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  Founded in 1988  
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Read Our Monthly Columns!

Antenna Modeling From The Shack
This was a regular and popular monthly column by L. B. Cebik, W4RNL (SK) Because computerized antenna modeling has become widespread, and its popularity as a design tool continues to increase, this series is devoted to helping readers get the most from the design software used. The articles focus upon the use of NEC and MININEC, along with useful adjunct software as well.

This column is primarily for "Guest Editorials" to provide a podium for our readers to voice their opinions to the rest of the world too. This is a chance for readers to get on their "soapbox" and speak about antenna and radio-related subjects. Don't miss these interesting views about anything and everything about radio and antenna systems! Now, what have YOU to say??

Ham WorkShop

Stone's Throw!

Ham WorkShop, is also another regular monthly column  filled with a variety of "RADIO-STUFF" of value to almost everyone in amateur radio from Novice to Extra and those just beginning to take up this special hobby. This includes subjects, but not limited to: VHF, choosing the right antenna, coax cable, small to mid-scale construction projects in a practical manner, use of test equipment, etc. It is also meant to help readers become more familiar with the technical jargon and the fun side of radio. jls.jpg (2372 bytes)Stone's Throw! a monthly column by antenneX publisher, Jack L. Stone, among other things, is to keep the readers informed about our progress, new developments, plans for the future, and to introduce the authors and their subjects each month. Also, our main slogan around here is "we aim to please", so this serves as a place for the readers to tell the publisher what is wanted or at least make suggestions. Just remember, the publisher is only a Stone's Throw away! Go in for a visit and read this month's column.

Propagation

Antenna Design & Use

marcel.jpg (2142 bytes)Propagation another monthly column by Marcel H. De Canck, ON5AU of Belgium. Signal propagation is a subject that is one of the most basic ingredients of radio and is something everyone in radio should know about in order to maximize communications in the most effective way. It’s not enough to have the best equipment and the best antenna if you are trying to send out a signal against a brick wall. Conversely, one may possess a very crude rig, running low power, but yet transmit/receive a signal to great distances with ease, simply by making use of a thorough knowledge about how signal propagation works within the environment. Follow this column and learn more about propagation! The author of the monthly column Antenna Design & Use is Justin Johnson, G0KSC who does in fact design and install antennas in many parts of the world. He's a real hands-on expert with years of experience in this field. Following this column will be helpful especially to those pondering a new antenna project. Examples of how to model the designs will appear at times as well. There is something here for just about everyone wishing to know more about how antennas are created, tested and used.

The Radio Corner
By Robert Gulley, AK3Q

The Radio Corner is a monthly column by Robert Gulley, AK3Q, devoted to exploring radios and radio-related topics of all stripes. The radio is the other essential half of the antenna connection, and the possibilities for both are almost endless. From antique radios to high-tech Software-Defined Radios, and everything in between, each edition of The Radio Corner explores radios, software, hardware and almost anything radio-related. Amateur, shortwave, digital, utility, broadcast, military and civilian aeronautical radio are just some of the topics covered by Robert, and no doubt readers will want to build even more antennas after exploring these facets of the radio hobby!

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Babinet's Principle for Electromagnetic Fields

In optics, Babinet's principle for complementary screens is that the sum of the wave transmitted through a screen (usually considered to be "black" except for its apertures), plus the wave transmitted through the complementary screen, is the same as if no screen were present. An electromagnetic version of this principle was given by Booker, who considered perfectly electrically conducting screens and argued that the electromagnetic fields in the case of the complementary screen (labeled with a ′) that appear in Babinet's principle should be the dual fields -B′ and E′ rather than the nominal fields E′ and B′.

Practical Antennas: Part 8.07

The driver elements position in an interlaced multiband Yagi, either using coupled resonator system or direct-drive feedline, plays a certain role. When moving a driver element position, also the other elements related to that Yagi driver element have to move. Thus, the spacing between all the multiband elements are shifted and changed. Also the mutual couplings between any elements become different. Any changes influence the antenna performance, either minor or significant.

To investigate the impact of these element position moves, I will make a study with an overall design. This dual-band design begins with a 3-element wideband 15-meter Yagi capable of matching a 50-Ohm main feedline.

Direction-Finding: The Sport of Hams!

I must confess to getting rather excited. I know it is early days yet, but before long next September will be here and the seventeenth USA and Ninth IARU Region 2 ARDF Championships will be underway right here in my home town. Our club is going to be the main host for this event, as we have two nationally known champions as a part of our group. I am particularly looking forward to seeing (and hopefully discussing) antennas with some of the participants - what they use and why.

Direction-finding is a very special niche of amateur radio, not only because of the international sport it has become, but also because the techniques used often emphasize opposite aspects of our normal antenna design. This is instructive not only for locating the "fox" (or interference or an offending transmission), but also for our testing and design of everyday antennas.

Links and Tips from Around the Web

There are so many great resources around the web (like antenneX!) one can spend more time exploring than actually operating. I try to find a good balance in that my first love is amateur radio, but I am not so set in my ways I cannot find great value in the multitude of resources available to us today. I have some cronies who will simply not get on the Internet, or even use a computer. "Paper logs are good enough!" they say.

This time around I thought I would share some of the more useful resources I have found, with the hope at least some of them will increase your enjoyment of this great hobby.

Notes on Fat-Wire Dipole Convergence: MININEC, NEC-2, NEC-4

A standard dipole at HF made from commonly used materials can be accurately modeled in any of the NEC-based programs using minimally recommended segmentation. Convergence testing (increasing the segmentation density) confirms the accuracy of the model for virtually any purpose the model might be used.

Similar behavior is often expected from dipoles of increasing diameter, for example up to 1' at 14 MHz. 2 * PI * radius (circumference) / wavelength must be much less than 1, a condition easily met by this large dipole. MININEC prefers the largest minimum segment length to diameter ratio: 1.25:1. This condition is easily met if the segmentation density is about 40 per half-wavelength or less.

Even within program limitations, however, the modeler encounters some interesting program-to-program variations that are worth noting. They may not be operationally significant in terms of model reliability. Still, they will increase our awareness of program tendencies and trends, thus enabling the modeler to view a certain set of progressions as either expected or unusual.

Multielement Arrays: A Mutual Attraction Part 2

Multielement arrays are an elegant solution to adding directivity to our signals. There are many, many different designs, and there are even the ones yet to be developed. As noted in Part 1 of this series Multielement Arrays work on the electrical principle of coupling, typical referred to as driven arrays or parasitic arrays. They may also be broadside arrays, end-firing arrays, and bi-directional arrays. With this much variety there is real room for creativity, while still being able to utilize the laws of physics. Let's look at a little more theory and then look at some of these antennas to see just how they are designed.
 


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