4NEC2 Definitive Guide
4NEC2 Definitive Guide
Mark Schoonover KA6WKE
Buy on Leanpub

Table of Contents


Thanks for downloading and reading this Definitive Guide to the widely popular 4NEC2 Antenna Modeling software. 4NEC2 is a NEC based antenna modeler and optimizer developed by Arie Voors. This is a 3rd party book and is not connected to Arie Voors in any way. If you find mistakes in this book, they are all mine. :)

The sample version of the book is complete but the full version is in progress. As chapters or appendices are completed, they will be released as updates. All updates for the sample and full version of this book are FREE, and it’s available in PDF, ePUB, and MOBI formats.

The full version of the book starts with chapter 4 that covers the different 4NEC2 editors. The Geometry Editor, due to it’s complexities, warrants its own chapter. Other chapters will include using the optimizer and matching tools, using gnuplot for high resolution graphs, using ItsHF and VOACAP, with the remaining chapters on design and analysis of various kinds of antennas such as verticals, multi-element, loops, satellite, and a grab bag of antennas the author finds interesting.

If you’d like to give feedback, please do via Leanpub 4NEC2 Definitive Guide feedback page.


Selecting Menus

Directions to which menu to use is shown as Edit->Copy where the menu is left of the -> and the menu option is to the right of the ->. Sub-menus are shown as Run->Quickly->possible. Both menus and their options matches what is shown in the program.

Program Specific Text

Program specific text IE: menu text and screen output, etc will look like this Program Specific Text a fixed monospaced font.

Warnings, Tips, Errors, Information

PC Requirements

Just about all computers of recent vintage can run 4NEC2 without issues. Obviously the more memory and CPU speed you have the faster the analysis will go and the more complex of an antenna that can be analyzed.

Supported Operating Systems

Basic functionality was tested on the following operating systems.

  • Windows 7 64bit
  • Windows 8 64bit
  • Windows 10 64bit

About the Author

Mark Schoonover has been licensed since 1982 when he got his Novice license on a wager with his dad. If he didn’t pass his Novice test, he had to mow the lawn for FREE all summer break. He got his General license in 1983 from the now long closed FCC Field Office in San Francisco. Upon his return from Navy active duty in 1987 he got his Advanced license. Around 2000 he got his Extra. He’s held his call since 1982 and doesn’t have any plans to obtain a vanity call. He enjoys long distance cycling, hiking, homebrewing and contesting from his pip-squeak station located in Arizona.

Professionally, he has a degree in Computer Science and Software Engineering. He switched from Electrical Engineering when the internet became publicly available. Currently he’s an IT Solutions Architect for a major health care provider in the United States.

Chapter One - Installation

Downloading and installing 4NEC2 will be covered in this chapter. Installation is straight forward and the default settings will be used throughout this book for all screen captures. The author is using Windows 10 64bit for this book. Screens in other operating systems may look slightly different but otherwise 4NEC2 will function identically.

Downloading 4NEC2

4NEC2 can be downloaded from http://www.qsl.net/4nec2/. This book will cover version 5.9.2 released in March 2021 and will be updated as new versions of 4NEC2 mecome available. There are several different files available to download. For this book, you’ll need to download 4nec2(setup.exe) from the left menu. If you don’t see the download menu section, scroll down. Simply right-click on 4nec2(setup.exe) and save it to your desktop or downloads folder. 4NEC2 can be installed from any directory.

Installing 4NEC2 and Configuration

Extract 4NEC2 by right-clicking on the 4nec2.zip file and select Extract All from the flyout menu. Double-click on the 4nec2 folder that was created, then double-click again on the Setup4nec2.exe file. The following window will appear:

4NEC2 Opening Screen
4NEC2 Opening Screen

Click Next to continue and Next again to accept the default installation directory.

4NEC2 Default Installation Directory
4NEC2 Default Installation Directory

The Start Menu window will be displayed:

Add to the Windows Start Menu
Add to the Windows Start Menu

Click Next to continue. The create desktop icon window will be displayed:

Create 4NEC2 Desktop Icon
Create 4NEC2 Desktop Icon

Click Next to continue. The Ready to Install window will be displayed:

4NEC2 Ready to Install Confirmation
4NEC2 Ready to Install Confirmation

Click the Install button to start installation. Watch the little green bar!

4NEC2 Installing
4NEC2 Installing

The next window to appear will be how to find the getting started and README files:

4NEC2 Getting Started & README Files
4NEC2 Getting Started & README Files

Click Next to continue. The Installation Completed window will appear:

4NEC2 Installation Completed!
4NEC2 Installation Completed!

Click Finish to continue. You should have the 4NEC2 Main Window, 4NEC2 Geometry Window, and the _ReadMeFirst.txt file displayed. Read through the README file, it contains the latest information about this version of 4NEC2.

4NEC2 Installed
4NEC2 Installed

On the desktop, there should be three new icons.

4NEC2 Desktop Icons
4NEC2 Desktop Icons

Additional 4NEC2 information is located in C:\4nec2\ directory. The _GettingStarted.txt file may be slightly out of date but feel free to use as needed. This completes the default 4NEC2 installation.

Chapter Two - Learning Your Way Around

Let’s work our way through the 4NEC2 user interface. Double-click on the 4nec2 desktop icon:

4NEC2 Desktop Icon
4NEC2 Desktop Icon

to launch the program. When first started, 4NEC2 will display two windows, the Main Window, and the Geometry Window. Keep the Help File in mind as well.

Finding Help

4NEC2 comes with context sensitive Help. To access Help, at the point you want additional information, press the F1 key. From the 4NEC2 website, there’s also a forum dedicated to the software and can be found at the 4NEC2 forums.

