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The HF radio spectrum is generally considered to be 2-30 MHz. In this frequency range antennas need to be physically large to enable good coupling to "space" and hence efficient radiation. As an example, at 5 MHz a half wave dipole is around 30m in length and 2 MHz it is 75m long. Half wave dipoles are very efficient radiators but they are narrow band (only work over a very small frequency range) before serious impedance mismatch occurs. This mismatch can be accommodated using an antenna tuner but these add to costs and modern HF communication often uses frequency hopping techniques. Even automatic antenna tuners will not work with frequency hopping signals. Broadband HF base antennas traditionally fall into two main categories, resistively loaded antennas which can be inexpensive and reasonably compact but inefficient, or large elaborate and very expensive, non-loaded designs. (These can cost upward of $80,000 to purchase and install). The challenge for many years has been to devise an antenna which is an efficient radiator, compact, and also inexpensive. Previous solutions include the Barker Williamson folded dipole, the Australian traveling wave dipole and other designs by Guertler etc. Many "broadband" designs have also been offered by the Amateur Radio community but these are generally not true broadband antennas as they only work well (without an antenna tuner) in the harmonically related Amateur bands. A true HF broadband antenna will work continuously across most of, if not all of the HF spectrum with good radiation efficiency and minimal compromise of the radiation pattern. The Robinson Barnes HF Broadband Antenna was conceptualised and developed in the early 1990s by Graham Robinson and John Barnes and has become a widely used design for commercial and military HF base stations, where ground space is limited, yet a full 4 octave bandwidth (2-30 MHz)is required. It is a centre fed wire antenna with two arms each consisting of 3 radiating elements and is generally tower mounted, either horizontally or as an "inverted V" The design has almost double the radiation efficiency of the HF folded dipole of the same length and is nearly half the size of other traditional HF wire antennas such as the "Australian travelling wave dipole" The standard size Robinson Barnes antenna is only 27m in length. Various Models are available in lengths of 20, 27, 54 & 74 Metres and power ratings of 125w to 1kW Continous - Ruggedized versions are also available for extreme environments Graham Robinson was the founder of (Bushcomm HF Antennas ) located in Perth Western Australia. The "RB" Travelling Wave Antenna is popular for use by Governments, UN, Military, NGOs,and is marketed in various configurations as a (BBA-100 ). ==References== 〔 * Antennas. J.D. Kraus McGraw-Hill * Electronic Radio and Engineering. F.R. Terman. MacGraw-Hill * Terrestrial Radio Waves. Dr.H. Bremer. Elsevier Publishing Co. * Ultra & Extreme Short Wave Reception. M. Strutt. Van Nostrand 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Robinson Barnes HF Broadband Antenna」の詳細全文を読む スポンサード リンク
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