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Re: Whose Right and Whose Left--CP REPLY



And this is why, in July 1962, the first Telstar transatlantic satellite TV
relay failed on the first pass in the UK as our dish feed at Goonhilly Down
had the wrong circular polarisation.

At least that was the story I was always told as a "boy". Certainly 90+ mins
later the picture was noise free.

I have visions of a white coated engineer being despatched up to the feed
point of a ?60 foot dish between passes having quickly made another feed up
out of bent coat hanger wire or similar......

Maybe someone here on the BB knows the truth!

It ran about 3 watts out on 4170MHz so the helix would have been pretty
small.


cheers

Graham G3VZV

----- Original Message -----
From: "Gunther Meisse" <gjmouse@neo.rr.com>
To: <amsat-bb@AMSAT.Org>
Cc: "'Ben'" <b-fisher@uiuc.edu>
Sent: 31 October 2002 20:12
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
>
> ----
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>
> ----
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