[amsat-bb] Re: STRaND1 polarity shift observation
g.shirville at btinternet.com
Tue Mar 5 00:58:41 PST 2013
Well this is not "official" but I can advise that the antennas on Strand-1
are both single 1/4 wave monopoles. They project from near the corners of
the structure as indicated here
sorry for the long link!
I do not know whether the satellite attitude has yet been stabilised nor
whether the solar panels have been deployed but there is not much sign of
rapid signal strength changes during a pass.
Sent: Tuesday, March 05, 2013 12:02 AM
To: Ken Swaggart ; Amsat - BBs
Subject: [amsat-bb] Re: STRaND1 polarity shift observation
If STRaND1 has a circularly polarized crossed dipole antenna like that
depicted in Fig 12 of the article "The Advantages of Circular Polarization
for Amateur Satellite Ground Station " by K4KJ already in your hands
than it is easy to understand why STRaND1 was stronger when you
selected LHCP while approaching TCA and why after TCA, RHCP
was stronger while the satellite was receding.
Fig-12 shows that if two crossed dipoles are mounted over the same
plane and are supplied with 90 degrees out of phase than the polarizazion
is RHCP in one axial direction and LHCP in the opposite axial direction
and this can explain why the signal was stronger when you selected
LHCP while approaching TCA and why after TCA, RHCP was stronger
while the satellite was receding.
BTW unfortunately actually there are not official informations from
AMSAT-UK about the polarization of the STRaND1 70 cm antenna
and without this information it's very difficult to answere your question.
----- Original Message -----
From: "Ken Swaggart" <k.swaggart at charter.net>
To: "i8cvs" <domenico.i8cvs at tin.it>; "Amsat - BBs" <amsat-bb at amsat.org>
Sent: Monday, March 04, 2013 5:02 PM
Subject: Re: [amsat-bb] STRaND1 polarity shift observation
> Thanks for sending the K4KJ article.
> However my question was why does STRaND1, which only has a whip antenna,
> sometimes appear to exhibit circular polarity characteristics? I would
> expect a whip antenna transmitting from space to have the same signal
> strength on the ground using either RH or LH polarity on my receiving
> Ken, W7KKE
> -----Original Message-----
> From: i8cvs
> Sent: Monday, March 04, 2013 00:42
> To: Ken Swaggart ; Amsat - BBs
> Subject: Re: [amsat-bb] STRaND1 polarity shift observation
> Hi Ken, W7KKE
> The answere to your question is clearly described into the zipped article
> "Circular Polarization" by K4KJ, 5 MB long that I have sent to you in
> a separate email.
> 73" de
> i8CVS Domenico
> ----- Original Message -----
> From: "Ken Swaggart" <k.swaggart at charter.net>
> To: <amsat-bb at amsat.org>
> Sent: Monday, March 04, 2013 5:10 AM
> Subject: [amsat-bb] STRaND1 polarity shift observation
> > During my last pass at 0332Z, max elevation 45 degrees out over the
> > I noticed that STRaND1 was stronger when I selected LHCP while
> > TCA. After TCA, RHCP was stronger while it was receding. I believe
> > cubesat uses a whip, so not sure what is causing this.
> > Anyone have an idea why?
> > Tnx,
> > Ken, W7KKE
> > CN75xa
> > _______________________________________________
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