General antenna discussions can be found on the eHAM.net antenna forum and the QRZ.com antenna forum as well.

There is a Groups.IO mailing list dedicated to this book. It’s a closed group for discussing the book, asking for clarifications, or taking the author to task for an egregious error! To subscribe, go to https://groups.io/g/4nec2defguide

The main source of announcements for this book are from Leanpub and Groups.IO.

Help Menu
Help Menu
4NEC2 Main Help Screen
4NEC2 Main Help Screen

Main Window

4NEC2 Main Window
4NEC2 Main Window


File Menu
File Menu
Open 4nec2 in/out file
Used to open existing 4NEC2 input or output files.
Save Output file as
Save current open 4NEC2 file to another filename.
Import Far-Field Data
Far-Field Data is used by HF propagation prediction software.
Print 4NEC2 project to your printer.
Exit | ESC | CTRL + S
Quit 4NEC2.

Below the Exit menu option is the most recently used file list.

Edit Menu
Edit Menu
Input (.nec) file
Displays the 4NEC2 Graphical User Interface (GUI) window where the antenna to be modeled is entered.
Output (.out) file
Uses the default text editor to display the 4NEC2 output file.
Settings Menu
Settings Menu
Notepad Edit | NEC editor/Geometry edit | NEC editor (new)
Sets the default editor for *.nec files. The default is NEC editor (new) but the Geometry Editor will be mostly used in this book. The other editors will be discussed in the full version of this book.
Auto segmentation
When checked allows long segments to automatically be broken into sub-segments. Default is 20 segments per halfwave length.
Stepped radius corr.
Option not available.
Input Power
Input power in Watts used to calculate voltages and currents in the near field.
Characteristic impedance of the system in Ohms. Normally 50 Ohms.
Pre-defined Frequencies
Opens the default editor where frequencies are added for frequency sweeping.
Pre-defined Symbols
Constants for Pi and wire sizes. Additional constants can be added to the Freq.txt1 file.
Show Circular-Polar
Changes the display to show circular or polar coordinate system.
Phi/azim unit | Length unit | Radius unit
Changes the units for azimuth as Phi/Theta, circular or CCW azimuth, length in meters/feet, or radius in mm/inches (AWG) of wire elements.

The next group of settings should rarely be used and will be left at their defaults for this book.

NEC Engine
Which NEC engine to use. There are several but we’ll be using the default Nec2dXS*.exe.
Memory Usage
Optimize memory usage for number of field points, number of sweep steps, EX/LD/TL Cards2, number of SYmbols, 3D points, and patches.
Optimizer | ItsHF Settings | Other Settings
Additional analysis and 3rd party programs configuration.
Calculate Menu
Calculate Menu
NEC output-data
Displays the Generate output data screen.
NEC Output Data
NEC Output Data

The sample version of this book will use the Far Field pattern option to generate NEC output data. Go to Edit->Output (.out) file to view the generated output file in the configured default editor.


Opens different 4NEC2 program windows & viewers.

Window Menu
Window Menu
Context Sensitive Help
F1 -> Opens the Main Help file.
F2 -> opens the Main 4NEC2 program window.
F3 -> opens the Geometry window.

The Geometry window is detailed in the Geometry Window section.

F4 -> opens the Pattern window

The Pattern window is detailed in the Pattern Window section.

Line Chart
F5 -> Opens the Gain/SWR/Impedance window.
3D Viewer
F9 -> Start/select 3D-viewer window.

The 3D Viewer is detailed in the 3D Viewer section.

Smith Chart
F11 -> View interactive Smith Chart

The Smith Chart is detailed in the Smith Chart section.

Show Menu
Show Menu
Excite/Load info
Displays calculated information in Rectangular Form by replacing the Environment section of the Main Window.
Excite/Load info
Excite/Load info
Polar Notation
Displays the calculated results in Polar Notation. Polar Notation can be displayed by clicking on the Polar checkbox above the Excitation/Load results.
Polar Notation
Polar Notation
Run Menu
Run Menu
Geometry Builder
Displays the Geometry Builder for building complex antenna and ground systems.
Geometry Builder
Geometry Builder

The Geometry Builder is detailed in the Geometry Builder section.

Picture Viewer
Displays plots saved in graphic format or plot files.
Picture Viewer
Picture Viewer
This menu section is covered in the ItsHF Chapter in the full version of this book.


Main Toolbar
Main Toolbar

Remainder of Main Window

4NEC2 Main Window
4NEC2 Main Window
Current NEC output file
Feedpoint voltage in complex form. Clicking on the Polar checkbox will display this calculation in polar notation.
Series feedpoint impedance.
Parallel Form
Equivalent parallel feedpoint impedance.
The Standing Wave Ratio at 50 ohms feedpoint impedance.
Overall antenna efficiency.
Actual radiation efficiency. This efficiency determines how much your antenna radiates as a percentage of input power.
RDF [ db ]
Antenna gain referenced an isotropic dipole.
The frequency the antenna was analyzed.
Calculated wavelength of the analyzed frequency.
Feedpoint current in complex form. Clicking on the Polar checkbox will display this calculation in polar notation.
Series comp.
Series component in microhenries.
Parallel comp.
Parallel component in microhenries.
Input power
The applied power in watts from the transmitter as measured at the feedpoint of the antenna.
Structure loss
Power in microwatts (10-6) that’s lost due to the materials used in the construction of the antenna.
Network loss
Power in microwatts (10-6) that’s lost due to the matching network at the antenna feedpoint.
Amount of power in watts that’s radiated by the antenna.
Large textbox that displays the type of environment the antenna is analyzed in. This information can change depending if the Loads checkbox is checked.
Additional information contained in the comment section of the NEC input file. This information can change depending if the Loads checkbox is checked.
The number of subsegments or patches the antenna has been divided into for analysis.
Pattern Lines
Number of lines calculated for all the segments.
Freq/Eval steps
Displays the number of frequency or evaluation steps. Analysis at a single frequency will display a 1. Analysis with frequency sweeps or multiple steps will display a number greater than 1.
Calculation time
Elapsed time 4NEC2 required to complete the antenna analysis.
Start/Stop - number of degrees in the vertical plane. (Elevation)
Count - total number of steps.
Step - how many degrees in each step.
Start/Stop - number of degrees in the horizontal plane. (Azimuth)
Count - total number of steps.
Step - how many degrees in each step.

