Friday, September 30, 2011

Introduction to the EH Antenna

Introduction to the EH Antenna

Welcome to and the wonderful world of EH Antennas. Those of you who have visited this site previously will find major changes, primarily deletions. Diversified Technology Inc. (DTI), based in Ridgeland, Mississippi, has obtained a license to develop, manufacture, and sell EH Antennas for all applications, excluding AM broadcast and ham radio. In conjunction with selling the license for three of his EH Antenna patents to DTI, Ted Hart has agreed to work with the company as a consultant to develop the EH Antenna for specific applications.
Military tests have proven that the EH Antenna, which is much smaller than standard antennas, significantly enhances the communications range of radios. The military is now funding DTI to develop EH Antennas for various military radios. The significance of this new antenna cannot be overstated; the Director of Research for the Department of Defense has even declared it to be a “quantum leap in technology.”
The EH Antenna has very broad applications. For example, a small loop antenna modified to be an EH Antenna provides a significant enhancement to RF Identification (RFID) systems. In addition to increasing the range to the transponder (tag), it allows a large number of tags to be read simultaneously. The modification of the loop antenna produces a radiation pattern which is orthogonal to the loop. As there is no reactive field, the tags are immersed in a true radiated field. This allows more freedom in the positioning of the transponders. In contrast to older systems which required tags to be parallel to the axis of the conventional loop antenna, practically any orientation of the EH Antenna and the tags will provide maximum magnetic coupling.
The first commercial EH Antenna for AM broadcast is now operational in El Salvador. There, as in so many places, land acquisition presents a significant problem. In many areas the amount of land needed for conventional antennas requiring large ground radial systems is cost prohibitive. Other areas lack sufficient land that is flat enough to position radials. Of course, the economic factor is paramount; thus the unique characteristics of the EH Antenna make it the antenna of choice.
An additional advantage of the EH Antenna is that it provides signal power equal to that of a conventional tower while requiring only half the conventional tower’s height. This website includes a document entitled “El Salvador,” which reports on the installation and test of the first 700 KHz EH Antenna. Many more EH Antennas will follow.
A process has been initiated that will allow the FCC to grant broadcasters a license to use the EH Antenna in the United States. Current regulations require AM broadcast antenna vertical radiation patterns to conform to a specific equation that was originally devised for a conventional tower with radials. The EH Antenna is especially well suited for night-time operation because it requires a smaller vertical radiation pattern.

The EH Antenna boasts several features which make it the antenna of choice for most broadcasting needs. First is its small size and its ability to be mounted on a tower about half the height of a standard broadcast tower. The EH Antenna is also a complete dipole antenna and requires no ground radials other than a lightning ground connected to the tower. The EH Antenna also features very high efficiency and a wide bandwidth.
Compare these characteristics to those of a conventional antenna which requires a greater tower height, several acres of ground for its 120 buried ground radials, and a complex matching network and is less efficient than the EH Antenna. The documents provided in this website explain these differences in greater detail, but even without reading them you can see that the unique features of the EH Antenna translate to a better system at a lower cost than the traditional antenna.
Obviously, economics dictate the use of an EH Antenna unless the cost of land is insignificant. However, another major factor in favor of the EH Antenna is its reliability. The antenna has two cylinders, a tuning coil, and a single capacitor. A high quality capacitor has virtually infinite life, as do the other parts of the EH antenna. Compare that to a standard tower that requires a complex matching network that uses numerous components, any of which could become faulty at any time, adversely affecting broadcast quality.
The prototype AM broadcast EH Antenna was located in Eatonton, Georgia, and tested in accordance with conventional FCC procedures in 2003 by Stu Graham, a broadcast consultant. For convenience it was located at a low height (one-tenth wavelength), yet it offered great performance.
As with all prototype systems, its purpose was to identify any issues before beginning production. The only issue was that the instantaneous bandwidth was much lower than expected. Later it was discovered that the lowered bandwidth was caused by magnetic coupling of the cylinders to the steel tower sections inside which were used as supports. This reduced efficiency. However, the measured performance showed the antenna radiation was only 0.84 dB (18%) below a standard quarter-wave tower with 120 buried radials. The tower sections are now made of aluminum, and this problem no longer exists.
In 2007 a radio station in El Salvador, Central America, went on the air using an EH Antenna on 700 KHz. This station has excellent coverage of the country even though the height of the antenna is only 0.14 wavelengths, or 200 feet. A detailed performance report is included in this section of the website.
The El Salvador antenna is a “large” EH Antenna with a diameter of three feet and a total length of thirty-nine feet. The antenna can operate on any frequency between 540 and 1200 Hz with a simple change of its tuning coil. The antenna is rated at 10,000 watts. For radio stations running 1000 watts or less and on any frequency between 1200 and 1700 KHz, a smaller antenna is available. It is designed to sit on top of either a guyed or unguyed tower, uses cylinders that are eight inches in diameter, and has a total height of less than twelve feet.
When mounted on a standard 100-foot-tall self-supporting tower, this antenna will provide coverage equal to or greater than a conventional quarter-wavelength broadcast tower with 120 buried radials. In contrast, the conventional tower would be 205 feet tall at 1200 KHz.

