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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

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