Geometry Window


Show Menu

Geometry Show
Geometry Show
Input file | Output file
View antenna geometry based upon the input file data or the 4NEC2 calculated output file.
Wire numbers
Displays the number of wires in the antenna design.
Displays the Tag number of the wire. Each wire should have different Tag numbers.
Open ends
Displays red-filled circles on wire ends that are not attached to anything.
Junctions (>2)
Displays the number of junctions on the antenna.
Displays each segment between a set of empty circles that are the same color as the wire.
Struc/Wire load
Displays in a brown line the load on the wire or structure - IE tubing.
Near/Far field
Displays vertical (El) & horizontal (Az) antenna pattern lines.
Povray -> Export Structure | Povray -> Export Far-field
Only used in the Standard version of 4NEC2.

View Menu

Geometry View
Geometry View
Returns antenna geometry to the center of the screen and default view.
Fix rot-center
Fixes the center of rotation of the antenna. Makes it easier to rotate about a fixed point.
Zoom in | Zoom out | Shift left | Shift right | Shift up | Shift down
Zoom in and out of the geometry. Shifting moves the geometry around the Geometry Window.
Last NEC-input
Displays the NEC input data in raw form using the default text editor.
Auto-segm. log | Step-rad. log
Not available.
SYmbol conversion
Opens the symbol.log file in the default text editor for custom symbols and their definitions. This is discussed in Chapter 4, NEC Editors in the full version of this book.

Validate Menu

Geometry Validate
Geometry Validate
Run geometry check
Manually validate the geometry of the antenna.
Show geo-check
Displays the geometry check results log file.
Set Auto geo-check
Configures 4NEC2 to automatically check antenna geometry.
Run segment checks
Checks each segment for validity then displays the results from the Model.log file in the default text editor.
Show all seg-checks
Shows all the segment checks from the antenna geometry.
Segm. L(ength)
Validates segment length. Default in Meters.
Segm. R(adius)
Validates the segment radius. Default in Meters.
Segm. Len/Rad
Validates segment length and radius as a ratio.
Junc. L big/ L small
Junc. R big / R small
Junc. Len/Rad
Surface-patch area
Validates the patch area on antennas so designed.

Currents Menu

Geometry Currents
Geometry Currents
Current magnitude
Displays the magnitude of all the currents on the antenna in green lines.
Current Magnitudes
Current Magnitudes
Phase only
Displays current phases.
Displays both the current magnitude and phase on the antenna elements.
Current Magnitudes & Phases
Current Magnitudes & Phases
Current real
Displays the real component of the current on the antenna elements.
Current imaginary
Displays the imaginary component of the current on the antenna elements.
Magnitude as color
Displays a legend and current magnitude in different colors corresponding to current magnitudes.
Current Magnitudes
Current Magnitudes
Phase as color
Displays a color legend and phase in different colors corresponding to phase calculations.
Current Phase
Current Phase
Change orientation
Use traditional disp.
Removes the curves from the magnitude and phase displays.
Incr. Log-factor | Decr. log-factor
Increase or decrease the logarithmic calculation. Helps with very small magnitudes and phases by increasing or decreasing the height of the curves displaying current and phase magnitudes.
Current Magnitudes & Phases Log Factors
Current Magnitudes & Phases Log Factors
Next frequency | Prev frequency
Step through a frequency sweep to the Next or Previous frequency used in the calculations.

Far-field Menu

Displays the far field antenna pattern on the antenna geometry.

Next pattern | Previous pattern
Displays the next or previous Phi or Theta far field patterns.
Change grid
Rotates through vertical pattern, horizontal pattern, or both patterns.
Displays the grid in linear format or ARRL format.
Gain as color
Displays total gain in V/m with corresponding magnitude legend.
Gain as Color
Gain as Color
Displays phase magnitude in degree.
Phase as Color
Phase as Color
Axial Ratio
Displays the ratio in dB between electric fields that are ninety degrees to each other on a circularly polarized antenna.
Antenna Sense
Decrease lines | Increase lines
Decreases or increases the number of lines representing the far field antenna pattern.

Near-field Menu

Displays the Near field antenna pattern. This is covered in the Pattern Window section.

Wire Menu

Wire Menu
Wire Menu
Identify W/S | Identify Tag
Display a specific wire number, segment number, or tag number in the antenna geometry. The found wire/segment/tag will be displayed in a bright green color. A Wire/segment information box will be displayed showing relevant information on the specific segment.
Identify W/S/T
Identify W/S/T
Next | Previous
Steps to the Next or Previous wire/segment/tag numbers.
Set as center
Moves the found wire/segment/tag and moves it into the center of the Geometry Window.
Polar notation
Toggles between rectangular notation or polar notation in the Wire/Segment info box.

