A helically-wound dipole or monopole that is physically short in terms
of a free-space wavelength can be made electrically resonant at its
input terminals as a result of the inductance of the helical form of
the radiating conductor.

But that does not mean that it has all of the electrical
characteristics of a linear conductor that is inherently resonant,
without the need for inductive loading.

The radiation resistance of such a helically-wound radiator can be
much lower than a naturally resonant radiator, which can mean that the
percentage of transmitter power radiated by the antenna SYSTEM can be
much lower than when a naturally resonant radiator is used.

The link below leads to a page developing this point from Kraus'
Antennas For All Applications, 3rd Edition.

http://i62.photobucket.com/albums/h8...ndVertical.gif

RF