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Jack L. Stone
Publisher

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New Issue of antenneX is Published!

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L.B. Cebik, W4RNL(SK)
But Active Contributor


Folks: The new antenneX online issue #197 for the month of September 2013 is ready to read at your pleasure!

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

OUR MONTHLY COLUMNS:

  • Antenna Modeling By L. B. Cebik, W4RNL (SK)
    This column has ended with 147 articles.
     
  • From the Shack By Russ T. Nobs
    Old Timer's Musings- Giving Back
    Amateur radio’s uniqueness as a hobby comes out in many ways, not the least of which is the spirit of giving back to the hobby through mentoring new amateurs. Ours is a hobby which is more caught than taught—which is why sharing what we do, why we do it, and how we do it really requires the "personal touch" of an Elmer. To use a well-worn, but perceptive phrase, we stand on the shoulders of those who came before us. We are either building on the ideas of others, or we are relaying (or learning) from the experiences of others.
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  • Ham WorkShop By various authors
    An open column subject to additional articles.
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  • Propagation By Marcel H. DeCank
    This column has ended with 87 articles.

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  • Antenna Design & Use By Various Authors
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  • The Radio Corner By Robert Gulley, AK3Q
    Radio Accessories
    There is an old saying which goes something like this: “the only difference between men and boys is the price of their toys.” No doubt there is a lot of truth to that adage, but I think it also underscores an aspect of one’s hobbies or interests: whatever one’s passion, it is just that—a passion. The radio hobby is a passion for me, and it stirs within me not only memories of childhood, but also some of the sense of adventure and wonder that is common as a kid. The more you discover about radio the more you want to participate, and that means lots of radios and radio accessories!

    I will readily admit I have more radios than ought to be allowed, both old and new. I also have a lot of radio accessories which make the hobby that much more enjoyable, and so I thought I would share some information about those accessories in the hope that some of them might add to your pleasure as well.

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  • Stone's Throw! By Jack L. Stone, Publisher
    A monthly column covering breaking news, new concepts and products, people making news and introduction of the current month's issue articles and its authors—although not limited to this only.
    This month, the topic is: Flipping Over Solar Maximums

FEATURE ARTICLES IN THE LIBRARY OF NEW ISSUES:

Math, Modeling, Matching and Myths of J-Poles - Part 4
By Edward Lawrence, WA5SWD

I can't claim that I have solved all of the possible issues but I will shed some light on some of the functional concepts of J-Poles and some basic problems I have not seen discussed, including some matching techniques that certainly seem sub-optimal to me.

Most authors omit that we are referring to electrical lengths instead of physical lengths, assuming that the reader knows this already. I will state that this is sloppy writing. If you are telling the reader something you assume he already knows instead of approaching it from the point of view that you are instructing someone who does not fully understand the subject, why are you wasting the learner's time and the publisher's space with only partial information? So, the learning process starts with this 3-part series on J-Poles.

Practical Antennas: Part 6.12
By Marcel H. De Canck, ON5AU

Annother simple array that has been mostly forgotten by hams is the Bruce array, in spite of it has been around since the late 20s. Edmond Bruce took out a patent on this antenna in 1927. A few variations of the Bruce array are illustrated. It is simply a continuously wire one or more wavelengths long, folded so that the currents in the vertical portions are in phase. To ensure that the array is vertically polarized, (at least as a starting principle), we shall feed it at the center of any vertical element. The square loops in the Bruce behave very much like quad loops. As can be noticed in a graphic, it carries the vertical sections large in-phase currents, while the horizontal sections carry the small currents flowing in opposite directions with respect to the center of a section.

Directional Antennas in Small & Noisy Places: Part 1
By Robert Gulley, AK3Q

There is no question that a good directional antenna has numerous advantages over a non-directional antenna, as well as some important disadvantages. My ideal antenna farm would have a good selection of both, with plenty of room for them all. My reality, like many others, is somewhat less appealing. I am on a small lot and in a noisy location. Unfortunately this is becoming more the rule rather than the exception, so the question becomes how do we do more with such handicaps?

In answering this question for my own situation I have found several workable ideas which I hope you will be able to use or adapt to your own circumstances. In this Part 1 I examine shortened Yagi antennas for their directional properties and for their noise reduction capability. They can also be modified to work in relatively small spaces with a minimum of compromise. The goal here is to keep things as simple as possible (no traps or capacitive hats), and to work within realistic limitations. In Part 2, I will suggest some other antenna options, still with the goal of working within a small space.

The "Magic" Rhombic
By Robert C. Wilson, AL7KK & VE7ZKK

Way back about two thousand years ago someone developed a “Magic Square.” It looked like this:
     4 9 2
     3 5 7
     8 1 6
Notice every way you add the numbers, horizontally, vertically, or even diagonally, the sum comes to 15 !!! It works properly no mater which way you add. Well I have a "Magic" Rhombic for you. No matter which high frequency band you want to work it will do the job from 80 to 10 meters. Not only will it radiate on each band but it will always direct your signals in the same direction! Just like the Magic Square this rhombic is also a SQUARE!

Ladder Line Antennas
By Heikki Antman OH7ND

The Yagi-Uda antenna is familiar as the commonest kind of terrestrial TV antenna to be found on the rooftops of houses. It is usually used at frequencies between about 30MHz and 3GHz, or a wavelength range of 10 metres to 10 cm. (There are some obsessional amateur radio enthusiasts who construct Yagi-Uda antennas for the 80 metre wavelength band. This is rather impractical as spacing them from the ground by more than half a wavelength is difficult.) The rod lengths in a Yagi-Uda are about a half wavelength each, and the spacings of the elements are about 1/3 of a wavelength. This puts the overall sizes of Yagi-Udas within the ranges.

Systematic Trap Modeling
By L.B. Cebik, W4RNL (SK)

In some previous notes I developed on traps left me with some unanswered questions. For example, low Q traps appeared to unduly affect antenna gain. Traps using certain forms of linear or transmission-line stub inductors appeared to yield dipole gains above standard full size models. The only way to settle some of these questions is to do some systematic modeling and watch the curves develop.

This brief report is the first step in the process. It models a 10-20 meter dipole using traps that consist of 1.2 microH inductors and 26.92 pF capacitors, resonant at 28 MHz, consistent with common trap practice. As previously noted, the traps are treated as loads on the ends of the 10 meter sections of the antennas. Modeling the traps consisted of calculating the requisite value of the equivalent parallel resistance for each trap Q level for each of the two bands and then inserting the trap as a parallel R-L-C load in the last segment of the outer ends of the 10-meter wire, with 20-meter wire extensions added. The antennas used approximate 3" segments throughout. Hence, trap length is considered for these models to be 3" per trap.

The total antenna assembly was resonated within +/-1 Ohm of reactance on each band for each wire size and level of Q. Selected frequencies were 28.5 MHz and 14.175 MHz, which were considered fair samples of antenna performance with the traps selected.
 

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Hope you enjoy the new issue!

Jack L. Stone, Publisher
antenneX Online Magazine
http://www.antennex.com
jack@antennex.com


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