Plot Menu

Plot Menu
Plot Menu
Uses gnuplot to display magnitude plots of individual wires/segments/tags.
Uses gnuplot to display phase plots of individual wires/segments/tags.
Uses gnuplot to display real value plots of individual wires/segments/tags.
Uses gnuplot to display imaginary value plots of individual wires/segments/tags.

Pattern Window

Pattern Window
Pattern Window

Displays the vertical (El) and horizontal (Az) calculated patterns of the antenna under analysis.

Pattern Show
Pattern Show

Show Menu

Next pattern | Prev pattern
Step through each “slice” of the antenna pattern. Each “slice” is stepped through a number of calculated degrees of resolution around the pattern. Resolution is configured in the Generate Window.
Displays an indicator in magenta on the pattern. Click the mouse on a point on the pattern to view the calculated gain and Theta/Phi. The J key isn’t needed for this feature.
Pattern Indicator
Pattern Indicator
Switches to the Geometry Window.
Inc. struct-size | Dec. struct-size
Increases or decreases the size of the structure supporting the antenna.
Prints out the pattern. Best results obtained from a color printer.
Change colors
Changes the colors of the Major/Minor axis and traces. This book will use the default settings.
Pattern Change Colors
Pattern Change Colors

Far Field Menu

The far field of an antenna is the distance from the radiating element greater than 2 wavelengths (>2\(\lambda\)). This is the field responsible for long distance communications and of primary concern to radio amateurs.

Pattern Far field
Pattern Far field
Vertical plane
When selected, displays the pattern’s vertical trace in blue. When deselected displays the horizontal pattern, also in blue.
Show both hor/ver
Displays both horizontal and vertical patterns. Horizontal trace is red and vertical is blue.
Show Multi pattern
Displays all patterns: Horizontal, Vertical, and Total Gain. Horizontal trace is red, vertical is blue, and Total Gain is in green. Total Gain is the combination of both Horizontal and Vertical traces. When blue and red colors are combined the resultant color is green.
Show Bold lines
Thickens all trace lines. Easier on the eyes.
ARRL-style scale
Displays traces and grid in ARRL style.
Font Scaling
Increase/Decrease the size of the fonts on the grid. Doesn’t change legend font size.
Pattern Font Scaling
Pattern Font Scaling
Next Phi/Az slice | Prev Phi/Az slice
Step through vertical traces (blue) by the configured resolution. The “Show both hor/ver” must be selected.
Next The/El slice | Prev The/El slice
Step through horizontal traces (red) by the configured resolution. The “Show both hor/ver” must be selected.
No normalization
Default setting.
Normalize overall
Show the outer ring of the graph at zero (scale). All calculated values are then compared to this value.
Normalize each
High/low ranges
Increases/Decreases the scale of the graph.

Near Field Menu

The near field of an antenna is the distance from the radiating element out to a distance less than two wavelengths (<2\(\lambda\)). This area is critical to antenna performance and matching because if other metallic objects are within this area, they could act like unintentional antennas, causing a change in the magnetic field about the antenna. This change in magnetic field alters the overall impedance of the antenna impacting the match to the transmitter. By understanding the near field, you’ll have a much better understanding of how multi-element antennas work.

Pattern Near field
Pattern Near field

The near field calculations are vastly different than far field calculations. In order to calculate the near field, choose the Near Field radio button in the Generate window. Both the voltage field (E field) and magnetic field (H field) can be calculated.

Calculating the Near Field
Calculating the Near Field
Set max scale value
Change the maximum value for the left scale instead of using the 4NEC2 calculated maximum value.
Inc. log-factor | Decr. log-factor
Changes the scaling logarithmic factor. Displays a course to fine details of the E-field or H-field.
XY, XZ, or YZ plane
Displays the XY, XZ, or YZ planes.

XY plane fixes the Z plane and displays just the X and Y planes of the near-field.

XY Plane
XY Plane

XZ plane fixes the Y plane and displays just the X and Z planes of the near-field.

XZ Plane
XZ Plane

YZ plane fixes the Y plane and displays just the X and Z planes of the near-field.

YZ Plane
YZ Plane
Smooth line plot
Show MPE colors
Changes the display showing Maximum Permissible Exposure limits. Used for RF exposure limit calculations.
Next Z, Y, or X pos | Prev Z, Y, or X pos.
Clicking on the pattern displayed will show a cross-hair at the location of the mouse click. Using the arrow keys will move this cross-hair around the pattern.
Next/Prev X,Y,Z
Next/Prev X,Y,Z
Inc. line plot Y/Z pos. | Decr line plot Y/Z pos.
Increases or decreases the Y-axis and Z-axis on the line plot view of the near field pattern. Must be viewing the near field as a line plot.
Change to line plot
Changes near field pattern to display X, Y, Z values as a line plot.
Near Field Line Plot
Near Field Line Plot
Change to 2D view
Changes from line plot view to 2D view of the near field pattern.

Compare Menu

Pattern Compare
Pattern Compare
Add new pattern | Remove pattern
Allows the adding or removal of another antenna pattern from a previous calculation. This allows comparing antenna designs.

Transfer Menu

Pattern Import
Pattern Import
Imports Full or 3D data, multiple frequency vertical plane and horizontal plane, and OpenPF data files.
Exports OpenPF Full/3D and OpenPF 2D slice of an antenna pattern.
Pattern Export
Pattern Export

FFtab Menu

Elevat/Theta Slices
Exports individual elevation calculations for each slice of the pattern. Data is displayed in the default text editor.
Azimuth/Phi Slices
Exports individual azimuth calculations for each slice of the pattern. Data is displayed in the default text editor.

Plot Menu

Pattern Export
Pattern Export

The plot menu uses gnuplot to create very high quality graphs of the antenna pattern.

