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| Using A Tunable Buried Counterpoise System With A 160 Meter Horizontal Loop At NVIS By N0KHQ - St. Louis Hi All, I have been asked many times to explain how to adapt a Tunable Buried Counterpoise System to a Horizontal Loop (NVIS). I hope that the attached drawing explains what materials are needed and how to install the system. This design is for 160 meters. NOTE: This system is not to be confused with safety grounding. Do not ground the RF counterpoise system to any safety grounds. It must be installed exactly as shown. The System is a low loss return path for antenna currents. Since the counterpoise wire is buried, a measured wavelength (in the ground) is 40% shorter than a wavelength in the air.. As you may see from the drawing below, it becomes very clear how the system works. It works as a complete circuit. To test the system for effectiveness, after installation, tune up the antenna with the antenna tuner, then tune up the Ten-Tec 1251, (from Ten-Tec purchase a 1251 RF Counterpoise Tuner, it comes in kit form and will require assembly), for maximum current reading on the meter. While talking to a distant station ask them to note your signal strength and loudness of your audio, then purposely de-tune the TT-1251 for a minimum current reading on the meter. The distant station will notice a drop in your transmitted signal and a reduction of audio loudness. Many tests have been run on this system and all I can say is “IT WORKS!” As you are aware a transmitting antenna is coupled to the earth unless it is one wavelength above ground. When the antenna is less than a wavelength, the antenna is coupled to the ground and about 40% of the transmitted current is going into the ground to heat it up. The counterpoise collects these antenna currents and returns them back to the source (the antenna tuner) to be re-radiated back into the antenna. (It’s a closed circuit) thus adding 3db to 6db of gain to the already existing antenna gain. Hope all of you are doing well. Spring is almost here…..you know what that means…..its time to plant some new antenna designs. Make sure you use plenty of rf fertilizer! Editors Note: Ten-Tec......Made in Tennessee.....U.S.A! Take Care 73! John / N0KHQ / St. Louis Email: N0KHQ@Aol.Com |
| NOTE: Bury as much of the coax from Counterpoise tuner as possible to reduce any pickup of man made or atmospheric noise. |
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