THE STRING ANTENNA

"A new idea is first attacked as absurd; then it is admitted to be true, but obvious; finally, it is seen to be so important that its adversaries claim that they themselves discovered it."

William James: Pragmatism - a new name for some old ways of thinking.

The string antenna, as far as the authors are aware, is the first practical application of an unusual property provided by the new String Theory of the physical universe. Although most of the technical underpinning is not yet widely understood other than by an elite group of theoretical physicists, non of whom are hams, it was nevertheless decided to make public the initial practical experiments of the string antenna in order to stimulate and encourage investigation and experimentation in this field. The first part of this article provides a short summary of the theory which led to the string antenna followed by a report of the preliminary tests and results of the field trials.

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Albert Einstein spent the last 30 years of his life in an unsuccessful attempt to find a unified field theory - a single theory that would explain the structure and working of the physical universe. What drove him in this quest was that at that time there were two theories of the universe that were incompatible with one another.

At one pole sat his general theory of relativity which deals with the universe at the macroscopic level with enormous objects such as stars and galaxies and the immense distances between them. At the other pole sat quantum physics which deals with the microscopic world of exceedingly small atomic particles. These two views were mutually incompatible. The equations required to solve problems in one gave totally wrong answers when applied to the other. The new String Theory, or more precise, Super String Theory, provides an explanation that describes both opposing theories in an inclusively coherent and unified manner. The scientists who developed String Theory succeeded in eliminating the disagreement between the two conflicting theories. String Theory, whose origin dates back to about 1975, is still being developed and is currently being modified by what is called `M' theory. But the main portions of String Theory which we will deal with are in place and have been verified.

It is one consequence of this theory that was the impetus for the development of the string antenna. However, before providing a description of the antenna it is desirable to gain some insight into the background from which it evolved. Relativity gave us bizarre notions of the universe such as space curves and time warps. String Theory gives us equal if not more fantastic concepts that are so far removed from our everyday experience that they prove to be incomprehensible to most humans. And therein lies a problem. A description of String Theory, which is best described mathematically, is restrained and bounded by the limitations of language as well as by the familiar experiences of our everyday surroundings. It is as difficult to verbally describe the details of String Theory as it is for the mind to comprehend, let alone visualize, how the universe is put together and how it works. Notwithstanding these obstacles it is necessary to obtain some knowledge, albeit of a most rudimentary sort, if we are to understand anything at all about the string antenna.

It has been experimentally verified that all matter is made up of three basic components. They are electrons, protons and neutrons. It has also been experimentally verified that there are four basic forces in nature. These are the gravitational, electromagnetic and the weak and strong forces. The weak and strong forces are found and operate only at the subatomic level. The basic constituent of the electromagnetic and the strong and weak forces is the photon. A photon is characterized as a packet of energy. On the other hand the basic constituent of gravity is the graviton although it's existence has not yet been verified experimentally.

There are, in addition to those mentioned above, other components of the universe such as gluons, mesons, bosons, neutrinos, etc., but it is not necessary to invoke them for the purposes of this article.

String Theory postulates that all of the component parts of nature, particles and forces, at the most basic level, are made up of what can best be described as  one-dimensional vibrating strings without mass. One dimensional because they are infinitely thin - they have no thickness as such. The strings are the absolute basic constituent of all matter particles as well as the forces they exert and to which they respond. The strings can be open ended but more usually have a closed circular shape. They spin and vibrate in various modes and at various frequencies. The mode and the frequency at which they vibrate determines whether they constitute a quark, an electron, a photon, or any other matter particle or one of the force particles. In this way, all observable aspects of the universe are readily explained. Everything is reduced, at the fundamental level, to these vibrating strings.

What are the strings made of? That is an invalid question. If it had an answer then whatever the answer provides would be the most basic component of the universe. But the strings themselves are the most basic component and so to be strictly correct, the answer would have to be 'nothing'. However, that is a perplexing response and one not likely to instill satisfaction. Perhaps the best we can do is to say that strings are pure energy.

In nature there is what is called a `dual' or a `duality'. Fortunately there is a dual in a subject close to our experience - which is electronics. We will describe a dual using an electronic example. Assume that we take a 20 ohm resistor and a capacitor with 150 ohm capacitive reactance at a certain frequency and connect them in series. Then we place them in a sealed box with just the two leads sticking out. Next we take a 1145 ohm resistor and a different capacitor with 152.66 ohms reactance and this time we connect them in parallel and put them in a sealed box with just the two leads sticking out. Finally, we use an impedance meter and connect it, in turn, to the two leads sticking out of each box. Although the component values in each box are completely different, as is the connection, the impedance will measure exactly the same for each box, 151 ohms, and with identical phase angle. It will not be possible to determine which box contains the series connection and which box contains the parallel connection when we make the impedance measurements. When two networks exhibit this relationship - provide the same result - they are called duals.

