Good judgment comes from experience and experience comes from bad judgment. (Anonymous)

On Speaking Precisely and Reading Accurately
By Jack L. Stone, Publisher

INTRODUCTION
In a recent note to the antenneX antenna discussion group, David Jefferies raises an interesting point that goes far beyond the subject matter of his remarks:

"I have found that when I teach students about the usual terminology of 'free space loss' they immediately start to look for some kind of absorption mechanism in the medium of a vacuum."

"Better terminology is 'divergence factor'. Two antennas, a variable distance apart, subtend a varying solid angle at each other as the distance increases. Thus the second antenna intercepts less of the radiation emitted by the first."

Learning to speak precisely involves more than just stating matters in terms that are conventional to any subject matter. It also involves speaking in ways that will prevent our readers and listeners from being misled—not only by virtue of what we say, but also by the general tendencies of thought that come from their background ideas. Very often, this occurs because we simply are not complete when we express thoughts. Kurt N. Stuba of WorldRadio has long caught many an antenna author in errors. Some of those errors are simply false statements. However, over the years, many of the slips have emerged from stating things incompletely.

Let’s look at a few common examples. Many a backyard antenna builder has learned that an extended double Zepp has significantly more gain than a ˝-wavelength dipole. Without further ado, the builder assumes that the EDZ is a better antenna and proceeds to build one, only to be disappointed in the results. He can work a few places in the world more easily, but many others are weaker than every before. What he heard was incomplete. Indeed, the EDZ has more gain than the ˝-wavelength dipole, but at the expense of beamwidth. We can compare the 80° beamwidth of a dipole with the EDZ’s beamwidth at a little under 40°. Had the reader found the relevant facts, he might have made a different antenna selection.

In another case, the usual amateur standard for a “good” front-to-back ratio in a directional array is about 20 dB. Since a “good” front-to-back ratio makes a “good” antenna, the would-be communicator builds one that meets the standard. He then becomes the control station for a net that requires him to coordinate communications with stations in almost every direction. However, he can hear virtually no one behind the direction at which his beam points. So he spends countless minutes rotating his antenna until the rotator bearings finally burn out. No one pointed out the consequences of a high front-to-back ratio, including when it is most useful and when it may be counter-productive. He had other options, including omni-directional antennas, smaller arrays with lower front-to-back ratios so that he could at least detect rearward stations calling, bi-directional arrays such as the old W8JK flattop, and a number of other choices that would match capabilities to the job at hand.

In many cases, an extra sentence or two would be all that an article (or other text) needs to set an idea into a context that triggers the right kind of reader responses. In other cases, we have to be willing and able to curb inclinations toward colorful speech, impressive associations, and the like in order to be clear. Antenna writers in many casual circles still insist on giving their antennas names that even in the 1930s were considered more cute than descriptive. Hence, we hear of “signal squirters,” “gushers,” and “spurters,” as if an antenna were an oil well or a leaky faucet. Without some comparative data by which to make comparisons with a “standard” antenna, the reader may well assume that the subject radiator is indeed an advance in science rather than what it usually is—an old idea using modern materials. Equally misleading are mis-named antennas, such as the host of “Windoms” on the market. Virtually all of these antennas are varieties of off-center-fed wires that do not operate at all like the original Windom antenna that used a single vertical wire to an asymmetrical T-top. In fact, if folks gave a little thought to the erroneous idea behind the original Windom (namely, the a single-lead feedline was a practical way to feed a horizontally polarized antenna), perhaps they would be less inclined to make the association.

So far we have noted a few cases in which the author has a responsibility to speak as precisely as the situation allows, where precision is not only a matter of choosing expressions that lead the reader in the correct directions of thought, but as well, includes enough information to prevent misunderstandings. However, the reader also has important responsibilities. First and foremost is the need to read both accurately and completely. Reading accurately means remembering accurately. Reading completely means remembering completely. Together, these tasks often mean reading more than just a single article in order to develop the ideas into a network of thought that puts short articles into a context of general antenna knowledge. An article—including the most complete and technical items that you find in antenneX, cannot cover every detail of background necessary to fully understand the performance of an antenna, matching system, feedline, tuner or other part of the overall antenna system.

