Antenna Modeling Notes: Volume 1, 2 & 3

Antenna Modeling Notes

~ Volumes 1, 2, 3 & 4 ~
1,600 Pages!!
Plus 330 Modeling Files (150 in .NEC/.EZ/.NWP Formats)
L. B. Cebik, W4RNL

Volume	Pages	Modeling Files
1	377	94
2	400	86
3	433	60
4	395	90
	1605	330

ABOUT THE AUTHOR:
Considered an expert on antennas, L. B. Cebik has written and published two other NEC tutorials and 15+ books on various technical subjects in the field with works on antennas for both the beginner and the advanced student. Among these books is a basic tutorial in the use of NEC antenna modeling software and compilations of his many shorter pieces. His articles have appeared in virtually every amateur radio publication, with translations of some into several languages. Retired Professor from the University of Tennessee at Knoxville, LB is Technical & Educational Advisor to the ARRL.

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 three 25-column units. 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. Volumes 2 & 3 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 three 25-column 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. As with other volumes, this one is well-illustrated.

ad3.jpg (14835 bytes) 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.

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.

.....and more to come!

Although the list of topics seems to grow more advanced and complete, the appearance is an illusion. Indeed, the topics carry us into the use of advanced programs using the NEC and MININEC cores. However, the command set is far too large for coverage even in 4 volumes. As well, good antenna simulations depend as much on the ingenuity of modelers as they do on simply knowing how to apply various commands. Hence, the list of techniques by which to improve our models may well be endless. Mastering antenna modeling software has a further dimension that this volume does not cover: the use of the software to educate ourselves on the capabilities of various types of antennas. If we add this dimension of the use of NEC and MININEC to further mastery of the command structures and additional modeling techniques, then we may fairly predict that the series is far from its final episode. Watch for Volume 5 to come!

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

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