3D plot

Pattern 3D Plot
Pattern 3D Plot

2D chart

Pattern 2D Plot
Pattern 2D Plot

3D Viewer Window

Displays the pattern in three dimensions. Using the mouse, the pattern can be rotated through a full 360\(^\circ.\)

3D Viewer
3D Viewer

Right Toolbar

Frequency at which the calculations were performed.
The main axis of the antenna.
Theta & Phi
Displays the current values for Phi/Azimuth & Theta/Elevation as the antenna pattern is rotated.
Zooms into the antenna pattern. Can view the far-field area around the feed point.
View a specific segment or tag within the far-field area.
Resets the pattern to the center of the window.
Selects which segment to be the center of rotation.
Displays instructions on how to change the color settings. Use CTRL + Q
True Rad
Toggles between the true radius of the segments and relative radius of the elements.
Axis Checkbox
Hides the X, Y, and Z axis from the display.
Displays or hides the antenna structure under analysis.
Hide patt.
Displays or hides the antenna pattern under analysis.

Displays different far-field slices in 3D.

Displays the Vertical/Horizontal/Total Gain pattern including E fields of Phi and Theta.
Changes the quality of the pattern. Author didn’t notice any perceptible changes to the pattern moving the slider back and forth.

Smith Chart

Displays impedance and S-parameters on a Smith Chart.

Smith Chart
Smith Chart
Customize the Smith Chart; normalize the chart, change the grid density, display rectangular results, display and remove measurement points on the SWR circle, and print out the chart.
Smith Chart Show
Smith Chart Show
Increase/Decrease the frequency to be displayed on the Smith Chart and move closer/away from the generator or source.
Smith Chart View
Smith Chart View


Smith Chart Export
Smith Chart Export

Export Smith Chart data in Touchstone or GAM formats.


Smith Chart Import
Smith Chart Import

Import Smith Chart data in Touchstone or GAM formats.

Geometry Builder

The Geometry Builder is used to design complex antenna systems for analysis. Patch, Plan, Box, Cylinder, Parabola, Helix, and Spherical antennas can be designed and analyzed. See the Geometry Builder chapter in the full version of this book.

Geometry Builder
Geometry Builder

Chapter Three - Building and Analyzing a Dipole Antenna

We’ll start out by building and analyzing a 20M dipole antenna over real ground using the Geometry Editor. Other than a brief discussion on theoretical antennas and real antennas, this book will analyze antennas in the physical world at the author’s location.

A Word or Three about Theoretical VS Real Antennas

Isotropic Antenna

An isotropic antenna is a theoretical antenna that is located out in free space. Free space is away from earth and far away from any other physical body. It’s an antenna that doesn’t exist in reality yet it radiates equally in all directions because it’s a simple “point” in space; like the period at the end of this sentence. The sun would be a good analogy of an isotropic antenna. It’s in free space, it’s a point source, and light radiates equally in all directions as humans view it from earth. An isotropic antenna is used as a reference only antenna and has zero gain (0 dBi). It’s used as a reference of which to compare antennas and really has no other practical purpose in amateur radio.

Dipole in Free Space

A dipole antenna in free space is also a theoretical antenna but it does have some gain compared to an isotropic antenna: +2.12 dBi. This gain is measured perpendicular to the antenna around the azimuth only.

Dipole Antenna in Free Space
Dipole Antenna in Free Space

The shape of the dipole is flat from end-to-end and not bent in any direction.

Real Antenna

Real antennas are what we work with here on earth. They are made from physical materials that impact radiation patterns, they interact with the ground beneath them and for several wavelengths away from the antenna. When we analyze antennas using 4NEC2, the measurements are compared to an isotropic antenna. By subtracting 2.12 dBi from an isotropic antenna measurement, the resulting measurement will be compared to a dipole in free space.

Comments on Theoretical Antennas and Such

From an engineering stand-point, theoretical antennas are the standard by which real antennas are compared to. When discussing antennas with fellow hams, gain measurements will be assumed to be either isotropic or dipole in free space. What about the measurement at your location? Would comparing your real antenna to theoretical antennas be beneficial? I would say yes and no. Yes when discussing with your ham buddies but when it comes right down to it, we’re only interested in the gain of real antennas at our physical location. If you’d like to know what the gain of your antenna is at your location, model a dipole antenna at the same height, ground type, and materials your antenna of interest will be made of. Analyze your new antenna design then compare the two. With this approach, you’ll have real world antenna measurements at your exact location. This approach might make more sense to you, but it wouldn’t make sense to other hams because they won’t understand a reference dipole at your location.

You’ll also find “claimed” antenna gain measurements in many radio related magazine ads, articles, and books. Now that you have an understanding of theoretical antennas, the units of gain in the ads/articles/books should either be dBi or dBd. If the units are simply dB, be VERY WARY of the manufacturers’ gain claims! Antenna gain is always compared to another antenna, be it isotropic or a dipole in free space.

Using the Geometry Editor

Getting Ready

Select the Geometry Editor from the Main Window as the default editor: Settings->Geometry edit. If you need to work with Imperial Units instead of Metric, it can also be changed from the Main Window: Settings->Length unit->Feet and Settings->Radius Unit->Inch/AWG

Creating a New NEC File

On the Main Window, click on the Geometry Editor toolbar button to display the Geometry Editor window. From the Geometry Editor File->New will create an empty editor. Create a new file name to save your work via File->Save. Name the file 20MDipole.nec and save it in a working directory outside of the antenna examples directories.

