Re: [amsat-bb] Whose Right and Whose Left--CP REPLY

["Ben" <b-fisher@xxxxxxxx>]

Thanks Gunther and others
  The responses I received from my post seem to support my understanding of
CP. The cause of my confused state is a picture found somewhere on the net
that shows a man holding up a crossed yagi. In the picture the horizontal
yagi is closest to him and the vertical one is 1/4 wave length ahead or in
front of the horizontal one. The antennas are feed in phase. The high side
of the horizontal antenna is to the right of the boom and the high side of
the vertical antenna is above the boom. If a CP signal with the same CP as
the antenna is being received, it first hits the forward yagi than rotates
CW 90 degrees and intersects the second yagi. If one were to transmit from
the same antenna the signal would be rotating CCW from the perspective of
one standing behind the antenna. This is LHCP, but is stated to be RHCP. An
explanation has been given as to way it is RHCP. It states that as a signal
is being received it first hits the vertical Yagi and than rotated CW 90
degrees and intersects the horizontal yagi. It is stated that since this is
a CW rotation it is RHCP. This is in conflict with my understanding. An
incoming RHCP signal would be rotating CCW as it progresses through the
antenna and an out going signal would be rotating CW. This is indeed easy to
visualize when thinking in terms of a Helical antenna. I know that crossed
yagis are more difficult to understand. Can someone explain in more detail
way the crossed yagi is consider RHCP or is it defined wrong?

Thanks
Ben K9BF
----- Original Message -----
From: "Gunther Meisse" <gjmouse@neo.rr.com>
To: <amsat-bb@amsat.org>
Cc: "'Ben'" <b-fisher@uiuc.edu>
Sent: Thursday, October 31, 2002 2:12 PM
Subject: RE: [amsat-bb] Whose Right and Whose Left--CP REPLY


> Well, Ben. At the end you had it right (correct) No pun intended.... To
use
> the "Right Hand Rule" you must always point the thumb at the other end of
> the equation. When transmitting, point at the sky. When receiving from the
> bird, again, point the thumb at the sky, or with other words, point it at
> the transmitting or receiving source. With this rule you are indicating
the
> proper rotation ONLY. Do not try to be a wave front. You are making it to
> complicated.
> 73
> Gunther Meisse
> W8GSM
> PS This is great.... I remember so well in about 1960-65 we beat this
issue
> to death when the space program was starting to consider such things in
> antenna design...
>
> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
> Behalf Of Ben
> Sent: Thursday, October 31, 2002 1:35 PM
> To: AMSAT-BB
> Subject: [amsat-bb] Whose Right and Whose Left--CP
>
>
> 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
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org