Each pattern file type is compatible with various coverage simulation software packages available today. Click on the links below to download the corresponding ZIP file of your choice. For TIA/EIA-804-B standard files download our ADF library, compatible with many popular propagation simulation software packages available today.
MMANA Antenna Modeling Program Tutorial, Part 1 A step-by-step inverted-coat-hanger antenna MMANA modeling program design example M MANA is a powerful antenna modeling program that is fascinating to experiment with. It can model a wide range of antenna types, calculate radiation patterns, power gains, front-to-back ratios, feed impedances, bandwidths, the effects of loading inductors, capacitors and resistors, the effects of resonant traps, the effects of some types of transmission lines, and other things of interest to anyone interested in antennas. However, there are important issues that can totally invalidate results, there are some annoying software bugs to avoid, many program capabilities are not immediately obvious, and the documentation is limited. All that combines to leave many first-time-users wondering how to begin, and if they do begin, wondering whether the results they obtain are valid. If that is your situation, this step-by-step inverted-coat-hanger antenna design example won't teach you everything there is to know about MMANA, but it will get you started, and probably will get you hooked. Warning Be forewarned that it won't take you long to learn the basics so you can start modeling your own antennas, but it may be days, weeks or months, before you 'surface for air,' because it seems the results from every new antenna design raise more questions you won't be able to resist exploring.
How much wider will the bandwidth be with 12 AWG rather than 14 AWG wire? Will the feed impedance match the feedline better if the antenna is raised slightly higher? If the feed impedance changes, how will that affect the bandwidth? Will the resonant frequency change? In which direction and how much? What will the height increase do to the radiation pattern? What effect will it have on main-lobe gain.
What will happen to the side lobes? What will happen to the front-to-back ratio? How much wider would the bandwidth be with a folded dipole? Would folding the dipole change anything else? Would changing to a gamma match change the bandwidth? In which direction and how much? How would adding another driven element, another director, or another reflector change all these things?
What would be the effects of changing the dipole driven element to a two- or three-element log-periodic driver? Should parasitic element spacings be different with a log-periodic driver? Does optimum parasitic element spacing depend on height about ground? There is no end to the permutations and combinations you can try from the convenience and safety your computer screen without spending a dime, assuming your spouse doesn't file for divorce while you are otherwise engaged! If you decide to read on, despite this warning, remember you were warned.
Why Model an Inverted Coat Hanger Antenna? Any antenna could be selected as a tutorial example.
An inverted-coat-hanger antenna was selected because someone asked how to model the antenna and because it is an unusual antenna others may be interested in. MMANA Computer Requirements Operating System MMANA is a Win32 application program that will run under any modern version of Windows, but it will not run under any version of UNIX, Linux or Mac operating system. Disk Space MMANA program files require only 1.1 MB of disk space. Antenna description files you will create require additional space, but those files are very small, so the total disk space requirement is meager compared to the needs of most modern application programs. Memory In contrast, MMANA memory needs are rather large. MMANA will run with small a amount of available memory, but you will be limited modeling very simple antennas or to modeling slightly more complex antennas with results that will not be very accurate. The required amount of memory varies depending on the version of Windows MMANA is used with.
Your computer should have at least 256MB of physical memory installed if you are running MMANA under Windows XP. You will be able to model significantly more complex antennas with accurate results if your computer has 512MB of memory installed.
1GB of physical memory will be even better. The First Step ( If MMANA is already installed, jump to ) If you haven't done so already, so you will be able to duplicate the antenna design steps that follow. However, you should close any other programs that are running before doing that, because a large number of Dynamic Link Libraries (DLL's) are shared by Windows programs and installation programs cannot upgrade DLL's that may need to be upgraded if they are currently being used by another program.
A dialog box will appear when you click the MMANA program download link. The exact text you will see depends on the version of Windows you are using. With Windows XP the dialog box title-bar will contain the 'File Download - Security Warning' shown on the next page.
EZNEC 6 Demo running with WINE on Linux You can easily notice the list of parameters EZNEC allows to be configured and stored describing our project antenna. For this discussion we have selected the design frequency of 300MHz. You can select any frequency you wish, but this is our choice for this demonstration. Essentially, CAD program use is made to be cosmetically similar to manual design. Meaning that the same parameters used to design and model antennas by hand are used in EZNEC.
Each parameter is presented in the list displayed on the main window of EZNEC. The results of most will be presented in a separate window, such as the display of the wires in the window just to the right. You will notice that calculations have been made to also display the RF currents along the wires displayed as the curved colored line above the antenna. Also shown in this pictorial is the window for wire edit and the calculated far–field pattern generated by the antenna currents.
