[amsat-bb] More: circular polarization (45deg physical distance)
hamoen at iae.nl
Sat Sep 20 07:48:09 PDT 2008
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 :-)
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