mong scientists, engineers, and serious antenna experimenters, the term balun tends to have a specific meaning. Among those who are new to antennas, the term has so many meanings that it may mean nothing at all. It has become—for better or worse—a catchall term, and what serves as a catchall also serves as a wastebasket.

Balun, so far as I have read, is a functional description of some unspecified device or combination of devices. It transforms a balanced load to an unbalanced source. It has a counterpart term, the unun, a device for transforming an unbalanced load to an unbalanced source. We do not encounter the unun unless we are looking for another function often performed by either device. However, we shall initially focus on the balun.

What eludes many new antenna users and experimenters is why we should wish simply to convert a balanced load to an unbalanced source. Perhaps the most usual reason is to prevent common-mode currents from appearing on the surface of unbalanced feedlines, such as the ubiquitous coaxial cable used in most amateur, government, and commercial services to transfer energy between the transmitting and receiving equipment and the antenna. The use of a balun can largely confine the currents at the antenna’s feedpoint to the coaxial cable’s inner conductor and the inner surface of the outer conductor. In this way, we avoid unwanted radiation from the coaxial cable feedline and also avoid having to deal with unwanted RF currents at the station, where they may disrupt sensitive equipment, bleed into auxiliary functions, such as telephone lines, and shock fingertips in sharp points in the equipment cabinetry.

We can perform many of these functions with numerous devices. Perhaps the most common forms of baluns are the transmission-line transformer, the wide-band standard transformer, the coaxial-cable choke, and the ferrite-bead choke. The transmission-line transformer appears in various guises, using either air or ferrite cores and having either solenoid or toroidal forms. The most common toroidal transmission-line-transformer baluns appear in Ruthroff and Guanella designs, and perhaps Sevick’s writings have given this form of balun predominance if most antenna writings. However, many transmission-line transformers are lossy in the presence of excessive reactance in the load, and Sevick cautions that the antenna builder should compensate for the reactance between the antenna and the balun.

The wide-band transformer, normally wound on powdered iron cores for HF applications, has regained considerable popularity for certain applications. Such transformers require attention to using cores large enough to prevent saturation and to the distribution of turns on the core. Some manufacturers of terminated wide-band antennas prefer the wide-band transformer over the transmission-line transformer. Even though losses in the standard transformer are slightly higher than in a well-designed transmission-line transformer, they are insignificant compared to losses of the antenna itself due to the use of one or more terminating resistors.

Both coaxial cable and ferrite bead chokes function by using inductive reactance to choke off common-mode currents. In both cases, the key to effective use is obtaining sufficient inductive reactance to impede the flow of current on the outer surface of coaxial cable braid. Ferrite bead chokes require attention to ferrite bead heating under high-power applications. Both type of choke are useful not only at the antenna feedpoint, but also at the entry to the equipment station. In the latter position, they can also choke common-mode currents that may couple onto the cable’s outer surface from a variety of sources. Since they are in-line devices, they serve equally well as balun and as ununs. However, both types of chokes are subject to losses where the impedance has a considerable reactive component.

So far, we have not mentioned the transformation of the antenna’s feedpoint impedance (or the impedance on the transmission line at any other point of installation) to some other value. Unfortunately, the term balun has erroneously come also to mean to the new antenna user a device for changing impedance. However, this function is separable from the balanced to unbalanced function of some devices. Of course, chokes do not transform impedances when used within their proper limits. That leaves us with the transformer types of baluns.

If we approach the subject of impedance transformation, then the balun transformer is only one of numerous ways to achieve the goal. We may use both balanced and unbalanced networks of reactive components to transform one impedance value to another. We may use also transmission lines—either singly or in combination—to effect an impedance transformation. Both methods are equally effective in principle. Newer antenna users rarely realize that the beta match at an antenna’s feedpoint (a form of L-network) is identical in principle to the design of some antenna tuners. They also do not realize that the quarter-wavelength matching section is closely related to the transmission-line transformer, but has a much narrower useful bandwidth.

