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Re: Re: Is hardwire RHCP OK?



On Mon, 19 Oct 1998, Bob Bruninga wrote:

> On Sun, 18 Oct 1998, Richard W L Limebear wrote:
> 
> > > need to ever switch to left hand cp?  If I encounter trouble with cp 
> > > switching could I just wire it in RHCP and I if  so what would I miss?  
> > 
> > I hardly ever use LHCP but its there if I want it. You wouldn't miss much.
> 
> Since I got my new Kenwood prototype dual band HT with built in 9600 baud
> TNC, I have spend many passes outside with a handheld 3 element beam
> copying passes of the 9600 baud satellites.  I can say, that
> I have never seen any detectible circularity on the downlink. 

I believe that the UoSAT birds and AO-27 have linear-polarized downlinks.
As Bob noted, a circularly-polarized antenna can help alleviate fading as
the polarization observerd by the ground station chages over a pass, but
there is no inherent circular polarization in the signal.  

The Pacsats have either RHCP or LHCP downlinks, so polarization switching
on the ground can be of great help (WD0E has oted this as well over the
years).  

Most of the LEO birds seem to have linear polarized receive antennas, so a
circular polarized uplink of either sense should, at least in theory,
provide resistance to fading. 

Real-world experience, of course, may deviate quite a bit from theory
(e.g., if it works, use it....)

73, Steve  KA1LM@amsat.org

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