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MFJ ANTENNA-TALK #7
1/2 Wavelength "L" Antenna
The ½ wave Inverted "L" antenna, with Hi-Z feed point requires only a minimum ground to be an effective radiator. Accommodate coax lines with an L-Network match.
Use the formula: 492/fMHz (259.4 @ 1.9MHz for example) to find the overall length of the aerial, which is composed of H (Horizontal) + V (Vertical) components. Try to get the vertical section as tall as possible, since the current distribution is maximum at the midpoint of the aerial (129.7 Ft @ 1.9 MHz). That being true, it can provide good radiation from both H and V components. The H component can slope down (or up), but this tends to skew the max radiation towards the direction of slope, which is sometimes desirable. For instance: working VK/ZL, JA, Africa, or Europe.
The overall best advantage of the aerial is that only a minimum ground is needed unlike the 1/4 wave version. Make for 160, 80, 40, or 20 meters with the appropriate single-band L-network. Patterns vary per band if actually cut for 160, then used also on 40 or 80. 40 is good off the ends; 80 is good broadsides and vertical at the same time (more so than on 160). Use a tunable L-Network or any antenna tuner capable of matching high impedance loads, and it's a good multiband system. Discrete parts (wire, insulators, pre-cut coils, and capacitors) are available from MFJ.
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