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: [email protected] [mailto:[email protected]] 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 [email protected] wrote:
From: John B. Stephensen [email protected] Subject: Re: [amsat-bb] RH and LH CP simutaniously To: "R. Chastain" [email protected], "Amsat-BB" [email protected] 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" [email protected] To: "Amsat-BB" [email protected] 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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_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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