In a 1/4 wave inverted L the horizontal part carries little current so it does serve mostly to add capacitance.

A 3/4 wave inverted L is different. It delivers omnidirectional vertically polarized radiation from the vertical portion and dipole-like horizontally polarized radiation from its horizontal portion. On 40M a common arrangement is about 33' up and 67' across, though the 2:1 radio is not important, rather it's the length for resonance.

For more info see my QST article in the July 1991 issue. "A Simple Effective Dual-Band Inverted L Antenna." It was also included in the ARRL Handbook for 2000 and other years.

Dennis Monticelli AE6C