Perhaps the most insidious influence on modern learning is the tendency to reduce all knowledge into a collection of “sound bytes.” The tendency has become a fully blown way of life in journalism and politics. However, in any technical field, sound bites will not do the job. The reader—at whatever the starting level—must strive for a more comprehensive and inter-connected system of thought about the subject matter. The web has multiple directions. One plane includes the range from theoretical underpinnings to practical applications. Most of the articles in antenneX fall in a broad middle territory, so there is room for expanding the web of ideas even if we do not go all the way back to Maxwell or all the way forward to a specialized application like interstellar communication. Along another plane lie a host of antennas (or other parts of the antenna system) with relevantly similar capabilities. The reader needs to develop a catalog of antennas that “go together,” but at the same time, determine the advantages and the limitations of each one.

In one sense, every antenneX reader shares something in common with every other reader. We are all seeking to expand our knowledge of antennas and antenna systems in one or more directions. The 3 Rs of the old “school Days” song—readin’, ‘ritin’, and ‘rithmetic—come together in challenging combinations for both the reader and the writer. The arena of effective communication has numerous other dimensions: a writer’s understanding of his readers, effective combinations of graphical and textual parts of a presentation, lightening the reader’s burden without reducing the challenge, reading not only the graphic captions, but the full text as well, etc. But for one day, the responsibility of speaking precisely and reading accurately will do as a start in the process.

http://www.antennex.com/guests.html

http://www.antennex.com/guests.html

In view of the above, we have overhauled the nine 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 logins are 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!

This list pertains to those sections with free access now in our new Guest Rooms we have built and fully operating:
• Antenna Science
• Preview Articles
• Software Download
• Antenna Modeling
• From the Shack
• Propagation
• Ham WorkShop
• Stone's Throw!
• Discussion Forums
• Patents (new room under construction)

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:

Get you login all setup now at this URL:
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We've really tried to make it easy while still fending off the bad guys, i.e., pirates!

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.

If you still need help or have questions about our login areas, check this page first:
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.....and, you can always get help here if you still have further questions:
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The new Antenna Discussion List is a infinite fountain of ideas making it a great "watering hole" for exchange of ideas, questions and answers on a wide range of antenna-related subjects. You will be in good company along with some of the brightest minds available. Were 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 Antenna-Discussion Archive | To Join Discussion List |

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

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AN INVITATION TO CONTRIBUTORS
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.

To see details of our writing guidelines, please look at: Writing for antenneX

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IN THIS ISSUE
We again include many fine articles by our great writing team from around the globe. Now, allow me to introduce this month's line-up of content:

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OUR MONTHLY COLUMNS (plus this one you are reading by yours truly):

• From the Shack By Bill Miller, KT4YE
  Of Sailing Ships and Antennas
  In the age of discovery, economic and political pressures forced the development of more robust long-range ships. Builders responded with cargo vessels featuring wider and deeper holds. To protect cargo and holdings, builders made warships resembling nothing as much as floating fortresses.
  
  Antenna design and construction – in an era wherein a Personal Computer is obsolete before the warranty has expired – must be considered as “mature” by anyone’s standard. In this article, let’s consider some benchmarks in antenna design.

• Antenna Modeling By L. B. Cebik, W4RNL
  The Dipole and the Coax
  The most usual way to feed a resonant dipole uses a simple coaxial cable. Most basic handbooks and texts recommend that the system builder insert a common-mode choke at the feedpoint--between the dipole feedpoint terminals and the coaxial cable. Readily available forms of common-mode choke include a transmission line transformer with a 1:1 impedance ratio and a ferrite-bead collection following the designs proposed initially by Walt Maxwell (W2DU). In either case, the device establishes a compatibility between the balanced feedpoint of the dipole and the seemingly single-ended construction of the coaxial cable.

• Propagation By Marcel H. de Canck, ON5AU
  Ionosphere Properties and Behaviors - Part 1
  In this series Marcel digs a bit deeper into the various ionospheric properties, characteristics and behaviors. These can be in favor or not in favor to our wave propagation and be the cause of strange but often interesting propagation options, modes, and paths. In this month’s issue I take a closer look to the signal absorptions and the gyrofrequency property.

FEATURE ARTICLES IN THE LIBRARY:

Long-Wire Antennas Part 2: Terminated End-Fed Long-Wire Directional Antennas By L.B. Cebik, W4RNL

In Part 1 of this series, we examined some fundamental properties of both center-fed and end-fed unterminated long-wire antennas. Without the kind of data that our basic investigation showed, the terminated version of the end-fed long-wire antenna might seem more odd than natural. As we move from the symmetry of an unterminated antenna, sometimes called a "standing-wave" antenna, to the asymmetry of the patterns of a terminated wire that is the same length, the assimilation of the nature and growth of both elevation and azimuth lobes will hopefully carry over to naturalize the new patterns and performance values. The mark of success in the process might be that we are able to predict in very general terms "what happens next."

