On Sun, 13 May 2012 20:13:40 +0200, Bob- W7LRD w7lrd@comcast.net wrote:

Agreed... occasionally, sometimes left, right, vertical or horiz will be best. Then is that for the up or downlink ? Essentially I have discovered it is a crap shoot. Whatever works at any given moment may not work (that well) a few minutes later. I believe Domenico had a scheme for switching any of the four. These uncertainty's make it fun.

still rebuilding all antennas

73 Bob W7LRD

Seattle

----- Original Message -----

From: " Ib Christoffersen " <oz1my@ privat . dk > To: "David 4X1DG" <4x1dg@ iarc .org>, amsat -bb@ amsat .org Sent: Sunday, May 13, 2012 10:44:55 AM Subject: [ amsat -bb] Re: Circular polarization

Hi David, The short answer is NO.

But there are more to it than that :-)

I think I still have an article about that if you are interested.

73 OZ1MY/ Ib

----- Oprindelig meddelelse ----- Fra : amsat -bb-bounces@ amsat .org [ mailto : amsat -bb-bounces@ amsat .org] På vegne af David 4X1DG Sendt : 13 May 2012 18:31 Til: amsat -bb@ amsat .org Emne : [ amsat -bb] Circular polarization

Is a UHF circular polarization antenna needed for the current operational satellites? I am planning some work on my antenna system and wonder if the CP is needed, or actually, deteriorate the signal by 3dB if the satellites are using linear antennae??

The best option would probably be a rotatable antenna, a sat will never be fully horizontal vertical or circular, sometimes it even makes a difference when you flip 180 degrees.

---- Original Message ----- From: "David 4X1DG" 4x1dg@iarc.org To: amsat-bb@amsat.org Sent: Sunday, May 13, 2012 6:30 PM Subject: [amsat-bb] Circular polarization

...

Is a UHF circular polarization antenna needed for the current operational satellites? I am planning some work on my antenna system and wonder if the CP is needed, or actually, deteriorate the signal by 3dB if the satellites are using linear antennae??

The best option would probably be a rotatable antenna, a sat will never be fully horizontal vertical or circular, sometimes it even makes a difference when you flip 180 degrees.

-- 73 Andre PE1RDW

Hi Andre, PE1RDW

I agree.

A rotatable boom by 90 degrees is a very good option for a linear antenna because in a certain moment a sat can send to you a polarization between linear or through circular i.e. an elliptical polarization that can be matched by turning the antenna over the boom.

BTW since the polarization changes very rapidly the speed of rotation of the boom must be very fast, let say maximum 10 seconds or less to rotate from 0° to 90°

73" de

i8CVS Domenico

http://www.pa3guo.com/cushcraft_416tb.html

-----Mensaje original----- De: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] En nombre de i8cvs Enviado el: domingo, 13 de mayo de 2012 20:44 Para: Bob- W7LRD; Ib Christoffersen CC: Amsat - BBs; David 4X1DG Asunto: [amsat-bb] Re: Circular polarization

----- Original Message ----- From: "David 4X1DG" 4x1dg@iarc.org To: amsat-bb@amsat.org Sent: Sunday, May 13, 2012 6:30 PM Subject: [amsat-bb] Circular polarization

Is a UHF circular polarization antenna needed for the current operational satellites? I am planning some work on my antenna system and wonder if the CP is needed, or actually, deteriorate the signal by 3dB if the satellites are using linear antennae??

----- Original Message ----- From: "Bob- W7LRD" w7lrd@comcast.net To: "Ib Christoffersen" oz1my@privat.dk Cc: amsat-bb@amsat.org; "David 4X1DG" 4x1dg@iarc.org Sent: Sunday, May 13, 2012 8:13 PM Subject: [amsat-bb] Re: Circular polarization

<snip>

I believe Domenico had a scheme for switching any of the four. These uncertainty's make it fun.

still rebuilding all antennas

73 Bob W7LRD

Seattle

Hi Bob, W7LRD

My articles "SWITCHING FOUR POLARIZATION ON A 70 cm CROSSED YAGI" was published in AMSAT-Journal March/April 2007 Part-1 and May/June 2007 Part-2

I can send both articles in pdf files to anyone is interested on it.

73" de i8CVS Domenico _______________________________________________ Sent via AMSAT-BB@amsat.org. 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

That has been my assessment and experience, too. Signals are consistent and there isn't any fiddling or switching polarization to worry about although I do find different results in signal strength between RHCP and LHCP on the same satellite sometimes.

73, Jerry N0JY

On 5/13/2012 3:59 PM, Trevor . wrote:

I've found circular gives consistantly better results than a linear polarized antenna with the current amateur satellites.

The IARU-R1 VHF Managers Handbook mentions standards for polarization on page 122. It can be downloaded at http://www.iaru-r1.org/index.php?option=com_remository&Itemid=173&fu...

73 Trevor M5AKA

--- On Sun, 13/5/12, David 4X1DG4x1dg@iarc.org wrote:

...

Is a UHF circular polarization antenna needed for the current operational satellites? I am planning some work on my antenna system and wonder if the CP is needed, or actually, deteriorate the signal by 3dB if the satellites are using linear antennae??

---

Sent via AMSAT-BB@amsat.org. 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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