Simple helix


    Images 1
    Images 2


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Helix antenna design and construction details

Antena helicoidal When we received a parabolic reflector 'on loan' from a local cellphone company, some thinking was in order. We were planning several other antennas of this type for weather satellite tracking, so some time to gather information was needed.

As a helix is easy to construct, and very tolerant of size errors, it's an excellent plaything.

According to literature, the minimum number of turns for a helix is between 3 and 5. Only after 3 turns, acceptable circularity is realized. Still, with the f/d ratio of the available reflector, we needed near 3 turns to illuminate it efficiently. So maybe this solution is a bit of a compromise.

Here's a page with images of a 3-turn helix that was constructed for reception in the 1690 MHz Wefax band (geostationary weather satelliteslike GOES).
These images are not photographs but generated with a raytracing programa (POV-Ray).

Documentation and links

Helical Antenna Design
  Bob Atkins KA1GT, The ARRL UHF/Microwave Experimenter's Handbook,
ISBN 0-87259-312-6 (More info at Amazon.com)

Die Helical-Antenne
  Karl Rothammel Y21BK, Antennenbuch, Telekosmos Verlag, ISBN 3-440-04791-1

How to Make a Simple 2.425GHz Helical
  Jason Hecker, http://www.air.net.au/~jason/heliaerials.html


(c) John Coppens ON6JC/LW3HAZ mail