Thursday, February 17, 2011

The 1.8-MHz inverted L.


Overall wire length is 165 to 175 ft. The variable capacitor has a maximum capacitance of 500 to 800 pF.


The antenna shown in Fig is simple and easy to construct. It is a good antenna for the beginner or the experienced1.8 MHz DXer. Because the overall electrical length is greater than 1/4 ë, the feedpoint resistance is on the order of 50 Ù, with an inductive reactance. That reactance is canceled by a series capacitor, which for power levels up to the legal limit can be a air-variable capacitor with a voltage rating of 1500 V. Adjust antenna length and variable capacitor for lowest SWR. A yardarm or a length of line attached to a tower can be used to support the vertical section of the antenna. (Keep the inverted L as far from the tower as is practical. Certain combinations of tower height and Yagi top loading can interact severely with the Inverted-L antenna—a 70-ft tower and a 5-element Yagi, for example.) For best results the vertical section should be as long as possible. A good ground system is necessary for good results.

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