String Theory also exhibits the attribute of duality but it is more properly called Mirror Symmetry. String duals have to do with what are called `winding number', `vibration number' and `Planck length' and several other factors. These, in turn, have to do with the string length and how they wind and bend themselves around and in an abstract multi-dimensional space. It is here that we will not pursue the internal details of the theory any further. It is not essential to the development of the string antenna to delve into the more esoteric parts of the String Theory. Suffice it to accept the existence of the dual nature of strings which has been predicted and verified mathematically.

The dual nature of the string structure makes no distinction between two different circular string sizes with radius dimension R and it's reciprocal 1/R. The theory asserts that any experiment will yield the exact same results when applied to dual string structures with arbitrary size R and it's dual, or mirror size, 1/R. In other words, all physical phenomena has a dual structure. We are free to choose either part in our experiments because either part will provide the same result as the other. It is this concept that is the takeoff point for the string antenna.

When the concept is applied to radio antennas the thinking is as follows. If a 14 megahertz half wave dipole antenna is nominally 33 feet long. Then it's reciprocal, 0.03 feet, or 0.36 inches, will yield the same result. A comparable antenna for the 40 meter band is 0.176 inches and a 75 meter antenna is 0.09 inches. Each antenna length, either the full sized one or it's drastically shortened dual, will provide the same identical results.

Intrigued and inspired by this relationship, two engineer/hams, Dr's Jorge Soto and Gustavius de Groot, on a sabbatical from Radio Instituto di Emisiones, Sao Paulo, Brazil, undertook, during the early part of 1998, to develop and test a dual string antenna configuration and determine whether theory would prove itself in practice. Accordingly, a 14.050 megahertz, half-wave dipole antenna was fabricated. It was 0.36 inches long overall using 20 gauge bare copper wire and carefully measured at 0.18 inches per leg. The two legs were conductive epoxied to the ends of an low loss parallel wire transmission line made of 26 gauge enameled copper wire with 0.25 inch spacing center-to-center. The two dipole leg ends were carefully positioned as close as possible to each other at the feed point using a piece of 2.5 mil Teflon tape as an insulating medium between them.

The problem of feeding the antenna was particularly challenging. The free space radiation resistance is 1/70 = 0.0143 ohms. This low value of radiation resistance precludes conventional matching techniques. Accordingly, the problem was solved beginning at the `other end' so to speak. A 100 watt transmitter was constructed using a 12 volt DC supply which, allowing for a 2 volt transistor saturation voltage, calculates to 10 volts as the applicable voltage to use in the equation v²/2p. The equation is the required power transistor load resistance which calculates to be 0.5 ohms where p is the power output in watts. A 6 to 1 turns ratio low loss transformer was used to step the resistance down 36 times to 0.014 ohms. A full wave low loss open wire line, as described above, was used between the antenna and the transformer. The load on the transmitter is thus 36 X 0.0143 which is 0.515 ohms and sufficiently close to the required 0.5 ohms. Although not perfect, this was considered acceptable under the prevailing circumstances. The transformer was wound on a 150-2 Amidon toroidal core using 20 gauge enameled wire with a Teflon sleeve. The primary was 6 turns evenly spaced around the core and the secondary was 1 turn. Subsequent readjustment of the DC supply voltage to impose a load of 0.515 ohms did not result in any change in system efficiency that we could detect.

The test antenna was secured to the top of a 60 foot crank up tower and tested on the air on July 4, 1998. The initial results were dramatically breathtaking. The Marconi/Newcombe 623-E Field strength meter, parked approximately 500 feet away, showed an increase of 2.6 dB compared to a full size 34 foot dipole comparison antenna at a 35 foot elevation. The antenna was then lowered to the same height as the 34 foot dipole. The dual antenna measured the identical signal strength as the full size dipole. This part of the experiment verified that the `dual' nature of the two antennas is correct as predicted by the theory.

The R and 1/R antenna dimensions become identical at a frequency of 468 megahertz. Above this frequency, string antenna lengths become progressively greater than conventional antennas as the frequency is increased. Thus string antennas above 468 megahertz do not offer the 1/R dimensional advantage.