Design Conventions

Antennas exist in three dimensions in the real world which are easy enough to see. Drawing in three dimensions on a two dimensional display can get really confusing because you have to “imagine” the missing dimension.

The Geometry Editor can display the antenna four different ways; in three dimensions, the YZ plane, XZ plane, and the XY plane. The last three planes help us design an antenna two dimensions at a time. In the three dimension view, the X,Y, and Z axis all meet at the origin coordinates (0,0,0).

Click on the Geometry Editor button to display the X and Y axis. By convention, the X-axis would be the “boom” of the antenna. If no boom, as we’ll see creating a dipole, it’ll be drawn over the origin (0,0), with one-half of the antenna on the positive Y axis and the other half on the negative Y axis. For example, a three element beam looks like this:

3-Element Beam in XY Plane
3-Element Beam in XY Plane

The driven element (DE) is drawn on the Y-axis, with the reflector (REF) and director (D1) are drawn parallel to the Y-axis and spaced along the X-axis. Right now this antenna is laying on the ground! 4NEC2 will not like this; that’s where the Z-axis comes in.

The Z-axis is the height of the antenna above ground. Working this way allows you to concentrate on drawing the antenna in two dimensions, then by adding in the antenna height in the Z-axis, the antenna will move up in height. You won’t see this in the XY plane view because the Z-axis is coming out of the display right at you. Put your finger over the letter Z and that’s where the Z-axis is right now.

To raise the height of the antenna, click on a wire, then in the Wire data section, add the height to the Z-axis; the Z-axis is the highlighted text boxes.

Raising the Antenna
Raising the Antenna

Remember you have to add height to the Z-axis for both ends of the antenna and the values are always positive. Putting a negative value for the Z-axis will place the antenna underground!

Click on the Geometry Editor button, the antenna will no longer be on the ground.

Antenna Height
Antenna Height

Now that we’ve seen how to use the Geometry Editor, we’ll draw out the 20M dipole antenna.

Drawing the Dipole

To calculate the halfwave length of a dipole, use the standard equation:

$$ Length = \frac{468}{f_{r}} $$ $$ Length = \frac{468}{14.175} $$ $$ Length = 33.01 feet $$

We can call that 33 feet for this demonstration. When building this antenna, you’d want to make the overall length longer to account for the feedpoint and supporting the ends of the antenna. Plus, the ground underneath the antenna will also come into play so the length derived from the equation could be slightly shorter or longer.

Helpful Math Trick

Here’s a simple math trick to figure out if 468 isn’t correct for your area. When the dipole is installed at the length of the standard equation determine the SWR at resonance. For example, resonance happens to be 14.234 Mhz. Slightly higher than calculated. Here’s the math to figure out a new constant where:

Original Length: 33

New Resonant Freq: 14.234

$$ 33*14.234 \widetilde{=} 470 $$

Now the equation for a dipole at your location is:

$$ Length = \frac{470}{f_{r}} $$

Do the calculation one more time using the new constant to determine the new length and the new dipole will be resonant at the design frequency. Anyway, back to using 4NEC2!

To draw the antenna in the Geometry Editor, click on the Geometry Editor toolbar button, on the right, use the Zoom slider to make each grid square 1 foot long, then enter the design frequency in the Frequency textbox. When you’re done, the Geometry Editor should look like this:

Editor Configuration
Editor Configuration

Now that the Geometry Editor is configured, click on the Geometry Editor button then draw a line as evenly as possible along the Y-axis with half the wire on the negative Y-axis, and the other half on the positive Y-axis. Click OK on the Wire Radius dialog box.

Wire Radius
Wire Radius

There’s a few more configuration steps before analysis. This dipole will be made out of 14AWG wire and right now it’s 32 feet long. We need 33 feet so enter .5 in both Y-axis textboxes. The dipole is one long segment, that needs to be changed as well. Enter the following into their respective textboxes:

  • Segs: 11
  • Radius: #14
  • End-1 ft: 16.5
  • End-2 ft: -16.5

The geometry editor should look like this:

Antenna Details
Antenna Details

One more issue to address and that’s getting the antenna off the ground. We’ll analyze this antenna at \( \frac{\lambda}{2} \) above the ground which is 33 feet. Remember the Z-axis is for height above ground so enter 33 into both End-1 and End-2 text boxes.

Antenna Details
Antenna Details

The dipole is now 33 feet long with 11 segments and is 33 feet above ground.

Adding Ground Underneath the Dipole

4NEC2 has a wide range of ground types to choose from. Knowing which one for your area isn’t too difficult to figure out. By observation, the ground around the author’s location is slightly sandy and rocky mostly dry. Take a look around your location to see what the ground looks like. 4NEC2 has the following ground types available:

  • Free Space
  • Fast Ground
  • Perf Ground
  • Real Ground

To choose which ground to use, click on the on the toolbar and the Ground Parameters pane will appear. Select Real Ground from the drop-down, then from the lower drop-down, select Dry, Sandy, Coastal or your own ground type if you prefer. The settings look like this:

Ground Type
Ground Type

Adding the Source

All that’s left is adding the source of RF to the dipole. The source will be placed right in the center of the antenna, which would be segment 6. This is the reason why it’s best to choose an odd number of segments. By placing the RF source on segment 6, that leaves 5 segments on either side of the source. Some antennas don’t have their sources in the middle and that will be discussed in the chapters on antennas.

To add a source, click on the then buttons. Click the button, move the cursor on the grid and it will change to dark cross hairs. Hold down the left mouse button and drag the source to the center of the dipole coordinates (0,0). The Geometry Editor will look like this:

Source Added
Source Added

The source is the circle centered on the origin. Sources will always be placed in the middle of a segment.

