A Case Study  332 
98  Planar Reflectors: Wire Grid vs. SM Patches  346 
99  SN, RCA, and MININEC Grounds  362 
100  The Dipole and the Coax  377 
***  Appendix: Antenna Models  393 
Index of the titles found in Volume 5 
Column  Title 
Page 
101  Modeling the UnModelable  7 
102  True Azimuth Models – NSI Software  22 
103  True Azimuth Models – EZNEC Software  36 
104  PS: I Change  50 
105  Models, Symmetry and Loads: A Couple of Reminders  62 
106  Refining Our Notions of Azimuth Patterns  79 
107  Scaling Models  91 
108  Dipoles: Variety & Modeling Hazards Linear, V & Folded Dipoles in NEC  104 
109 
Dipoles: Variety & Modeling
Hazards Linear, V & Folded Dipoles in MININEC 
117 
110 
Dipoles: Variety & Modeling
Hazards TaperedDiameter, Bent and Hatted Dipoles 
132 
111 
Dipoles: Variety & Modeling
Hazards Zigzag, FoldBack and Fan Dipoles 
148 
112  Wires Meeting Ground: 2 Cases  165 
113  When Simple Geometries Become Complex: A Rhombic Study  182 
114  Modeling Folded Monopoles  201 
115  Single, Bifilar and Quadrifilar Helices  221 
116  Insulation Revisited  240 
117  Modeling and the Logic of Question Resolution  252 
Other Publications  264  
Index of the titles found in Volume 6 
Column  Title 
Page 
118  Modeling Odd Structures: the Gamma Match I  7 
119  Modeling Odd Structures: the Gamma Match II  24 
120  Back on the Ground  43 
121  Radiation Patterns and Propagation  60 
122  Reciprocity: Home on the Range  80 
123  Radiating and TransmissionLine Currents  109 
124  Modeling (with) Parabolic Reflectors  135 
125  When to Worry and When to Not: a Case Study  155 
126  "Ideal" Polar Plots  171 
127  A Potpourri of Modeler Miscellanea  193 
128  When Not to Use NEC for Antenna Modeling  216 
129  Some Rudiments of Receiving Pattern Modeling  234 
130  Models vs. Prototypes  256 
131  AM BC Modeling with NEC I  278 
132  AM BC Modeling with NEC II  298 
Other Publications  323  
Index of the titles found in Volume 7 
Column  Title 
Page 
133  AM BC Modeling with NEC III  7 
134  AM BC Modeling with NEC IV  25 
135  AM BC Modeling with NEC V  41 
136  AM BC Modeling with NEC VI  70 
137  NEC Implementations, Cores, Limits and WorkArounds  87 
138  Types of Substitute Models  103 
139  Antenna Matching with EZNEC Version 5: Part 1  125 
140  Antenna Matching with EZNEC Version 5: Part 2  148 
141  Circular RX Graphs  171 
142  VOACAP Type 13 Files  193 
143  Modeling Radiating Surfaces  217 
144  Receiving Directivity  243 
145  Serial Feedline Connections  259 
146  Unequal Serial Feedline Connections  281 
147  Warnings and Errors of NEC & What to Do  302 
Other Publications  322  
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