Analytical Table of Contents
Chapter Title Page
Introduction 1
In these preliminary notes, you will become familiar with the basic purpose and
design of this book on antenna modeling with NEC. You will come to
understand why you should go through the exercises carefully with your
software as well as reading the principles and techniques portions of each
chapter. In addition, you will learn something about the author.
Part A Basic Modeling and Model Testing A-1
1 NEC-2 and NECWin Plus 1-1
This chapter will introduce antenna modeling and acquaint you with NEC-2
capabilities and limitations, as well as distinguishing NEC-2 from other NEC-type
calculation cores. In addition, you will become familiar with the capabilities of
NECWin Plus, the overall program which contains the NEC-2 core.
2 Modeling Preparations 2-1
The exercises in this chapter introduce ways of preparing for a modeling run that
go far to ensure sensible results. The use of simple paper forms help translate
a physical antenna design into the data needed by the program for its
calculations. The use of such forms is also the basis of good modeling records
keeping.
3 Basic Antenna Models 3-2
In a series of simple models, this chapter will acquaint you with basic concepts
used in modeling on both the input and output sides of the NEC-2 calculations.
The exercises in this chapter will familiarize you with the process of modeling
with NEC-2, including working with the input data, running models, and using
fundamental output data.
4 NEC Output Data 4-1
NEC-2 provides a wealth of output data in tabular form which your program can
display directly and also translate into other very useful forms. This chapter will
acquaint you with the process of gathering and interpreting some of the most
basic data involved in antenna evaluation.
5 Careful Model Construction 5-1
Since hasty and careless modeling usually produces questionable output data,
the exercises in this chapter will familiarize you with some basic guidelines for
developing reliable models. It will also demonstrate some of the pitfalls of
careless modeling in a series of comparative models.
6 Convergence Testing 6-1
In this set of exercises, you will become acquainted with convergence testing as
one (but not the only) mark of a reliable antenna model. You will earn the
rationale for convergence testing and then, through a series of hand-on
exercises, learn to perform the test and to evaluate the results.
7 Frequency Specification 7-1
The exercises in this chapter will develop an understanding of the importance
of careful frequency specification for models. The chapter will guide you from
one-frequency ("spot") modeling to various types of multi-frequency ("sweep")
modeling. The chapter will also introduce you to potentials and pitfalls in
frequency-scaling your models.
Chapter Title Page
Part B Common Modeling Techniques, Limitations, and Work-Arounds B-1
8 Source Types and Placement 8-1
The exercises in this chapter will focus upon types and placement of sources in
antenna models. We shall encounter both voltage and current sources--as well
as when each is best applied--along with single, split, and multiple sources. The
exercises will also show you how to ensure that a source is exactly where you
want it.
9 Tapered-Diameter Elements 9-1
NEC-2's inability to model accurately physical elements with a tapering diameter
has resulted in a standard work-around modeling method. These exercises will
familiarize you with the detailed terms of the limitation, the requirements for
correctly applying the substitute model, and limitations associated with the use
of the corrective.
10 Geometry Limitations 10-1
In this set of exercises, you will learn of some NEC-2 limitations for which there
are no direct work-arounds. Of equal importance, you will learn something of
the process by which such limitations are analyzed and evaluated in a small
series of detailed modeling tests.
11 Grounds and Applications 11-1
This exercise set will acquaint you with the many ground options (including the
no-ground or "free space" choice) available within NEC-2. In addition, you will
work with some of the primary applications of the grounds, in some cases
finding ways to speed your analysis or development work by making the most
optimal selection.
12 Resistive Loads 12-1
This chapter will explore resistive loads. Resistive loads may be distributed or
"spot" loads. Distributed loads, or the conductivity of the wire material, are
integral to all but theoretic antennas. Spot loads, with specific resistance values
and segment placement, will be useful in a variety of applications.
13 Reactive Loads 13-1
Reactive loads (which also include resistive components) are so commonplace
in antenna design that NEC-2 offers three distinct ways of incorporating them
in models. These exercises will familiarize you with some applications of
reactive loads and also the best techniques for modeling them in each
application.
14 Transmission Lines 14-1
The final major ingredient that we shall explore is NEC-2's transmission line
function. In addition to developing an understanding of how to implement
transmission lines within the program, we shall also look at ways of modeling
some of the major applications of transmission lines in various antenna
configurations.
Chapter Title Page
Part C Practical Antenna Modeling C-1
15 Monopoles and Ground Planes 15-1
In these exercises, you will become familiar with modeling techniques useful for
1/4wl and similar monopoles and their associated ground planes over perfect
ground and above real ground. In addition, you will learn some substitute
techniques for modeling ground planes that are below ground.
16 Vertically Polarized Antennas and Arrays 16-1
In these exercises, you will meet a wide variety of vertically polarized antennas
and arrays, ranging from the vertical dipole to 1wl loops of phased verticals to
directional vertical antenna systems. Some arrays will employ parasitic
techniques, while others will use phased elements.
17 Bi-directional Wire Arrays 17-1
Although less prominent than other types of antennas today, bi-directional wire
arrays occupy an important niche in MF and HF radio communications. In these
exercises, you will become acquainted with the modeling techniques necessary
to develop and analyze this diverse group of antennas, including the routine use
of transmission lines as part of the design.
18 Yagis 18-1
The Yagi antenna is among the most common and varied horizontally polarized
antenna design used from HF through UHF. In these exercises, you will
become acquainted with some of the characteristics of parasitical antenna
element modeling and operation. You will also work with multi-band Yagis and
with stacks.
19 Horizontal Parasitic and Phased Arrays 19-1
Horizontal directional arrays are not limited to Yagis. In this set of exercises,
you will encounter a variety of simple and complex horizontally polarized
antennas using either parasitical or phase-line arrangements. In fact, in at least
one case, the antenna will use both types of arrangements.
20 VHF/UHF Antennas 20-1
The VHF/UHF range (30-3,000 MHz) presents a diversity of modeling
challenges, ranging from very large arrays of "HF-type" antennas to special
purpose antennas. We shall survey a part of the assortment in order to become
acquainted with concerns unique to modeling the smaller physical elements in
varied applications.
21 Special Structures 21-1
In our final exercises, we shall encounter a medley of different physical and
electrical structures. Most will have only occasional application; others introduce
some advanced techniques; still others are simply odd but interesting. Their
sum is the knowledge that many modeling projects require as much ingenuity
as technical know-how.
Appendix Some Useful Data for Antenna Modelers App-1
The Appendices contain a potpourri of information useful to antenna modelers. You
should perhaps clip or key this appendix, since you are likely to refer often to the
data on these pages.
1. Conductivity and Permittivity of Common Ground Conditions
2. Conductivity and Resistivity of Common Materials Used in Antenna
Construction
3. Common Wire Gauges and Associated Diameters in Inches and in Millimeters
4. Some Common Frequency-Wavelength Relationships
5. Frequency Domains
6. Some Common Transmission Lines Values
7. Metric-English Conversion
8. List of Models in Order of Appearance
Index Ind-1
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