# Whose Right and Whose Left--CP

• Subject: [amsat-bb] Whose Right and Whose Left--CP
• From: "Ben" <b-fisher@xxxxxxxx>
• Date: Thu, 31 Oct 2002 12:35:23 -0600

```Hello
The only definition of RHCP and LHCP that I have heard that makes sense
appears to be wrong. Let me explain the way that makes sense to me. Long ago
in college I learned the right hand rule for electric current vs magnetic
flex lines. It is based on the Cartesian Coordinate System that all of us
that have had high school geometry should understand. In other words if one
were to take their right hand with thumb extended and fingers curled. Than
define the direction of wave propagation as being from the base of their
hand to the tip of their thumb. Their fingers are now pointing in the
direction of positive field rotation. With this definition in mind, pretend
you are behind an antenna. Now point your right hand thumb at your face. If
you follow the curvature of your fingers than a wave front that is traveling
to you from a right handed transmitter will be rotating CCW from your
prospective. Turn your hand around so that your thumb is now pointing up the
boom in the direction a wave front would be moving if you were to transmit
from a RHCP antenna. From your prospective the wave front would be rotating
CW as it travels out into space. Think of it in another way. To screw a
right handed screw into a piece of wood you would need to turn it clockwise.
Your the transmitter. To retrieve the screw you would have to turn it CCW,
your the receiver. With a left hand screw CCW to embed the screw and CW to
retrieve it. This is all clear to me, but it is in direct contrast to how
AMSAT defines polarization. AMSAT's definition seems incomplete. All that is
stated is that if one stands behind an antenna and RECEIVES a signal that is
rotating clockwise than it is RHCP. But its not. Amsat's definition holds
water only if you make the definition that your thumb points in the
direction that the wave is coming from. I wish they would make this
distinction clear in there literature. There would be a whole lot less
confusion.
Sorry for the long post
Ben K9BF

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