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Design and Photo by Augie "Gus" Hansen, KB0YH

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Six-Meter Quad Antennas
By Augie "Gus" Hansen, KB0YH

In a previous article (“Starter Antennas for Six Meters”, antenneX, June 2009) I described several antennas that could help those with six-meter capable radios to get on the band quickly for a trial run during the peak skip season. Many of us have at one time or another dipped a toe in the water and have become fully immersed the six meter pool. Others, hearing nothing, have beaten a hasty retreat. That’s their loss.

As noted in the article, when the band opens it can produce some great DX. Well, it has been open very often this past June 2009. The band will continue to be open during much of July, and can provide less frequent but excellent openings any time of year.

The next step for the committed six-meter convert is to install a gain antenna to help out with the weak ones and to provide a way to combat QRM and QRN. This article describes the evolution of a simple quad loop into a four element cubical quad that provides good gain and a reasonable front-to-rear ratio. For this article I have limited the antenna to six meters, but in an earlier incarnation the antenna had a five-element two-meter cubical quad interleaved on the same boom, with all but one element sharing the existing six-meter element frames. The two-meter driver loop had its own small frame and a separate feedline.

Practical Antennas: Part 1.1
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: Yagis and Loops and Quads, Oh My!
By Robert Gulley, AK3Q

Radio Mobile
By Ian D. Brown, G3TVU

Antenna design is a fascinating subject, and many simulation programs are available. These enable new ideas to be tested out on the computer before actually building a prototype. One thing that has been missing is the ability to simulate a designed antenna for its signal path performance over real terrain. This simulation can now be achieved by using the ‘Radio Mobile’ program.

Radio Mobile is a free propagation simulation program written by Roger Coudé, VE2DBE (2). It is based on the Longley Rice Irregular Terrain Model which is useful over the frequency range of 20MHz to 20GHz. Elevation data from the Space Shuttle Radar Terrain Mapping Mission, (SRTM), is downloaded from the USGS site to generate elevation maps of any area, and road maps and aerial photographs can be downloaded and merged as required. Radio Units can be specified for performance and placed where needed on the map, and the characteristics of any Radio Link between any pair of Units examined, complete with a path ground profile.

VHF Scattering by Rotating Wind Turbines:
Backyard Observations
By Bruce L. Cragin, K1THC

Useful observations of the scattering of VHF or UHF radio waves by rotating wind turbines can be made using simple equipment typical of that used by radio amateurs or even scanner enthusiasts. Results obtained here, which are typical of what can be accomplished, confirm and shed light on recently reported features of the time variation of the scattered wave intensity.

Strictly speaking, these are not so much backyard observations as front-porch ones. Eight of the twelve new Gamesa Eolica G87-2.0MW wind turbines that make up New Hampshire’s first commercial wind farm are visible from the front porch of the boyhood home to which I returned earlier this year. Thus, when the topic of VHF/UHF/microwave scattering by wind turbines arose recently on the antenneX discussion list, I was well positioned to undertake some relevant measurements as described in this paper.

Triple Folded Dipole Feed for Yagi Antennas
By Dragoslav Dobričić, YU1AW (Serbia)