Wide-band transformers of either the transmission-line or the standard types generally have a single impedance transformation ratio—and at most a small collection of ratio steps. In contrast, networks may use fixed or variable reactive components to handle a wide variety of ratios—and to compensate for reactive components in the impedance at their load terminals. There are a few applications for transmission-line and standard transformers where the single step may serve over a seemingly broad frequency and impedance range. For example, a 4:1 ratio in a transformer will handle load impedance excursions from 100 to 400 Ohms and still return a 50-Ohm SWR of 2:1 or less. When newer antenna users look into their single-ended network antenna tuners and see a 4:1 balun for use with balanced feedlines, they have no idea if the design is lossy from careless design or construction, and they make another mistake as well. They also assume that the impedance at the terminals of the balun’s load side is high and needs downward transformation to allow the tuner to operate efficiently. In reality, for a multi-band wire antenna—the most common application calling for a balanced transmission line and a tuner—the odds are quite high that the terminal impedance will be low, sometimes very low. Transformed, it will be even lower. Such loads often show an ease of obtaining a 50-Ω match with less than a 2:1 SWR, but often at the cost of considerable energy loss. Some of the most recent single-ended tuner designs have allowed the circuitry to float (to avoid giving common-mode currents a by-pass to other equipment) and have placed a 1:1 choke or balun on the input side, where it is always within reactance limits for the device.

None of these points require repetition to the experienced antenna experimenter, who knows from that very experience what assumptions to make when another writer mention inserting a balun of a certain sort into a feedline system. However, we need to use care with respect to less-experienced readers. We need to spend an extra sentence or two to make clear to antenna novitiates what function(s) the device is performing in a given application—and, if apt, what other devices might do as well for that application. Moreover, we should not simply say that we installed a balun, but also say what type of balun we used. If we require an impedance transformation of a transformer-type balun, we should note that fact so that the newer reader can separate the balanced-to-unbalanced function from the impedance transformation function.

Unless a balun’s design is especially important to the focus of an article, the writer does not need to go into the technical detail of how the device achieves its goals. (On the other hand, antenneX welcomes articles on just these subjects, since the types of devices mentioned in these notes are important components within antenna systems.) Being specific about functions performed by these devices is essential even apart from such detail.

The more that we take the time to explain such matters in antenna articles, the more rapid will be the education of new antenna experimenters. Education is often a matter of clarity, and the more clearly and precisely we can use terms like balun, the more effectively we shall educate newer readers of antenneX. To repeat our quote of the month: I am glad to learn, in order that I may teach. —Seneca (4? B.C.-A.D. 65)

I am pleased to announce that antenneX has become an authorized distributor of the popular GeoClock Pro Software. The company's latest version 8.4 for Windows, with the Ham Package, is now available in the software section of the Shopping Shack. Along with the launch of the Grayzone (utilities) CD-ROM in December 2006 and ACE-HF Pro last month (February 2007), this product further expands the fine propagation tools we can now offer to the worldwide market. GeoClock Pro with the Ham Package is now available on CD-ROM or download.

• GeoClock is a 16-bit program and works with most versions of Windows from Win3.1x through WinXP and the new VISTA.

• The Windows version also includes Screen Saver and Wallpaper modes. However, be aware with the various changes to these Win-OSes from Win3.1x to Vista, using these may be problematic.

• GeoClock Pro shows the current time (based on your computer's clock) with a high quality map of the earth. The current sun position is displayed, and the parts of the earth in sunlight and twilight are highlighted. This display is automatically updated every few seconds. Local sunrise, sunset, the sun's azimuth and elevation, and times around the world are also displayed. A variety of map backgrounds and other options are available.

• With a registered copy of GeoClock Pro, you get the latest versions of the programs, 45 maps, zoom, distance measuring, local time displayed next to the city names, and immediate map display.

