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~ September 2010 ~ Online Issue No. 161 ~

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Read Our Monthly Columns!

Antenna Modeling From The Shack
This is a regular and popular monthly column by L.B. Cebik, W4RNL 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' 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

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!

FEATURE ARTICLES THIS MONTH IN THE LIBRARY
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Adjusting Near-Perfect Broadband Antennas for 80-75 Meters
By L. B. Cebik, W4RNL (SK)

In “Notes on Ribbons, Cages, Parasites, and Lines: Broadband Coverage of the 80-75-Meter Band with AWG #12 Copper Wire” in the previous issue of antenneX, I explored some of the methods for obtaining full coverage across the 3.5 to 4.0 MHz span with a single antenna. I re-examined some further options in a QEX column (“Antenna Options”) that opened some additional possibilities offered by combining broadbanding techniques. Some of the methods of matching via combinations of transmission line proved robust enough to allow the use of ribbon or cage constructs with relative small proportions, instead of the very large dimensions required for direct full coverage by the antenna alone. In fact, we were able to obtain 50-Ω SWR curves with values less the 1.5:1, thus meeting the most rigorous requirements of amateur amplifiers having the most sensitive fold-back circuits.

Practical Antennas: Part 2.11
By Marcel H. De Canck, ON5AU

The ionosphere plays a tricky but an important role to our radio communications, and there is very little we can do about it. But there is plenty you can do about having a good and efficient antenna system. Yes, antenna system, it’s not the antenna itself but the whole part as transmission line, and matching properly the transceiver and the antenna to the transmission line. It is a breath-taking concept that a simple length of wire or rod or tube can transform electrical energy into invisible radio electro-magnetic waves that can cross the space at the speed of light.

How does an antenna system works? Why does the antenna radiate electro-magnetic waves? These questions I heard many times and the answers are not given with few words. Never-the-less, many books and some of great weight and complexity have been written about antennas and many antenna types have been developed and build. Often it is not comprehensive to the layman to fully understand the whys and hows of the radiation capabilities of an antenna and these counts even for the simplest ones like a dipole or a groundplane. Also I often hear many times misconceptions about antenna properties and characteristics. To start with, understanding why and how a simple antenna effective radiates will be explained in a clear view. The dipole is the best antenna to do that and once the secrets of the dipole characteristics and properties are fully understood it will be much easier to have a clear insight of the hows and whys of more complicated antennas.

The first episodes will handle completely about antenna fundamentals mostly with the half wavelength dipole as study example. The dipole is also often a part element of more complicated antennas such as a Yagi and others. In particular for the low frequency bands, the dipole is used by many radio amateurs as transmitting or receiving antenna and its many practical installations and shapes will be fully studied and explained in a chapter later on. In fact many other antenna types will become subject to explanation as the antenna story develops.

NewcomerNotes: Antenna Supports
By Robert Gulley, AK3Q

While we often talk about getting creative with antenna design, sometimes we have to get creative with how we support our antennas and with how they are run. If life were perfect we would all have acres of land upon which to build enviable antenna farms, with one or two antennas for each band we sought to work. Mind you they would all be strung with hardline or super-low loss ladderline, with switching relays, rotors, and crank-up towers. And of course, where useful, full wave loops as needed supported by telephone poles or the like.

Getting creative isn’t just about antenna design and placement, but also about how antennas get supported. I want to talk a bit about antenna supports this time around, and suggest ways in which ordinary items around the house or found at the local hardware store can increase your antenna options. Trees and towers work great, but sometimes they are just not available. Supporting an antenna doesn’t have to be costly—it just needs to work. With this in mind, let’s look at some economical support options, some of which are even free.

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

Do you want an all-band high frequency radio amateur antenna that has real gain, is cheap and is easy to build? This one described can operate on all ham frequencies from 80 meters to 10 meters. It is in the rhombic category but is smaller than most other antennas of that type and likely will fit on your property. Unlike almost every other rhombic, this one has proper beam patterns that uniformly point toward the far end apex on every band from 30 meters to 10 meters, and reasonable omni directional radiation patterns on 80 and 40 meters. It is particularly remarkable; indeed it seems almost magical that the patterns are excellent, without any splitting on every one of six amateur bands.

I have looked at quite a number of rhombics in my 63 years as a ham, engineer, and as a Voice of America advance planner. I was happy to see that for some strange reason everything came together just right with this one special rhombic configuration. The “Magic” Rhombic is simple to build.

The New Super-Delta: Part 2
By Edward J. Shortridge, W4JOQ

The Super-Delta matching configuration is a completely new method of broad-banding radiators for use in some of the wider radio amateur bands, such as the 75/80-meter, 10- and 6-meter bands. The previous article, Part 1, shows the evolution from the Bottom-couple (low impedance), to the Super-Delta. This Super-Delta match provides all of the key ingredients necessary to adjust antennas for the desirable bandwidth, the amount of coupling to provide the best SWR, and the means of matching to a 50-Ohm Source.

It has a very simple configuration, the component costs are quite low, and there are only low loss components involved. The far-field radiation is not impaired in any way by the configuration used, but it does enhance it because of the simple straightforward design.

Part 2 presents horizontal Super-pole antennas for the 75-meter and the 75/80-meter bands mounted at a variety of heights. Illustrations are provided to assist in adjusting the antenna when mounting it. Additionally, Inverted-V antennas are presented at different heights and in a variety of configurations
.

Circularly Polarized Antennas for Ham Radio
By Grant Bingeman, P.E., KM5KG

Circularly polarized antenna system where both the transmitting and receiving antennas are CP can provide some advantages when compared to a typical linearly polarized RF antenna circuit. The reader is cautioned that this report as a series of papers is long, highly technical, and requires careful study. The author hopes the reader will be inspired to experiment with HF CP designs based on the concepts and practical examples described in this series of articles. Circularly Polarized commercial FM and TV transmitting antennas became popular in the 1970s. However CP has seen little use in ham radio applications. This is surprising considering the enormous benefits.
 


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