All of the windows shown in this pictorial depend entirely on the selections made and the successful calculations of EZNEC. Because of the complexity of antenna design and the numerous features of the EZNEC program, we will not go into all of the options and methods here. If you are interested in EZNEC and it’s use you can find a printable manual at MMANA-Gal. MMANA-Gal Basic running with WINE on Linux Another Windows–based CAD program has almost as long a history as EZNEC. The application is known as MMANA-Gal.a conflation of the original name MMANA, and the maintainers’ initials. The original MMANA was designed and released as freeware by Macoto Mori, JE3HHT.
Mori San maintained the application for years before releasing the code to Alex Shewelew, DL1PBD and Igor Gontcharelko, DL2KQ. It is now known as MMANA-Gal Basic as freeware, and MMANA-Gal Pro as a commercial product. MMANA-Gal attempts to make the user interface simple and easy to use with the employment of integrated tabs instead of separate windows as in EZNEC. It employs extensive use of the 'method of moments' calculation technique.
Method of moments element method The method of moments (MoM) or boundary element method (BEM) is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations (i.e. In boundary integral form). It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, fracture mechanics, and plasticity. MoM has become more popular since the 1980s. Because it requires calculating only boundary values, rather than values throughout the space, it is significantly more efficient in terms of computational resources for problems with a small surface/volume ratio. Conceptually, it works by constructing a “mesh” over the modeled surface. However, for many problems, BEM are significantly computationally less efficient than volume-discretization methods (finite element method, finite difference method, finite volume method).
Boundary element formulations typically give rise to fully populated matrices. This means that the storage requirements and computational time will tend to grow according to the square of the problem size. By contrast, finite element matrices are typically banded (elements are only locally connected) and the storage requirements for the system matrices typically grow linearly with the problem size. Compression techniques (e.g. Multipole expansions or adaptive cross approximation/hierarchical matrices) can be used to ameliorate these problems, though at the cost of added complexity and with a success-rate that depends heavily on the nature and geometry of the problem. BEM is applicable to problems for which Green’s functions can be calculated.
These usually involve fields in linear homogeneous media. This places considerable restrictions on the range and generality of problems suitable for boundary elements. Nonlinearities can be included in the formulation, although they generally introduce volume integrals which require the volume to be discretized before solution, removing an oft-cited advantage of BEM.The method of moments was introduced by Pafnuty Chebyshev in 1887. – Wikipedia We include this rather technical explanation to indicate that all antenna assisted design software is an approximation based on calculation of minute portions of the total antenna.
The antenna elements are divided into segments, and the NEC engine calculates against each segment (often based on the previous or connected segment). 4nec2 For Windows. 4nec2 running with WINE on Linux This application is more about the technical aspects of antenna design than user friendliness. It allows the use of several numerical calculation engines such as NEC2d, NEC2d extended, and NEC4d. You can even design and use your own calculation engine following the application programmer interface (API) outlined in the developer documentation. As shown, 4nec2 displays the wire edit, and calculation output in separate windows.
Despite this relative user unfriendliness, this is a more than capable application for the antenna designer. Like the EZNEC application, 4nec2 (as the name implies) uses the NEC engines for calculation. The numeric electromagnetic coding (NEC) engine is a popular antenna modeling system for wire, geometric, and surface antennas. It was originally written in FORTRAN in the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory. The code was made publicly available for general use and has subsequently been distributed for many computer platforms from mainframes to PCs. 4nec2 is several times faster than EZNEC on simple designs, and frequency sweeps on designs such as our example. The antenna description is a more familiar NEC file.
A legacy format from the Fortran days of early NEC software mentioned above. However, it should be recalled that each of the highlighted applications uses a different method to calculate the output.
EZNEC uses the NEC 2 and NEC 3 methods. The 4nec2 application can use the NEC2d, NEC2d Extended, and NEC4d methods. For this, and several other reasons, there will be differences in the results between EZNEC, MMANA-Gal Basic, and 4nec2. It is recommended you do your own experimentation against the real world and see which fits your model better. Sadly, many new users opt for appearance and convenience rather than proven accuracy and repeatability.
Constructing The Model So, we have an idea for an antenna and we wish to model it on the computer. From this point on in our discussion, we will arbitrarily use the MMANA-Gal application to construct our model. It easily, and best illustrates, all the points we will be making in this discussion. Of course, the same model could be made in any of the programs shown here with slightly varying results. Making the wire model When modeling an antenna design, all modeling programs use a description file that tells the application what to calculate against. They may differ in the input methods, but all require the antenna to be described as a series of wires (even if it is constructed of pipe) connected together in a fix way.
The model is just that — a model. Author AD5XJ In our illustration, MMANA-Gal does this with a table of figures on the Geometry Tab (see the pictorial above.). The entry of figures in this tab should be familiar to anyone who has used a spreadsheet application. Each column represents different aspects of the antenna element(s). In our model, we have one element with two sections. So, there is only one line in the table that describes the antenna elements. All elements of an antenna model are described by X,Y, and Z coordinates.