• GeoClock Pro can be used to watch the day-night terminator as it approaches your station. This is particularly useful during contests, when the higher-frequency bands often open at the onset of the daylight hours.

• GeoClock Pro includes the HAM PACKAGE Plug-in to provide special functions for HAM radio operators. It provides graphical display of remote station location, propagation path, and D and F layer illumination, together with key location, pointing, distance, and time data. The Ham Package includes a custom Azimuthal-Equidistant map centered on your HAM station, a call sign data base, and utility programs.

The HAM PACKAGE functions include:
• Azimuthal-Equidistant (Great Circle) map centered on your station
• Twilight and terminator, or D and F layer illumination, display
• User Maintainable call sign data base
• Remote station location
• Short and long great circle path
• Short and long path azimuth and range
• Remote station (reciprocal) azimuth
• UTC, local, and remote station local time
• DXCC and WAE designations
• CQ and ITU zones
• Continent, area, and location names
• Optional use of QRZ CD-ROM for US call signs.

• With ACE-HF installed on your PC, GeoClock can be used together with ACE-HF (System Simulation & Visualization Software) so you can watch the Open Bands Boxes and the circuit prediction charts while keeping an eye on the GeoClock terminator display. One handy screen arrangement is to call GeoClock from the ACE-HF Circuit Analysis screen, and then use the GeoClock Window Controls to reduce its window size. Put GeoClock in the upper-left corner of the screen.

• If you call the ACE-HF SNR Summary Chart, you can watch the summary predictions -- and even the ID timer if you have started it -- as well as the Main Chart predictions while you note the terminator's passage in the GeoClock window.

• ACE-HF (Animated Communications Effectiveness, High Frequency) is a new product based on the proven VOACAP program with a new interface and display routines based on GeoClock.

How time flies! With this month's popular propagation column, author Marcel De Canck,ON5AU of Belgium celebrates his 5th year as a monthly contributor to antenneX. But, not only has Marcel contributed the monthly columns, he has been very busy publishing a 3-volume set of books containing a collection of many of his works, including his unique animation wizards and workbooks which provide wonderful learning aids for a somewhat complex subject — in fact, many may say learning about propagation is now fun, thanks to Marcel.

But, his activities haven't stopped with columns and books. As mentioned above, Marcel developed a CD-ROM packed with useful propagation tools — the Grayzone CD-ROM identified above and announced in my December 2006 column of Stone's Throw!

May we all wish Marcel many more decades of such valuable contributions to radio activities enjoyed by many thousands around the world. Keep up the good work, Marcel!

Don't miss his new column in this month's issue! And, you can check out his books here.

NEW CONTRIBUTOR THIS MONTH
You will note the article this month by Eli Kovo, 4X4LH of Jerusalem, Israel entitled "The 4X4 Slimtenna." We are pleased to welcome him to our roster of writers from 25+ countries. By way of introduction, we present his brief biography:

THE PURPOSE OF THIS JOURNAL
In my column for September 2006, “The antenneX Mission,” I wrote about a subject close to my heart — the purpose of this journal. It had been quite some time since I had reminded our readers of our original purpose when we set out some 20 years ago.

More than anything else, this journal has always been a “labor of love” for me. It is the reason I founded the antenneX magazine almost 20 years ago, knowing that running a magazine is a tough business and especially so since I planned to do it without the traditional revenue support from advertisers or outside investors. I wanted this magazine to always be able to write about any issue without concerns of losing the support from any of those type revenues. I am pleased to say, we have never steered from that course one iota. And, as a consequence, we have covered some very controversial developments throughout the past two decades. In the process, we have provided valuable factual information to more than 200 countries, even to the most remote regions of the globe. Hence, our readers are much more informed about the truth about all of the “new” devices as their stories unfolded in the antenna and antenna-related field. For more details, you are encouraged to read my column from September 2006.