Because of the EH Antenna’s small size, it is now possible for the first time to locate a radio station in a densely populated area. The EH Antenna can even be mounted atop a large building because it does not require ground radials. Because the smaller EH Antenna has much greater bandwidth than a conventional tower, the fidelity of the broadcast audio is limited only by the transmitter, not the antenna.
For detailed performance data on the prototype antenna, please contact Graham Brock, Inc. at As stated earlier, a full report on the radio station in El Salvador is included on this website.

Welcome to the Amateur Radio section of the EH Antenna website. The EH Antenna has useful applications in all areas of communications and offers many advantages to ham radio operators. It is a very small yet very high performance antenna. Its smaller size increases communications opportunities for many hams who have been restricted by a lack of space to grow antennas. How can an antenna be so small and have such high performance? The answer is that the EH Antenna is a new concept in antenna theory, and therefore does not need to follow the rules of older antenna theory.
The Hertz antenna has been around since the 1880s, and today there are an unlimited number of variations on that early concept. However, each variation is limited within the constraints of a resonant antenna. The wires may be straight or bent into various shapes, but they must be resonant, or resonated with an antenna tuner. Resonance is necessary for maximum current flow. Hertz antennas are based on the concept that current flow on a wire causes the development of a magnetic (H) field and that a changing magnetic field creates an electric (E) field. Because one field creates the other, they have a time phase difference of 90 degrees. The two fields do not become in phase and develop radiation until they have traveled a distance of about one-third of a wavelength from the wire. This is called the “far field.” When the fields have the proper phase, amplitude, and physical relationship, radiation is created.
Compare the older antennas to the EH Antenna, where the E and H fields are actually in time phase at the antenna itself. Because the two fields are very efficiently integrated, the radiation resistance is higher than that of a wire antenna. A major factor is that the elements of an EH Antenna are cylinders and have a much larger diameter than a wire. The two elements, therefore, have high capacity between the elements, which, in turn, allows the antenna to be small. This large capacity and high radiation resistance combine to provide very wide bandwidth and high efficiency. All of this comes from an antenna that may be less than 1% of a wav elength, compared to wire antennas that are 50% of a wav elength, or ¼ wav elength with radials. On this website you will find technical information that will allow you to roll your own. We hope you enjoy this information and the use of the antennas you build. There are an untold number of EH Antennas already on the air, and many more are added every day. If you choose to buy rather than build, we have provided a link to the only company that currently manufactures and sells the EH Antennas under a license agreement.
For those hams without antenna and RF experience, buying is most likely the better option. However, we have also provided some helpful hints to those hams who feel competent enough to build their own antennas or who enjoy a challenge. First, choose a diameter that is equal to or greater than those indicated in the list below. “Meters” refers to the Ham band.
80 meters: 4 inches
40 meters: 2 inches
20 meters: 1.5 inches
10 meters: 1 inch
You may use a smaller or larger diameter to achieve less or greater bandwidth, respectively. Make each of the two cylinders equal to six times the diameter, and space the cylinders the same as the diameter. This is relatively easy, but it gets harder from here. The next step is to wind a tuning coil and locate it about three diameters below the lower cylinder. This coil resonates the capacity of the cylinders. Like a Hertz antenna it is resonant. However the difference is that the antenna is a miniature dipole that is voltage fed, which allows the E and H fields to develop simultaneously. For the first try, use small wire with an enamel coating. Later you should replace it with heavier #14-gauge wire. Connect the top of the coil to the bottom of the top cylinder, and connect the bottom of the coil to the top of the bottom cylinder. Use a grid dip meter to find the resonant frequency, and then change the coil to bring it near the desired frequency. Next, connect a capacitor having a reactance of about 100 to 200 ohms to a tap on the coil about one-tenth the number of total turns above the bottom of the coil. Then connect a short piece of coax (less than five feet) to the antenna, connecting the shield to the bottom of the coil and the center conductor to the capacitor. Also connect a ground wire to the low side of the coil and to a good ground such as the power outlet safety ground in the shack.
Now it really gets interesting, so be sure you have the proper test equipment. You must adjust the tap on the coil to provide a 50-ohm match and adjust the coil by changing the top wires on the coil to bring the antenna close to the desired frequency. The desired frequency is best found by using a field strength meter and low transmitter power. It is preferable to use a signal generator for this test. A good impedance match is readily found by use of a VSWR bridge. Once this is accomplished, you must mount the antenna to simulate the final location. Connect a wire from the bottom of the coil to ground. This stabilizes the capacity of the antenna and allows final tuning and matching.
When the antenna is mounted vertically, it is a great general-coverage rag chew antenna on the low bands and a great DX antenna if the height is between one-eighth and three-eighth wavelengths above the ground. The antenna is a miniature dipole and can be mounted horizontally for high-angle radiation on the low bands.
There is a great discussion forum on Yahoo ( if you need help in building or tuning your antenna.
Click here for a list of EH antennas available for amateur use. They are manufactured by FR Radio Lab in Japan, the only manufacturer that is currently licensed to manufacture EH Antennas for ham radio operators.

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