[amsat-bb] Re: More: circular polarization (1/4wave physical distance)
hamoen at iae.nl
Sat Sep 20 08:03:31 PDT 2008
Maybe my question becomes clearer with thse pictures (taken today)
1. this morning, the original set-up, on the roof
2. this afternoon, stripped, waiting for advice from the amsat-bb :-)
> 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
> - switch box for H/V/LHCP/RHCP in the shack (2 long cables needed)
> 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:
> 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
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