Look Ma – No Wires!

When you don't know anything, everything seems possible—Jack L. Stone (I think)

INTRODUCTION
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lmost a century ago, the term "wireless" encompassed all communications via radiated RF energy. Of course, it was short for wireless telegraphy. Long after the English-speaking world turned to the shorter term "radio," the French continued to refer to receivers as "la T.S.F." for "la télégraphie (ou téléphonie) sans fil." Only after World War II did "la radio" become the general term to abbreviate radio-telegraphy and radio-telephony.

In the 21^st century, "wireless" has taken on a new meaning. Some older radio people think that the new way of using the term is a corruption, but the term has stuck. Many electronic functions that once required wired connections now use RF links to free them of the wires. Between telephone and computer applications, the world has grown increasingly wireless. Simple and older applications were inadequate to establish the term. For example, garage-door openers made the move from wired buttons at the door to remote RF links in the 1940s. It took some special circumstances to set the stage for a wireless industry. Data links between mainframe computers gradually worked their way into personal computers linked to the worldwide web. Today, we almost cannot distinguish a cell phone from a full computer. The special circumstance relates to the need for broad bandwidth to handle the flow of digital data: wireless links moved into the frequency spectrum around and above 1 GHz.

The new realm—once inhabited only by a few inveterate experimenters—is now common territory for engineers and consumers. Extensive design work goes for new and better antennas to serve this portion of the RF spectrum through a variety of applications. Many of the antennas are very small. Giant microwave dishes and horns have given way to smaller, less conspicuous antennas that serve either to effect communications (between persons or machines) or to provide the first link in that process. In the wireless realm of today, wire and tubing have given way to copper strips either on or within a protective and supporting substrate. An entire full-size antenna might be smaller than the common N or UHF connectors used in the HF realm. And the antenna will be free of most of the wind, weather, and atmospheric attacks that shorten the life of an HF antenna.

TECHNIQUE CATCH-UP
Most of us are used to working with macroscopic materials and components. We are better tooled for wire and tubing than for copper-clad boards that contain circuitry, transmission lines, and antennas all rolled into one assembly. As well, our design and analysis software—the affordable packages—are mostly restricted to round wire elements. Finally, our test equipment rarely goes beyond the HF range, with only a few accessible pieces reaching into the VHF range. The 21^st-century version of wireless requires tools, techniques, and test instruments that are largely beyond the reach of the traditional basement or garage experimenter.

I wonder if this situation is necessary or whether it might be a simple absence of information? I recognize that most of the design software for this new wireless realm is proprietary and therefore very expensive. Most of it is far from user friendly. So even if we had ready access to the software, we might not use it as much as we do the simpler NEC and MININEC software that have become commonplace in the computers of antenna experimenters. Still, it would be nice to have access to the software just to see what we might come up with.

I also recognize that test equipment for the new wireless spectrum is very expensive. But I also have to wonder whether there are folks who can develop and disseminate information enough to develop versions of the equipment that are suitable for basic experimentation. If we can reduce the cost of such equipment from the present $10K to $20K range down to a few hundred dollars, we might find more home shops equipment well enough to effectively experiment with GHz-range antennas. Some instruments available to radio amateurs already go up to a half-GHz, but they have limited capabilities in that range. A new generation of basic instruments is necessary. As well, we need information on how to obtain clean usable instruments from the immediately preceding generation of test gear, the ones that labs in universities and in industry are replacing with the latest gear.

LEARN BY DOING
We also need more information on how best to work effectively with today's materials. What tools do we need and how can we best use them. It is one thing to design an antenna, but to test it we must first build it. Even if we had the design software and the test instruments at hand, we cannot prove out a design until we can construct a reasonable prototype that others might replicate and test for themselves.

The new wireless world of antennas is not a replacement for some of the on-going investigations that appear in antenneX. The research into small antennas for long wavelengths will always have an important place. However, the newer world of very small antennas for very short wavelengths is acquiring equal importance among antenna designers. Numerous industry journals are devoted to the region—although not devoted specifically to antennas alone. Of long standing are some "microwave" journals, and more recently, we find a journal devoted to "high-frequency" (meaning ultra-high-frequency) electronics. But little of the useful information in these journals works its way down to the home experimenter.

Of course, not all antennas in the UHF realm are full size. For example, RFID applications need small and efficient antennas that fit into chips affixed to various kinds of packages (or even inside pets and, someday, even people). The search for small antennas will always have a place in RF communications, whatever the frequency range of interest.

ARE WE REALLY READY?
So I wonder—without really knowing—if we are ready for the new wireless world. Are the information resources available to let the antenna experimenters who have sufficient interest enter into the realm of innovative GHz antenna design? If the information is available, what can we at antenneX do to help spread the right words to make the realm accessible to more of us?

BALUNS, NOT BALLOONS!
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During the past month of July 2005, one of the longest threads ever was launched on the antenna-discussion list about various types and use of baluns. From the length of these discussions and the many members that joined in on the debates in the threads, it leads one to believe there is much to learn yet about the methods and use of these components. Perhaps only our discussions about the behavior of photons on antennas come close to the variety of differing opinions exhibited here about many aspects of these devices.

In broad terms, baluns (balanced to unbalanced transformers and ununs—unbalanced to unbalanced transformers) are used as matching devices commonly known as transmission line transformers. Their primary purpose is to transmit the energy from input to output by some sort of transmission line mode (common or uncommon mode?). Thus, a balun (or unun) is simply a choke that isolates the input from the output and only allows transmission currents to flow—but, watch out—how does it flow?

