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 entry-level
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 NEC-2, but has
now expanded its scope to include NEC-4. 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 (NEC-Win 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. |
CENTER |
Antenna Modeling Notes: Volume 2 |
he second volume of Antenna Modeling Notes contains columns 26 through
50 of W4RNL's long-running 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 NEC-2 topics, this volume
introduces some of the features of NEC-4, which can now be licensed reasonably
inexpensively to non-commercial users. As
well, the volume includes a 4-part tutorial on modeling by equation and another 2-part
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), NEC-Win Plus (.NWP), and generic (.NEC) formats. As well, Cebik has included his NEC-Win 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. See Volume 3 below. |
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 long-running 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 (NEC-Win 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 low-end
commercial versions of NEC-2. We examine the
rudiments of the GC (Wire Segment Length and Radius Tapering), GH (Helix-Spiral
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 NEC-2 and NEC-4 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 frequency-nimble 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 wire-gridding, the use of wire-grid structures to simulate both simple and complex conductive surfaces. See Volume 4 now available. |
Antenna Modeling Notes: Volume 4 |
his
fourth volume of Antenna Modeling Notes contains columns 76 through 100 of W4RNL's
long-running 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), NEC-Win 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. See Volume 5 next now released. |
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
long-running 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 entry-level programs such as EZNEC. Others
require NEC-4 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 receiving-mode models. The NEC-2 and NEC-4 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 NEC-2 handle insulated wires in a way that is comparable to the IS command in NEC-4. 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 long-running 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 entry-level programs such as EZNEC. Others require NEC-4. 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 NEC-2 handle insulated wires in a way that is comparable to the IS command in NEC-4. 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 long-running 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 entry-level programs such as EZNEC. Others require NEC-4. 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 NEC-2 handle insulated wires in a way that is comparable to the IS command in NEC-4. 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! |
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: NEC-2 | 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 Mid-Element 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 Tri-Banders 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: Front-to-Back 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 AZ-EL 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 | Multiple-Feedpoint 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 NEC-Deck | 351 |
48 | Radiation Plots: Polar or Rectangle; Log or Linear | 366 |
49 | Traps | 380 |
50 | The NEC-4 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: Helix-Spiral Specification | 204 |
63 | GH and GM: The NEC-4 Versions | 226 |
64 | An Orientation to the NEC Output Files | 246 |
65 | The 1/2-Wavelength 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 | 4-8-16-Infinite Sided Loops | 325 |
70 | Refining Physical Transmission-Line Models | 341 |
71 | The Average Gain Test Revisited | 357 |
72 | The GX or Symmetry Geometry Input | 368 |
73 | Source-to-Feedline 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 NEC-2 Way | 124 |
84 | GA: Creating and Moving Arcs | 142 |
85 | Electrical Fields at a Power Level and Distance | 161 |
86 | NEC-2 Manual Sample Files | 176 |
87 | NEC-4 Manual Sample Files | 189 |
88 | EX and PT Commands | 206 |
89 | Archimedes & Log Spirals for the NEC-4 GH Command | 220 |
90 | An
Orientation to NEC Near Fields Part 1. NEC-2 Input Basics & Simple Outputs |
232 |
91 | An
Orientation to NEC Near Fields Part 2. Some Refinements and NEC-4 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 | S-N, 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 Un-Modelable | 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 Tapered-Diameter, Bent and Hatted Dipoles |
132 |
111 |
Dipoles: Variety & Modeling
Hazards Zigzag, Fold-Back 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 Transmission-Line 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 Work-Arounds | 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 R-X 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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