[amsat-bb] Re: RH and LH CP simutaniously

[Art McBride]

Hi All,
My thoughts: 
The polarization is a function of the pointing angle of the Space Craft
antenna. If you are looking at the back side the polarization will be
opposite rotation. Switching polarization will improve performance provided
the antenna does not have a large front to back ratio. Reflections also will
reverse the polarization but they are at least -15 db lower than the direct
signal. 
Switching from right to left hand rotation is something that is done if you
experience a fade and most of the time the change is not beneficial.
Continuous switching will give signal 1/2 the time and noise the other half
of the time. The net result is a 3 dB loss in signal all of the time as the
signal is never equal in both rotations at he same time for the same
observer location.

Art, KC6UQH

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of R. Chastain
Sent: Saturday, January 03, 2009 7:33 PM
To: Amsat-BB
Subject: [amsat-bb] Re: RH and LH CP simutaniously

But if the switching frequency was say.... 30-40khz, wouldn't the sidebands
be so far out of range so as not to cause interferance.
 
RoD
KD0XX

--- On Fri, 1/2/09, John B. Stephensen <kd6ozh at comcast.net> wrote:

From: John B. Stephensen <kd6ozh at comcast.net>
Subject: Re: [amsat-bb] RH and LH CP simutaniously
To: "R. Chastain" <suenrod at yahoo.com>, "Amsat-BB" <amsat-bb at amsat.org>
Date: Friday, January 2, 2009, 6:30 PM

You can use a 90-degree hybrid splitter/combiner to produce LHCP and RHCP
for
two receivers. Switching will produce sidebands at the switching frequency
and
alias undesired signals into the receiver passband.

73,

John
KD6OZH

----- Original Message ----- From: "R. Chastain"
<suenrod at yahoo.com>
To: "Amsat-BB" <amsat-bb at amsat.org>
Sent: Friday, January 02, 2009 23:15 UTC
Subject: [amsat-bb] RH and LH CP simutaniously


Hi all,
Has anyone ever considered the possibilty of using PIN diodes and a free
running square wave oscillator to electronically switch between RHCP and
LHCP?
The switching frequency would have to be high enough so as to not introduce
a tone to the signal.

Just a thought I have had for awhile.

RoD
KD0XX



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