Radiation Resistance: Short Verticals
Here's a chart out of Moxon's book, antennas for all locations:
Note: the chart is for dipoles; for verticals the Rr is half the amount shown.
So for a vertical 50% of full length:
- Capacitive end-loaded: 18 Ohms
- Inductive center loaded: 5 Ohms
As we know, efficiency depends on the ratio of Radiation Resistance to Ground Resistance. (OK, plus a tiny bit of d.c. resistance – which is negligible)
Thus, it is apparent that capacitive end-load (top-loading) is much more efficient than inductive loading, irrespectable of whether the loading coil is at the base or in the middle of the vertical.