Thanks to Domenico for sharing the work done by K4KJ. It is amazing how much good information there is out there. It takes a bit of digging to find it but it is worth the effort. The configuration shown in figure 14 looks promising but probably too difficult to put on a sat.
W9KE Tom Doyle On Sat, Aug 4, 2012 at 10:18 PM, i8cvs <[email protected]> wrote: > Hi All, > > I agree completely with Bob, WB4APR and this is what is wery well > explained into the article "CIRCULAR POLARIZATION by K4KJ, > a zipped file 5 MB long available from me. > > 73" de > > i8CVS Domenico > > ----- Original Message ----- > From: "Bob Bruninga " <[email protected]> > To: "Thomas Doyle" <[email protected]> > Cc: <[email protected]>; "andrew abken" <[email protected]> > Sent: Sunday, August 05, 2012 12:24 AM > Subject: [amsat-bb] Re: Antenna Polarization Technical Question > > >> > Not sure why anyone would want to maintain the >> > orientation of the satellite in such a way that >> > would cause the direction of circular >> > polarization to change during the path. >> >> Lets try this approach... As I said before, By the laws of physics, what > comes out one side of a circular polarized low gain antenna as RHCP comes > out the opposite side as LHCP. >> >> Now given that, and the fact that someone in Maryland is in the center of > the RHCP beam, then by the laws of physics, the guy in California must see > mostly LHCP. No matter how much one of those persons demands that he > deserves the RHCP beam, by definition, someone else somewhere will get the > LHCP one, and the geometry changes at least every 10 minutes or so and every > time the spacecraft rotates a bit. >> >> So one might say, "point it down" then only the person in Kansas will see > the main beam and those in CA or MD will be completely off the sides almost > 70 degrees from the main beam. Mot people do not realize how LOW these > satellites are. The only solution is to put satellites so high, that "down" > is about the same to everyone (geostationary altitude). But then that takes > 100 times more altitude, and that takes 10,000 times more power. >> >> Better to just live with the laws of physics... I guess. >> >> Bob, WB4aPR >> >> > >> >On Sat, Aug 4, 2012 at 2:47 PM, Bob Bruninga <[email protected]> wrote: >> >>> I believe that is true but that does not explain >> >>> why the optimum polarity setting on the receive >> >>> end would change during a pass. >> >> >> >> That's easy. The circularity on a pair of crossed dipoles (about all > you can get on a spacecraft) May be designed for Right hand circularity when > viewed from the prime direction. But by definition, that save waveform will > be LHC when viewed from the opposite direction. >> >> >> >> And since the geometry to any one observer is constantly changing by > almost 180 degrees during an overhead pass, that is why it is very easy to > see, complete change in circularity. >> >> >> >> Bob, WB4APR >> >> >> > >> > >> > >> >-- >> > >> >Sent from my computer. >> > >> >tom ... >> _______________________________________________ >> Sent via [email protected]. Opinions expressed are those of the author. >> Not an AMSAT-NA member? Join now to support the amateur satellite program! >> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > -- Sent from my computer. tom ... _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
