[TowerTalk] Inverted L longer than 1/4 wave.

[Steve Hunt]

John,

No, an inverted L doesn't need to be resonant.
Increasing the total length raises the radiation resistance, and that 
may help the efficiency if you have a "less than perfect" ground system.
However, assuming that increasing the total length means increasing the 
length of the horizontal top, that puts more current into the horizontal 
section which in turn gives you much less low-angle radiation.

Here's some modelled figures - all with a 50ft vertical section, and 
over a reasonable ground system:

1/4 wave: Z=19+j0  Wave angle=30degrees
3/8 wave: Z=63+j690 Wave angle=84 degrees
5/8 wave: Z=80-j500 Wave angle=88 degrees

Hope that helps,

Steve G3TXQ

John King wrote:
> According to Editors and Engineers Handbook, the inverted L is a form of Marconi antenna. It further says that it is usually 1/4 wavelength long which is approximately 137 to 138 feet long for 160 meters.
>
> Does an inverted L antenna have to be resonant?
>
> What would be the result if you had room to make the inverted L 5/8 wavelength long? Would that make the feed point impedance higher and easier to feed. Also would the antenna have better radiating characteristics? Maybe give it a little gain? I have the room to extend an inverted L in that manner.
>
> I am in an antenna project re-erecting towers, and loops as well an HF quad. I am still in the planning stage for the lower frequency HF antennas. If you have experience with longer inverted L antennas or have experimented with them, I would appreciate knowing the benefit of your hands on experience. Thanks and 73, John, K5PGW
>
>
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