The X and Y coordinates are in the horizontal plane, and the Z coordinate is the vertical plane. So how do we know if our model has reached that goal? Observe the next illustration. This graph is of the calculation results of our input to the MMANA-Gal Basic wire description. We obtained the plot by clicking the Start button to get a calculation then the Plot button on the Calculation page. The graph has three legends, on the left the “real” part of the impedance, and on the right the “imaginary” values.
At the bottom you will see a range of frequencies used to plot this graph. You will notice the red “imaginary” value line crosses zero very near our design frequency of 300 MHz while the “real” value crosses that frequency at the same time with a value of about 72.2 ohms. This is a very graphic illustration of one of the principals laid out in earlier lessons.
Without changing anything but the frequency, the feedpoint impedance makes a dramatic change. If this is confusing to you, review the lessons again until it becomes more clear. Now we know that our model is resonate (the +jX value is zero at the design frequency) and the “real” part of the impedance is 72.2 ohms. We can match that with 75 ohm coax easily. What is the SWR since we know a impedance mismatch is one source of SWR? The SWR tab of the Plots window will display the estimated SWR for the same range of frequencies as before.
This is more like what we are after. Within the narrow range of frequencies used for calculation, we have a SWR range of well below the 1.10:1 values. And at our design frequency, we have a 1.04:1 SWR. Any loss of signal using 75 ohm coax in this design will be negligible at this frequency (given the use of good quality coax like RG-214 or RG-6x). Notice that the frequency span is 4 MHz.
Very broadband for this frequency given our choice of dimensions (i.e. Use of 1/4 pipe instead of wire). Could we use a balun to connect RG-8/U or LMR-400 to our antenna? Sure, but the mismatch would be much greater and the resulting SWR would be also.
Not a desirable situation. Most baluns are constructed as 4:1 (200 ohms: 50 ohms) or 1:1 (50 ohms: 50 ohms) transformers. Doesn’t help much. We would need a 1.5:1 balun.
The use of a coaxial match is likely since the ¼λ is inches instead of feet. A short length of higher impedance coax in line with our 50 ohm coax will transform the impedance for us. The use of a traditional wire transformer balun is possible. They are available, but hard to find. There are homebrew instructions on the Internet if you want to make one for yourself (which is highly advisable for this model).
Courtesy ARRL Antenna Book 20th Edition pp.18-5 A simpler, and more flexible, and effective solution, may be to use what is known as a stub match. A stub match is designed with a wire that forms a ½λ “U” shaped connection between the two halves of the antenna. Our 50 ohm coax is connected at the spot where the match stub presents a 50 ohm load.
If you recall, in our previous lessons we presented the case of the “J–pole” antenna. It is unique in its use of the ¼λ stub as the bottom portion of the antenna. The coax is connected at the 50 ohm load point. Our diplole presents the same matching problem easily solved with such a device. However, instead of the stub having one side open as with the “J–pole”, we connect the other side of the stub to the second portion of our dipole as shown.
The last aspect of antenna design we want to look at is the pattern of radiation our antenna is expected to have. To see what has been calculated, click on the Far–Field tab to see what to expect from our design. Shown here is the calculated far–field radiation values in the horizontal (azmuth) plane and in the vertical (elevation) plane. This short tour is only the surface of what is capable with the software mentioned.
If you are interested in further study using CAD software, we recommend: Computerized Antenna Modeling Continuing Education Online Course and accompanying student handbook American Radio Relay League Publications Newington, CT One word of caution to those of you who try to model antennas. The model is only as good as the data given it. It is possible to provide what looks good, but yield misleading results. Consult your Elmer before attempting to construct a physical device. Experienced Elmers know the difference and can help correct any apparent errors before you spend your hard earned dollars on construction.
You may find yourself doing repeated caculations and adjustments to various parameters of the antenna description to reach your goal. It is a procedure that taxes the patience and perseverance of the model maker. The model is just that. It is a model. You can construct a precise physical duplicate of the model and when it is placed in a real world environment, it will display different values on an analyzer than calculated. That is because we can only estimate what it will be. Hopefully, the modeling software you used will be dependably accurate and not have significant differences.
All computer modeling has that same flaw. Never expect perfect results. The CAD program will get you very close, but there is no substitute for actuality. This model has been using MMANA-Gal Basic for our illustration. Does that mean that EZPAL is significantly different?
In fact EZPAL will need exactly the same parameters to describe the antenna as MMANA-Gal. The same is true for 4nec2. What is different is how the user interface provides for this input and the ultimate results offered by the model. For specifics on each CAD application, refer to the user documentation on the particular CAD program you wish to use. Have fun designing and building your antenna.