Adjustment Sensitivity of Small 15-Meter Band Attic Antennas
By Grant Bingeman, P.E. KM5KG

This article presents a simple and effective method for tuning any antenna in the least amount of time and with the least amount of frustration. An understanding of antenna impedance behavior during the design phase is developed using specific examples. This understanding will be applied to the physical adjustment process during antenna installation. The subject is a bit more complicated than might at first appear to the casual antenna enthusiast. Therefore a simple metric to quantify relative adjustment sensitivity is presented so that the reader may compare antenna designs fairly.

Because an attic antenna is typically limited in size, adjustment becomes more of an issue since 1) electrically small antennas are more sensitive to their surroundings, and 2) a small dimensional change can create large impedance changes. In other words, electrically small antennas can be touchy, which means their impedance changes rapidly.

Practical Antennas: Part 4.05
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 an episode later on. In fact many other antenna types will become subject to explanation as the antenna story develops.

NewcomerNotes ~ Back to the Basics: More Wire Antennas
By Robert Gulley, AK3Q

Simple Building and Tuning of Traps
By Martin Steyer, DK7ZB

THE MAGNETIC DIPOLE:
A New Theory for the Radiation Resistance of Ferrite Rod Antennas
By Alan Payne, G3RBJ

A loop or coil can be used as an antenna, but the received signal will be weak unless the coil is very large. However the signal from a small coil can be enhanced considerably by inserting a ferrite rod into it, because the rod captures a volume of the incident electromagnetic field which is much larger than itself, and concentrates this into the loop. This capture effect is not unique — a conventional wire dipole antenna also has an effective area vastly larger than its physical area.

In the conventional theory this enhancement when the ferrite is introduced is considered to be due to the permeability of the rod (which is related to the ferrite permeability), and so the ferrite antenna is seen as a coil antenna with an enhanced effective area. However it is shown later that this idea leads to an erroneous theory, because the ferrite rod is in fact a magnetic dipole, and the coil merely provides a means for detecting its flux. But we begin by testing the accuracy of the conventional theory.

Circular Nomograph for Converting Between Field Intensity
and Signal Level across the Antenna Terminals
By Harold Kinley, WA4GIB