An 11-Element 2-Meter Yagi-Uda Beam for Backpacking by Robert K. Zimmerman, VE3/NP4B

A folding Yagi is very handy for backpackers and bikers. Here we go one step further by making an 11 element (gain = 10.8 dBi) Yagi that rolls up for compact transport. Rather than using a Gamma match (which is mechanically complex) we feed the driven element offset from the center directly with 50-W coax, making a robust lightweight feeding system. The completed antenna is shown in the article. The antenna elements consist of ˝ inch wide aluminum (or copper) adhesive tape strips on a woven polyethylene fabric tarpaulin. There is no boom, but rather the antenna is unfurled and hung “hammock style” between trees or other supports. As such, since the antenna cannot be readily rotated in azimuth, it is important to carry a map and compass so as to aim the beam at your desired target.

A Backyard Random Wire Antenna By Fred M. Griffee, N4FG (EE Retired)

The subject antenna analysis will address a wire antenna, installed and supported by the available trees within our property boundaries. Surprisingly, it will turn out to be somewhat of a distorted horizontal delta configuration with one side missing, only because the wire would travel over power entry lines to our house. It will be shown that even with a fixed length of transmission line, the associated balanced L-matching network will have little difficulty in providing a conjugate impedance match, and that the overall antenna system efficiency will be greater than 90 percent, even for the 160-meter band. The actual antenna installation will be done and measured, the results being made Part II of this article series. Available instrumentation for comparison to the theoretical predictions will be used.

Magnetic Loop Antenna for Short-wave Listening By Alexander Krist, KR1ST

Now that we’re on the downward slope of sunspot cycle 23 you may have noticed that some of your favorite broadcast stations don’t come in as strong as they did a few years ago. This is especially apparent on weaker DX stations. The whip on your short-wave receiver used to be sufficient to pull in some good DX, but now you find yourself looking for something better. Maybe you have been thinking, or even have already tried, putting up a wire antenna. This may be a great solution if you live in a reasonably quiet area, noise wise, and your short-wave receiver doesn’t easily overload in the presence of strong signals. Perhaps you live in an apartment or are situated where installing a wire antenna is simply not feasible. Or maybe you’re looking for something that offers a bit more mobility so you can take it into different rooms of your house. Consider the small single turn magnetic loop antenna if any of the above situations apply to you.

Horizontal Polling Arrays L. B. Cebik, W4RNL

Rotators are slow-moving devices--advisedly so, because spinning an antenna at high speed can induce large stresses, even at VHF and UHF frequencies. The chief stresses will be due to acceleration and deceleration whenever we start or stop the system. Moreover, rotators are generally not built for continuous operation. Rather, they prove to be most durable when used sporadically to move a directional antenna toward a desired communications target. The rotator problem presents a challenge to the growth of PSK and related digital operations in the VHF region. Activity on the low end of 2-meters has increased, and ranges that are impossible for voice and improbable for standard CW are proving to be routine for PSK. Skip Teller, KH6TY, reports regular contacts in the 300-mile range on this mode using moderate power and relatively standard modest beam antennas. The difficulty is that the digital transmission may come and go faster than the operator can move a beam to detect, let alone decode, the signal. The solution may lie in using a polling array.

Experimental Measurement Uncertainties David J. Jefferies

What are measurement errors (sometimes called "uncertainties"), and why are they important? Except in straightforward counting situations, there is always a difference between the measured value of a variable and the true value. This difference is called the "error". By the nature of an error, it must be an indeterminate quantity, or an "uncertainty", for if we knew what it was precisely we could adjust for it and we would then know the true value precisely. The value of an error can therefore only be estimated; it cannot be known precisely. A measurement, which does not report the likely range of possible errors contains limited information, for we can be quite sure that the true value differs from that reported and we have no idea of the possible size of this difference. Uncertainties are sometimes quoted as a fixed number at a 90% confidence level, or some such figure. There are established procedures for estimating such figures; a useful site is the National Institute of Standards and Technology (NIST) in the USA.

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-

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Best reGARDS, Jack L. Stone, Publisher
jack@antennex.com
June 2006 antenneX Online Issue #110

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