Inverted-L antenna
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The inverted L is, as the name suggests an "upside-down" L.
Notes:
- The total length AC of the wire radiates in this antenna
- A good quality ground is required
- The vertical length AB should be as long as possible for best results
Theory of Operation
End-fed longwire antennas that are 5, 7, 9, 11, 13 or 15 electrical quarter-waves long will exhibit a feedpoint impedance of between 150 ohms and 250ohms. Using a 4:1 balun at the feedpoint will enable us to feed these antennas with a 50 ohm source and cable (usually coaxial cable).
Because the amateur bands are related harmonically it is possible to produce an inverted L antenna that is resonant or almost resonant on a number of bands.
For example:
- - a wire length of 128' (39m) will be resonant on 15m, 12m and 10m
- - a wire length of 121' (37m) will be resonant on 30m, 20m and 17m