[amsat-bb] Helix Antenna's Twist

Spectrum International, Inc spectrum.ma.ultranet at rcn.com
Sun Oct 24 04:03:03 PDT 2010

                                                       23rd October 2010
                N8MH de S.I.,

                     Your recent message to Tom, K0TW, in respect to the 
polarization of a helical antennae is not 100% correct.
You state, quote:
 "How do you determine the resulting polarity of the [helical] antenna?
    My response:  when standing at the rear, does the cork-screw go
clockwise or counter-clockwise as it spirals away from you?  That is
the visible difference, if building a helix. "

             Implicit in your answer (but not defined) is that a 
Right-hand helix, when viewed from behind, spirals away from you in a 
clockwise direction, the same as a standard screw thread.

             That statement is true for the classical helical antenna, 
/á la Kraus/.

            However it is not true for the Quadrifilar Helix design, 
which twists in the opposite direction to the classical helix.

            Maybe people who do not know the difference, and unwittingly 
build one with the twist in the wrong direction, get such very bad 
performance when attempting to use it and complain bitterly that "the 
Quad Helix does not work".

                            73s,    de  John  G3BVU/W1,
                                            Spectrum  International, Inc.

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