The very light gray rectangle represents that there is a ground underneath the dipole. Click on the Geometry Editor button to see the final creation!

Source Added
Source Added

Analyzing the Results

Now it’s time to analyze this dipole. Click on the button on the far right side of the Geometry Editor; the Generate window will be displayed. Select Far Field.

Source Added
Source Added

Click on the Generate button!

What do the results look like? The Main Window gives us the electrical details of our dipole at a half wavelength above ground. We know the feedpoint impedance, S.W.R., radiation efficiency, etc.

Main Window
Main Window

The part we’re interested in is the vertical gain, where is the signal going when it leaves the antenna and heads towards the horizon. At \( \frac{\lambda}{2} \) above ground, it looks like this:

Vertical Gain 1/2 Wave Above Ground
Vertical Gain 1/2 Wave Above Ground

The main lobe is \( 30^\circ \) above the horizon over real, dry, sandy, coastal soil. What would the vertical gain look like at different heights? Change the Z-axis to 16 feet or about \( \frac{\lambda}{4} \) above the ground. After calculation:

Vertical Gain 1/4 Wave Above Ground
Vertical Gain 1/4 Wave Above Ground

That’s called a “cloud warmer” - the major lobe is at \( 70^\circ \) above the horizon. Great for local communications but not so much for chasing DX. In any case though, it’s better than no antenna at all!

Change the Z-axis to 48 feet or \( \frac{3}{4}\lambda \) wavelength above ground. What does that look like?

Vertical Gain 3/4 Wave Above Ground
Vertical Gain 3/4 Wave Above Ground

Now the pattern really changes! Our major lobes are now \( 20^\circ \) above the horizon. What has caused the signal to have a lobe going straight up? The ground beneath the dipole is acting like a reflector. The dipole is still emanating a signal a full \( 360^\circ \) but the distance to the ground is such that the signal that’s reflected back up adds to the signal that’s already going straight up. Gives it a clown hat like shape.

What does \( 1\lambda \) look like? Enter 66 in the Z-axis and generate another set of results. It looks like this:

Vertical Gain 1 Wavelength Above Ground
Vertical Gain 1 Wavelength Above Ground

The major lobe is now \( 15^\circ \) above the horizon, but the lobe pointing straight up has been squished down some and widened.

What does \( 2\lambda \) above ground look like? Enter 123 for the Z-axis and generate another set of results. It looks like this:

Vertical Gain 2 Wavelengths Above Ground
Vertical Gain 2 Wavelengths Above Ground

The major lobe is now \( 10^\circ. \) above the horizon, but more lobes have appeared and the straight up portion is narrower than before.


Modeling antennas isn’t all that difficult. This example we used a 20M antenna modeled at various heights above real ground. The pattern that shows for every \( \frac{\lambda}{4} \) the antenna is above ground, the major lobe angle drops by about \( 20^\circ \). It’s not until we reach \( 1\lambda \), where the major lobe is at its lowest - the best for DX communications. Going another wavelength higher, the major lobe angle starts to increase again, so going higher isn’t always better.

** The following chapters are in the full version of 4NEC2 The Definitive Guide **

Chapter Four - 4NEC2 Editors

4NEC2 Geometry Editor

NEC Editor (New)

NEC Editor

Notepad Editor

Chapter Five - Geometry Builder

Chapter Six - Optimizer

Chapter Seven - L/Pi/T Matching

Chapter Eight - Graphing with gnuplot

Chapter Nine - Using ItsHF & VOACAP


Area Coverage


Chapter Ten - Verticals

Very Short Verticals

Quarter Wave

40M and why it works on 15M.

Half Wave

5/8 Wave

Mobile Antennas

Chapter Eleven - Multi-Element


Log Periodics


Chapter Twelve - Loops

Single Band Loop

Multiband Loop

Magnetic Loop

Chapter Thirteen - VHF/UHF/SHF Antennas





2.4 GHz Pringles WiFi Antenna

2.4 GHz High Gain Loop WiFi Antenna

Chapter Fourteen - Antenna Menagerie!

In no particular order, it’s a menagerie after all!



80M Parabolic

A tribute antenna to KV7J(SK) and WD8OSU.

Appendix B - NEC User Manual Installation

Appendix C - Gnuplot Installation & Configuration

Appendix D - ItsHF & VOACAP Installation & Configuration

4NEC2 Function Keys & Keyboard Shortcuts Cheat Sheet

Main Window

Function Keys

F1 -> Opens the Main Help file.

F2 -> Opens the Main 4NEC2 program window.

F3 -> Opens the Geometry window.

F4 -> Opens the Pattern window

F5 -> Opens the Gain/SWR/Impedance window

F6 -> View or Edit 4NEC2 data window

F7 -> Generate/analyze antenna system

F8 -> View NEC output-file using default editor

F9 -> Start/select 3D-viewer window

F10 -> Calculate L/Pi/T Matching

F11 -> View interactive Smith Chart

F12 -> Opens Optimizer/Frequency Sweep window

Keyboard Shortcuts

W -> Exciter/Load Info Window

X -> Polar notation

CTRL + O -> Open 4NEC2 file.

CTRL + P -> Print current window.

CTRL + S -> Save 4NEC2 output file.

CTRL + Z or ESC -> Quit 4NEC2.

CTRL + F1 -> Use Notepad Edit

CTRL + F2 -> Use NEC editor

CTRL + F3 -> Use Geometry Edit(or)

CTRL + F4 -> Use NEC editor (new)

Geometry Window

Function Keys

SHIFT + F4 -> Export Structure

Keyboard Shortcuts

A -> Auto-segm. log

B -> Current + Phase

C -> Current magnitude

D -> Last NEC-input

E -> Open ends

F -> Fix rot-center

G -> Change orientation

I -> Input file

J -> Junctions (>2)

K -> Step-rad. log

N -> Wire Numbers

O -> Output file

P -> Phase only

Q -> Run geometry check

R -> Near/Far field

S -> Segments

T -> Tag Numbers

U -> Use traditional disp.

