A helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. In most cases, helical antennas are mounted over a ground plane. Helical antennas can operate in one of two principal modes: normal (broadside) mode or axial (or end-fire) mode.
B: Central Support,
C: Coaxial Cable,
E: Spacers/Supports for the Helix,
R: Reflector/Base,
S: Helical Aerial Element
In the normal mode, the dimensions of the helix are small compared with the wavelength. The far field radiation pattern is similar to an electrically short dipole or monopole.
More information about this type of antenna:
http://www.educypedia.be/electronics/antennahelical.htm
http://www.vk2zay.net/calculators/?body=helical.php
http://en.wikipedia.org/wiki/Helical_antenna
http://helix.remco.tk/
http://www.dxzone.com/catalog/Antennas/Helical/
http://hastingswireless.homeip.net/index.php?page=antennas&type=helical
http://www.tuc.nrao.edu/~demerson/helixgain/helix.htm
http://www.rac.ca/tca/2005-11-Article%20by%20Clare%20Fowler.pdf
http://www.w6nbc.com/articles/QST1009QFH.pdf
p/s: i am thinking to make a helical antenna for 2m and 10m bands.
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