THE JULY 4^TH FIREWORKS
The major debate about this subject was launched on July 4^th 2005 and then the fireworks were lit. Chris Trask made reference that he had written an extensive tutorial on the subject of the theory, design, and applications of transmission line transformers, or “TLT.” To that discussion Chris added more balun references: The “TEM” and the “Isolated TLT.”

Throughout the July discussions inspired by the content of those tutorials, Chris felt he should modify his original papers. Chris has provided the new revised documents that may be viewed now in the Guest Room Science Library at these URLs:

You will need a guest login. If you don’t already have a login, you may create one at: To Guest Rooms

Perhaps one reason for so much lack of specific knowledge about the balun/unun devices is that (as I have heard) our various Universities are not teaching us about them. Since this magazine reaches many of those Universities—Schools of Physics and Engineering, perhaps steps may be taken to correct that omission? Clearly the devices are an important component of antenna science, but largely misunderstood. Thus, the need for tutorials like those provided by Chris—to help fill that void.

One Science Professor, and excellent educator has taken steps to help us all to better understand this subject. Kirk T. McDonald, Professor of Physics at Princeton University has kindly contributed a couple of feature articles in this month’s issue of antenneX. One is entitled “Impedance Matching of Transmission Lines” (the other one is "Small Fractal Antennas" — see list below).

If you want to know more about this elusive subject, or confirm your knowledge—and/or even disagree, you are encouraged to read the above articles. There are some that still disagree with a few things said in Chris’ tutorials, leaving plenty of room for more discussions. I believe experiments are likely to follow and be discussed here in the future as we depart from theory and "cut 'n try" the various methods in a clinical setup.

Moreover, to be brought up to speed on the issues, it would be a good idea to read the threads posted in July 2005 and that may yet follow in the antenna-discussion list. You will be in good company along with some of the brightest minds available. Where else would you have such free access to this level of expert advice? To participate or just read along on some very interesting subjects each month with 2000+ members from all around the globe, you are welcome to join us. To obtain your

Speaking of the many schools of technology that make up part of our audience, compared to standard physics and engineering journals, antenneX is available at a tiny fraction of the cost, with potentially significant surprises—since one never knows in advance what sort of experiments may turn up useful results for theory or practice in the field.

You are encouraged to contribute your thoughts on various subjects to a worldwide audience.

NEW PROGRAMS FOR DOWNLOADS
During the past month, we have added several more programs to the download section in the new Guest Rooms. So, it is a good idea to be registered on the announcement list especially to learn about the free goodies we find and offer like the above.To register on the announcement list, to be notified about more programs and/or articles added to the Guest Rooms, just click here.

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 submissions@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.

Corner Reflectors Revisited Again
Part 4: Variations on Standard Corner Reflectors
By L.B. Cebik, W4RNL

Our next foray into corner reflectors will actually be a sampler of sorts. As we move away from the standard 90-degree reflector with plane sides, whether modeled as wire grids or as a set of rods, the individual topics become more specific, each with a smaller set of design interests. On the other hand each topic might well expand into the semi-complete coverage that I have extended to the standard corner.

Small Fractal Antennas
By Kirk T. McDonald,
Joseph Henry Laboratories, Princeton University

Antennas for hand-held communication devices are necessarily small. However, the performance of small simple antennas (i.e., linear dipoles and loops) is inferior to that of simple antennas whose characteristic length is roughly the wavelength lambda of interest. We discuss whether the performance of a small planar antenna whose conductor fits within a certain square edge area could be improved if the path of the conductor were a fractal pattern.

A Multi-band Trap Antenna
By Fred M. Griffee, N4FG (EE Retired)

This article addresses some designs of an all-band HF trap antenna. The usual problems with bandwidth will be illustrated, especially for 80/75 and 10 meters. Trap losses are addressed and radiation patterns of the individual bands above 40 metes are analyzed. The two popular modeling programs, NEC-Win Plus+ (NWP+) and EZNEC for Windows (EZW+ 4) are used. Concluding remarks address the comparison to the less popular all-band antenna using open or ladder transmission line. Antenna tuner loss is briefly discussed as well.

A New Approach to Poynting Vector Synthesis: Part 4
By Claudio Re, I1RFQ and Federico Vavassori

In the first part of the article series, we decided to check without prejudices the PVS (Poynting Vector Synthesis) rules on an antenna composed from an elementary dipole and an elementary loop. The calculations failed to show a Poynting vector, crossing the E and H fields of the two antennas, at first for the simple reason that the polarization of the two antennas was one opposed to the other (one vertical, the other horizontal). Then, we decided to repeat the calculations rotating the polarization of the loop changing his plane from the XY plane to the ZY plane. The calculations are now developed and the results are shown in this third part of the article series, following two methods: 1) The classical antenna theory; and, 2) The PVS rules. Now in Part 4, we have reached an important practical conclusion about PVS.

Mastering Masts - The Wrong Stuff
By Tom Cox, KT9OM

I never gave more than a few moments’ thought to the choice of an antenna mast, but I should have, as it turned out. antenneX readers may recall that I have a 120-foot tower in my back yard, which used to have two VHF SSB Yagis on top. “Used to” is an important choice of words, here, because those antennas are no longer there. During an ice storm in the first week of January 2005, the mast that held these antennas aloft failed. By “failed” I mean it bent nearly double, whacking the two Yagis against the side of the tower, beating the larger antenna into scrap aluminum and damaging the smaller antenna’s reflector. This article tells my story of Tower woes during a tough winter and my much more thorough research into how best to replace it.

Impedance Matching of Transmission Lines
By Kirk T. McDonald,
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. In this discussion, 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.

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
August 2005 antenneX Online Issue #100