Additionally, we were pleased to receive and publish in the October 2006 issue, a very special editorial reaction to my column written by one of our long-term readers and contributors, Dr. Jef Verborgt. Those two articles are located by the following links below:

VISIT THE GUEST ROOMS
The relentless attacks on our web site by pirates and the like has made it necessary to add more security to protect our material against such piracy. It's only fair that we know who enters the House of antenneX, so our guests will need to provide some minimal information in the process of obtaining a login. This includes using your real active email address without which a login cannot be received. Do not confuse this login with a paid subscription login. They are not the same and your subscriber login will NOT work in the Guest Room areas. Of course, you may choose to create your own login to the Guest Rooms using the same login as your subscription, if the system will accept it.

Along with the continuing fight against spam/virii junk, protecting our material and valuable bandwidth against piracy takes up a great amount of our time—time we can't really spare. The Internet is simply not the friendly neighborhood it used to be in the "old days" and more and more security must be installed to counteract these intruders. Thus, we have made the access to the Guest Rooms as automatic as possible for you to manage your own login.

In view of the above, we have overhauled the numerous free and open-access sections that have always been wide open to all of our friends throughout the many years antenneX has been online. But, we must change with the times as the need dictates. I don't think the Internet will become more friendly in the near future and protected sites with logins are fast becoming the rule rather than the exception. To repeat, most would like to know who they invite into their house. The same applies at the House of antenneX. It's really worth the effort!

We have activated a new login system for access to the above guest rooms — and, the login can be totally managed by our guests. Above is a graphic of what you see as a login page to the new consolidated area, "antenneX Guest Rooms." This new page for logins is at this location now and available for your use:

As a result of this new programming, you will be able to obtain your own login, change it to update your info, change your password and delete membership if & when you desire without our help. Of course, the bottom link on the new page provides help if you still need it.

AN INVITATION TO CONTRIBUTORS
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antenneX thrives on the contributions of antenna experimenters, ranging from the informal home shop construction project to the theoretical investigation of basic antenna, feedline, and propagation phenomena. Over the years, we have published articles on the use of new or newly adapted materials, known antennas adapted to new circumstances, modifications of antenna structures, basic explorations of both common and unusual antennas, antenna modeling exercises, design improvements, antenna matching techniques from both a physical and mathematical perspective, evaluations of mini-antennas and their underlying theory of operation, new and patentable designs, propagation tutorials, and.... The list goes on, since no antenna-related topic is irrelevant to the readers of antenneX.

At the same time, antenneX has experienced continuous growth in its readership—for which we are appreciative. However, all readers can help us do even better. How? By submitting an article every now and then based on your current antenna work that may be useful at any level to other readers.

Among the engineering and researching readers, there are undoubtedly a number of unclassified and non-proprietary findings that antenneX readers would like to know. Among the practical antenna designers, there are ideas, tests, and numerous other practical findings to benefit our readers. Antenna builders very likely have some techniques to share with other readers. Besides the regular articles, we always have the home work shop column for shorter practical ideas and we always have the invited news and editorial column for information about new technologies, future advances, lost old but good ideas, and personal views on the good to bad things that are happening in the world of antennas and propagation.

If you are uncertain about whether your ideas merit an article, please feel free to send an outline to the general editor/publishers at manuscripts at antennex.com . Do not feel that you must be ready to be a regular submitter to write for antenneX, because we welcome the individual contribution as much as monthly articles. As well, do not believe that the slots in each issue are already spoken for—we shall always make room for a worthy article.

A 3-Band, 2-Element Spider-Supported Quad Beam
By L. B. Cebik, W4RNL

One of the most difficult tasks in designing a multi-band 2-element quad beam is obtaining full band coverage. This problem has two dimensions. One dimension involves obtaining at the antenna an SWR that is less than 2:1 relative to the impedance of the main feedline all across each of the bands covered by the beam. The second dimension covers other important operating parameters, such as adequate gain and front-to-back ratio across each band.