W -> Struc/Wire load

X -> Polar notation

Y -> Current real

Y -> Show geo-check

Z -> Current imaginary

1 -> Segm. L(ength)

2 -> Segm. R(adius)

3 -> Segm. Len / Rad

4 -> Junc. L big/L small

5 -> Junc. R big/R small

6 -> Len / Rad

7 -> Surface-patch Area

9 -> Run segment checks

0 -> Show all seg-checks

HOME -> Reset

PU -> Zoom In

PD -> Zoom Out

RIGHT -> Next frequency

LEFT -> Prev frequency

? -> Identify W/S (Wire/Segment)

ALT + UP -> Incr. Log-factor

ALT + UP -> Decr. Log-factor

ALT + RIGHT -> Next

ALT + LEFT -> Previous

ALT + HOME -> Set as Center

CTRL + P -> Print

CTRL + Q -> Changes colors

CTRL + Left -> Shift Left

CTRL + Left -> Shift Right

CTRL + Left -> Shift Up

CTRL + Left -> Shift Right

CTRL + Left -> Shift Down

SHIFT + P -> Phase as color

SHIFT + R -> Export Far-Field

SHIFT + Y -> SYmbol conversion

SHIFT + ? -> Identify Tag

Pattern Window

Keyboard Shortcuts

B -> Show Bold lines

D -> Show both hor/ver

G -> Structure

H -> Show MPE colors

I -> Info

J -> Indicator

L -> ARRL-style scale

M -> Show Multi pattern

O -> Smooth line plot

> -> Next pattern

< -> Previous pattern

PU -> Inc. struct-size

PD -> Dec. struct-size

RT -> Next Phi/Az slice

LT -> Prev Phi/Az slice

RT -> Next The/El slice

RT -> Prev The/El slice

HOME -> Select No Normalization

DEL -> Set max scale value

RT -> Next Z, Y or X pos.

LT -> Prev Z, Y or X pos.

UP -> Inc line plot Y/Z Pos.

DN -> Dec line plot Y/Z Pos.

PUP -> Change to line plot

PDN -> Change to 2D view

INS -> Add new pattern

DEL -> Remove pattern

ALT + HOME -> Incr. log-factor

ALT + HOME -> Decr. log-factor

CTRL + P -> Print

CTRL + Q -> Change colors

SPACE -> Show Vertical Plane

SPACE -> Each tap will display XY, XZ, or YZ Plane

Smith Chart

Keyboard Shortcuts

G -> Course grid

S -> SWR Circle

X -> Polar Notation

HOME -> Normalized

INS -> Insert Z/Y

DEL -> Delete Z/Y

RT -> Next frequency

LT -> Prev frequency

CTRL + P -> Print

SHIFT + LT -> Move to gen.

SHIFT + LT -> Move to load

Change Log

v2.0 08/14/2021 :: KA6WKE :: General updates to manuscript, tpyo hunting & fixin', move to github for publishing

v1.1 08/22/2015 :: K9SRV :: Fixed typo in equation for dipole in graphics and text.

v1.0 07/25/2015 :: KA6WKE :: Initial sample release.

Appendix A - Directories & File Locations

Default 4NEC2 installation directories and file locations. Not all files are listed, only the ones the end-user can modify including examples, output & plot files.

 1 C:\4nec2>
 2 │   Cards.rtf <- NEC2 reference card.
 3 │   Nec2.doc  <- NEC-2 Manual, Part III: User’s Guide.
 4  5 ├───data <- Support files to add custom parameters and specifications.
 6 │       Coax.txt     <- Coax cable parameters.
 7 │       Conduc.txt   <- Wire conductivity constants.
 8 │       default.pov  <- Customize the scene in which the NEC2 structure or far-field pattern i\
 9 s placed.
10 │       Dielec.txt   <- Add custom dielectric constants for different materials.
11 │       Edit2.txt    <- Deprecated
12 │       Edit4.txt    <- Deprecated
13 │       Freqs.txt    <- Frequency-list (in mhz) for freq-sweep 'from file'.
14 │       Ground.txt   <- Conductivity and dielectric constant for different ground types.
15 │       Sunspot.txt  <- Sunspot numbers through 2020.
16 │       Symbols.txt  <- Default SY(mbols)/constants to be used in 4NEC2; Pi, wire radius, etc.
17 │       ToolTip2.txt <- NEC2 help text for Nec edit (new) DO NOT CHANGE!
18 │       ToolTip4.txt <- NEC4 help text for Nec edit (new) TBD - DO NOT CHANGE!
19 │       _ReadMe.txt
20 21 ├───exe    <- Main binaries and other files used by 4NEC2.
22 23 ├───its    <- ITS HF recieve and transmit coverage sample files. See: http://www.greg-hand.com\
24 /hfwin32.html
25 26 ├───models <- Plenty of examples of HF/VHF/UHF antennas.
27 28 ├───out    <- Input file for NEC2 and output files generated after NEC2 executes.
29 30 ├───plot   <- Dirctory used to store various plot files when exporting to GAM formatted file &\
31  used by gnuplot.
32 33 └───pov    <- Persistence of Vision Raytracer. See: https://www.povray.org/


1See Directory and File Locations Appendix.

2Cards are documented in the Editors Chapter in the full version of this book.