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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