The antenna was rotated about the vertical axis in order to measure the radiation pattern. There were no surprises here. The pattern is the classic figure 8 pattern associated with a conventional half-wave dipole in the horizontal or azimuth plane. In spite of our desire to measure the current distribution along the antenna we were stymied due to the difficulty in accurately measuring such a small structure with the instrumentation at hand.

It has no doubt occurred to many of you whether the same dual techniques can be applied to directional gain antennas such as the popular Yagi and Quad configurations. The answer is in the affirmative. However, the feed requirements have proven to be intractable thus far and we have not yet succeeded in developing an acceptable solution to this problem.

Extreme precision must be applied to the mechanical construction of string antennas. Sloppiness in measurement and assembly will not do. If you are motivated to experiment with a dual antenna, obtain suitable precision tools and good quality magnifying optics to help you. Do not be discouraged if your initial attempts seem unsuccessful. Fabricating a string antenna is easier said then done. Learn from your failed attempts and persevere.

The smallness of the antenna and the stringent accuracy requirements are particularly suitable for printed circuit fabrication and the developers of the string antenna would like very much to encourage experimentation along those lines - particularly at the lower frequencies where sizes become progressively shorter as the frequency is lowered. We are especially receptive to any and all feedback pertaining to your results.

Also be aware that feeding the antenna as described demands that the matching transformer be connected directly to the transmitter final stage transistor collectors - a requirement that demands surgery inside your rig unless you build a separate power amplifier for purposes of experimentation.

A hint of the small size advantage of the string antenna could perhaps have been foreseen as far back as the mid 1920's when Louis de Broglie, Irwin Schrodinger; et al., postulated and verified the dual nature of electromagnetic radiation as having both wavelike and corpuscular attributes. Prior to that time the corpuscular nature of radiation was not yet known and so antenna technology was developed utilizing the wavelike form of radiation. In this mode, antennas necessarily had to conform to lengths substantially in close agreement with the wavelength of radiation. Consequently the particle nature of radiation was completely ignored as antenna technology continued to develop. The result is that today all antennas are sized according to the operating wavelength. The string antenna utilizes the particle nature of radiation in which wavelength as such has no part. It is by exciting subatomic particles, the string photons, that the string antenna launches radiation into space. Wavelength long metallic structures are not needed because it is not the wavelike nature of radiation that is being used. It took the development of String Theory to direct attention to the corpuscular or particle mode of radiation by virtue of the dual phenomena that allowed miniaturization of the structures.

It has no doubt occurred to you why such a simple technique has not been discovered experimentally or accidentally and exploited prior to this disclosure. We believe that it is a simple case of misdirected inertia. Hams have built and tested small antennas but not to the scale of the 1/R dimension. Vertical mobile antennas perhaps serve the example best. As an 80 meter mobile vertical antenna becomes shorter and shorter serious difficulties appear regarding matching and radiating efficiency. The antenna becomes prohibitively useless at around a nominal five or six foot length. Hams have simply not taken the shortening beyond that point to the tiny dimensions specified by String Theory. Based on their experience with progressive shortening, to continue the reduction would have seemed exceedingly absurd.

In spite of the extensive work we have performed on the string antenna, there are many questions of a perplexing nature to which we have no definitive answers. Some of these concerns can be gleaned from this report. The field is wide open and begs not only experimentation but a sound theoretical foundation. It is our hope that the ham community will contribute in those areas, as they always have, to this strange and exciting new field.

Anyone duplicating these results should be aware that all of the precautions such as near field radiation intensity, RF in the shack, susceptibility to RF burns due to inadvertent contact by people and/or pets, etc., still apply.

NOTES

1. For a good introduction to String Theory, see `The Elegant Universe' by Brian Greene. Published by Vintage Books, especially chapter 10.

2. Superstrings by E. David Peat. Published by Contemporary Books, Inc.

3. The Big Bang by Joseph Silk. Published by W. H. Freeman and Company. Page 410.

4. Visit http://www.geocities.com/CapeCanaveral/launchpad/8959/super.html and http://www.lassp.cornell.edu/GraduateAdmissions/greene/greene.html. There are also other web sites you can visit for interesting information on StringTheory. Do a web search for the latest ones.

5. Some preliminary but as yet inconclusive work has been accomplished using string versions of broadside and end fire antenna arrays including Beverage, Sterba curtain and Rhombic configurations. However, it would be premature to release experimental information that is incomplete at the time of this writing.