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The Three L-Antennas: Wide-Equal-Tall A half-wave dipole exhibits diferent radiation patterns when bent into space saving forms. Starting with the basic "L" form with arms of equal length, this article covers:
Modified Ground Plane Antenna Adds Second Band This article presents the concept of combining the characteristics of a conventional Ground Plane Antenna (GPA) with the elements of an Off-Center-Fed (OCF) antenna. Various configurations provide a simple way for multi-band performance and an unusual way to obtain relatively strong directional gain.. all from a very ordinary antenna. Antennas 101: The Basics by Ward Silver, N0AX Author/Editor of all the ARRL license manuals and most ARRL publications. Contributing Editor for QST "Hands-On-Radio" column and many articles. Bill Orr Technical Writing Award Recipient. This is an extremely concise, accurate and understandable antenna presentation by the ARRL master. The best! (This link takes you to the ARRL web site. Use the "Return" symbol to go back to Bent Dipoles). "End Effect" on an End-Fed-Half-Wave Antenna Feeding a half-wave antenna near an end gives the advantage of resonance on all harmonics for multi-band performance. However, there is a problem in the alignment of the first two harmonics. The reason for the problem is called "End-Effect". This article explains and quantifies the issue. Modeling the Firestik Antenna The Firestik is an American 27 MHz vertical ground plane antenna for the 11 Meter Citizens Band. There are no known NEC antenna models so this article reverse engineers what little information found on the internet to find the probable top-loading scheme used. Fom this three 4NEC2 models are created. The study results for 4 foot, 3 foot and 2 foot Firestiks are presented. All three anenna models are included. Sloop Rigged Utility Antenna Here is a compact, all-purpose, no radials, portable antenna for 6 through 20 meters. All it takes is a wooden pole and two 17 foot stainless steel telescoping antennas supported by sail rigging. Complete building instructions are given. The 2-Band Tri-pole Antenna A mono-band dipole can operate on a second band by adding a third element. The added element shortens the dipole 10 to 20%. This article discusses principles of operation, tuning, gain, radiation patterns and take-off angles. Instructions are given to build any Tri-pole antenna in the range of 6 to 15 meters. Half-Size 6 Meter J-Antenna A 6 Meter J-Antenna is around 14 feet tall. A little known characteristic of this famous antenna is used to reduce its length to 7 feet. Perfect 50 Ohm match. Same gain. No radials. Zeppelin Antenna as a HF 2-band Dipole Explained here is how this universally famous J-type antenna can be made with a tunable harmonic. This allows independant operation on unrelated frequencies on two harmonically related bands such as 10 and 20 meters. Bonus: the antenna is about 15% shorter than a 20 meter dipole. Dick Reid, KK4OBI at qsl.net |