MMANA Antenna Modeling Program Tutorial, Part 1

MMANA 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 Tutorial Part 4)
If you haven't done so already, download and install the MMANA program 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.

• MMANA Antenna Modeling Program Tutorial, Part 2