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Re: More: circular polarization (1/4wavephysicaldistance)



Hi Henk, PA3GUO

Since the physical distance between elements of your 70 cm crossed yagi
is 1/4 wave over the boom I suggest you to read my article:
"Switching four Polarizations on a 70 cm Crossed Yagi" published by the
 AMSAT-Journal

Part-1 ( the theory ) issue of March/April 2007
Part-2 (construction) issue of May/June 2007

If you need the above articles I can send to you a pdf file of it.

73" de

i8CVS Domenico

----- Original Message -----
From: "Henk, PA3GUO" <hamoen@iae.nl>
To: <amsat-bb@amsat.org>; <""@iae.nl>
Cc: <pa3guo@amsat.org>
Sent: Saturday, September 20, 2008 5:03 PM
Subject: [amsat-bb] Re: More: circular polarization (1/4wave
physicaldistance)


> Maybe my question becomes clearer with thse pictures (taken today)
>
> 1. this morning, the original set-up, on the roof
>    http://www.pa3guo.com/416_original.jpg
>
> 2. this afternoon, stripped, waiting for advice from the amsat-bb :-)
>    http://www.pa3guo.com/416_stripped.jpg
>
> Henk
>
> > So !
> >
> > As the discussion is ongoing anyway:
> >
> > This is how I have done it for 2 meters:
> > - 2 x 6 elements (phyically same position, no 1/4wave distance
> >   http://www.pa3guo.com/dk7zb.html
> > - switch box for H/V/LHCP/RHCP in the shack (2 long cables needed)
> >   http://www.pa3guo.com/polarizer.html
> >
> > But now 70cm !
> > My 13 year old Cushcraft had always fixed circular polarization.
> > - 435.300 (AO51) had never any fading and was strong
> > - 435.150 (AO51) I could barely hear (proofs the >20 db separation)
> >
> > Now: as AO51 will be in an mode that I want to use in the coming
> > days, with the 435.150 downlink, I needed to change the polarization.
> >
> > Initially I wanted to have a temporal situation (swapping the
> > coax on the front dipol), but the screws needed replacement anyway, so I
decided to take the whole antenna down.
> >
> > The 2x8 elements beam has the 2 antennas mounted 1/4 wave distance
spaced on the boom (the physical method).
> >
> > Now, I want to be able to switch between LHCP and RHCP. Not fixed.
> >
> > A good website I found is:
> > http://sv1bsx.50webs.com/antenna-pol/polarization.html
> >
> > At the bottom the physical method for CP is described.
> > Almost what I needed, now I need to be able to switch on top of that.
> >
> > I would assume that this should still be possible :-)
> > My preference would be only LHCP and RCHP, no need for Hor or Ver.
> >
> > Prefer to have eg the coaxes of the 2 beams to a small relay box
> > on the back of the beam and then with a relais create the RHCP
> > vs LCHP.... but I lack the schematic for that :-)
> >
> > ... can someone point me to a URL that has the solution described ?
> >
> > OR: would it be simply this:
> > 1. take the front dipol
> > 2. swap conductor/shielding to create LHCP or RCHP AT the solder points
?
> >
> > (is this how WIMO is able to get it all in their small boxes)
> >
> > Well, I have 2 days before AO51 is in the mode I requested,
> > I really need to get the antenna in place :-)
> >
> > Thanks !
> >
> > Henk, PA3GUO
> > http://www.pa3guo.com
>
>
>
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