Impedance Matching of Transmission Lines
By Kirk T. McDonald, PhD
Joseph Henry Laboratories, Princeton University

This article considers several ways of "matching" two transmission lines such that a wave propagates from the first to the second line without reflection at the junction. As such, a transmission line is a device consisting of two parallel conductors such that TEM (transverse electromagnetic) waves can be propagated. Examples of transmission lines include coaxial cables, and simple 2-wire (Lecher) lines.

Baluns and Antenna System
Network Impedance Matching, Part I
By Fred M. Griffee, N4FG (EE Retired)

Previously, I reviewed my approaches using balanced and unbalanced impedance matching networks. In this article I address the efficiency of these various approaches. I also discuss failures that misled me (and probably others) into believing an SWR close or equal to a ratio of 1:1 for an input system having a surge impedance of 50 Ohms does not include discrepancies or associated failures. This experience will be shown to actually be dissipating 90 or more percent of the power in the matching network and balun or elsewhere rather than the antenna itself.

My findings will also relate to the balun winding that appears to be very sensitive to the termination it experiences, especially when the termination is a complex vector quantity. But most important is the need for a balun isolation impedance that is high enough to inhibit common mode current problems that may exist.

Resonant Wire Antenna Efficiency
By David Jefferies, PhD

This concise paper attempts to summarize the most important results (for radio amateurs) of my recent investigations of resistive loss in wire antenna structures brought about by the confinement of the RF current flow to a thin region near the surface of the metal of the wires, and consequent dissipation of supplied power in the thin layer of metal that actually carries the current.

Improved Antenna Performance for VHF FM
Some Basics, Some Options, Some Hurdles
By L. B. Cebik, W4RNL

FM operations in the amateur VHF region principally use vertical polarization. The ever-enlarging FM repeater and related simplex operation in the upper 3 MHz of 6 meters and 2 meters has expanded operator goals. Once, amateurs were content to work only local stations and repeaters. However, time has increased the desired repeater range, but with due regard to not causing interference to repeaters operating on the same frequency pair or an adjacent pair. The solution has been less a matter of increased power--since that one factor does not help reception. Instead, the solution has been the use of better antennas. Rubber duckies and other simple antennas will always have a place on handheld units, but home stations require something better.

Let's look at a few options for better antenna systems for FM operations, beginning with some basic antennas and their limitations. Next, let's turn to ways in which we can increase gain and directivity to obtain full coverage of the horizon. Along the way, we shall examine some of the practical hurdles that we must overcome to achieve the goal.

The 4X4 Slimtenna
By Eli Kovo, 4X4LH

Some of us prefer to spend a lot of money on towers, enormous in height and price, with multi-element antennas, and on top of that, we use the highest legal power. The rest of us, who must deduct hard earned money from the family budget, have to delve into the intricacies of efficient transmitting, propagation problems, and many other ingredients, if we want to still enjoy our hobby. It seems that today’s high-tech has brought the hobby to a discouraging state: we don’t build receivers and transmitters any more and on the operating side of it, we endlessly chase DX for a report and a QSL, which doesn’t seem to be the highest goal of our hobby.

Instead, if we get aware of the pitfalls we will benefit by better understanding of the how’s and why’s of antennas and enhance our station performance. This will hopefully encourage us to build and use simple, cheap and efficient, low take-off angle monoband verticals.

Well, there you have it, folks—thanks for listening and remember, the reading lamp is always on for you in the reading rooms. If I can be of further help, I'm just a Stone's Throw! away.-30-

Best reGARDS, Jack L. Stone, Publisher
jack@antennex.com
March 2007 antenneX Online Issue #119

	ACE-HF PRO System Simulation & Visualization Software
	GeoClock Pro with Ham Package The Sunlight Clock
	The Grayline Program - Unique Set of Utilities for Propagation