INTRODUCTION TO AM BROADCAST
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 www.grahambrock.com. As stated earlier, a full report on the radio station in El Salvador is included on this website.