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How Does an Antenna Work?

1.1) Introduction

 If you have ever wondered, how does an antenna work? You have come to the right place to find out but it will take more than just a few minutes to absorb all of the following information and the full explanation comes in several articles, some yet to be published. You will need a clear head, an open mind and possibly be ready to re-learn some very basic facts. The study of antennas is traditionally a highly mathematical subject that is based on illogical concepts that most people cannot get their head around. The reason that it is so difficult and confusing (apart from the complexity of the maths) is because some, but not all, of the classical accepted antenna theory is in either inherently wrong, or incomplete. The major problem being that the whole concept of calculating antenna performance is based on a theoretical antenna current distribution which is itself based on the old transmission line 'standing wave' theory which is fundamentally incorrect. Even the alternative Method of Moments calculation of current distribution does not give the correct results and does not help at all in the understanding of the radiation mechanism. There are also several other serious misconceptions in classical antenna theory that will come to light as this study progresses.

1.2) Present Understanding

A typical description of how an antenna works will start of with a diagram, similar to figure 1 (see description at bottom of page), of a dipole and the statement that the simplest form of antenna is a half wave dipole.

Figure 1. Composite Diagram of Antenna Current Drawings

[diagram of current distribution in a dipole]

 

 Firstly, it is difficult to accept that a dipole is simpler than a monopole when a dipole is obviously mechanically more complex. A better statement would probably be that the mathematical analysis for the dipole is simpler than a monopole. Even the name Dipole is slightly misleading when it is clearly obvious that it is two λ/4 monopoles back to back and that they will behave as per two λ/4 monopoles, although possibly with different phases at the ends, which could potentially be regarded as two poles but they are a 'duplication' not opposite poles (like North and South) as will be revealed later. The indication of 'standing wave' current in the drawing of course does not represent the actual currents present as will be seen in the antenna current distribution article and also the reference to 'standing waves', the theory of which is itself in error, does not help to explain the functioning of the antenna.  The drawing also raises many other questions, such as the implications of the phases indicated and current directions.

 It appears that the dipole was an early form of antenna that was ideally suited to an open transmission line with a balanced output. The Tx lines would be fed out of phase so that their radiations cancelled out and there was very little total overall radiation measured from the Tx lines themselves. The inherent impedance of the lines was higher than that of a coaxial cable but this matched the dipole input very well. As the two individual wires of the Tx line arrived at the antenna close together it was easy to connect them to the dipole centre. In all, it was a very simple way to make a transmission line and antenna. However, by studying the drawing of the resulting phase with both currents in the antennas flowing in the same direction and the right hand antenna with a positive charge and the left hand one with a negative charge, it seems that the phasing of this theoretical antenna would cause a signal cancellation at a distance and render the antenna useless. There is a fundamental error here that will be revealed in one of the latter articles.

 The errors in the classical antenna theory are such that the design of antennas has hardly progressed at all in the last fifty years. It is virtually a pseudoscience and a quick glance at Wikipedia (http://en.wikipedia.org/wiki/Pseudoscience)  will reveal that "In 1978, Paul Thagard proposed that pseudoscience is primarily distinguishable from science when it is less progressive than alternative theories over a long period of time, and its proponents fail to acknowledge or address problems with the theory". Cruel as that may sound, this description seems to fit antennas quite well as it is noticeable that antennas have not improved in the way that the rest of communication equipment has and there has certainly been little progression in antenna theory. Not that we should decry the amazing intellectuals that have given us the theory that now exists.  How on earth did they work out anything with the limited facilities available beginning over a hundred years ago?

1.3) Study Structure

 This study will be presented in a series of self contained articles which have information from text books, graphs, measurements, experiments, formulas and calculations that expose the simple reality behind antennas that has been obscured for over a hundred years. This will be in much the same way as standing waves have been disproved in our previous article. There will also be another related article on Electrons which cannot be proved so easily and is kept separately as discussion and a theoretical model only; this will be released once all of the other antenna articles have been published and debated.

We will be publishing articles in slow succession and if you disagree with anything, fine! Please use the Contact Us facility and explain what we have wrong and why. Please do not just refer to an opposing statement in a text book, but give definite argument, experiments and evidence to back up your statements. Your email will be published if you request it, at the end of the appropriate article, even if it is a direct criticism of our findings.

 Right, now that such bold statements have been made it is time to start the articles. The first one in this series is on Antenna Current Distribution and is taken in easy to understand steps. The second article in the series covers voltage distribution which leads to a comparisons between actual antenna current and voltage distribution, with traditionally accepted antenna current and voltage distribution. If you do not agree with anything in any of articles please let us know! When there are no objections to the latest  article published for a reasonable period, then the next article on antennas will be published and this page will be up dated.

Continue to Antenna Current Distribution

How Does an Antenna Work Index

Technical Article Index

William J Highton

First Published 6/4/2014

Last Article Added 16/7/2015

 

Figure 1 is constructed from several text books including:-

The Services Textbook of Radio Volume 5 Transmission and Propagation by E.V.D GLAZIER and H.R.L. LAMONT, London, HER MAJESTY'S STATIONARY OFFICE 1952. page 283 fig. 10.1

ANTENNAS Theory and Practice by Sergei A. Schelkunoff, John Wiley & Sons 1952. page 238 FIG. 8.5