[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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