When a CP signal, bounces off a reflector, it reverses polarity. So if you are wanting to generate a RHCP pattern from a dish antenna, the feed needs to be LHCP so that it will come out RHCP after bouncing off the dish. Make sense?
73 ----- Jim Walls - K6CCC jim@k6ccc.org
-----Original Message----- From: "Greg D" ko6th.greg@gmail.com Sent: Wednesday, March 21, 2018 16:36 To: "Jean Marc Momple" jean.marc.momple@gmail.com, "Wendy and Terry Osborne" wandtosborne@gmail.com Cc: amsat-bb@amsat.org, "Burns Fisher" burns@fisher.cc Subject: Re: [amsat-bb] Antenna Polarization Question
Jean Marc Momple wrote:
In a nutshell/ my conclusion/ advice on the RHCP/LHCP issue: to operate the birds for HAM purpose the simplest way is just to have polarization relays on both uplink and downlink antennas, then manually switch polarization as required depending on the fading, which has quite different patterns depending on the bird and their trajectory, after some time an practice it becomes natural and you push the button without even thinking. I do so all the time during Sat. passes.
I think this is the best advice... :)
Greg KO6TH
p.s. All this said in the thread, I am a still bit confused. I thought circular polarization was like nuts & bolts. You can thread the nut on a bolt with either piece in either direction; the thread on them doesn't change just because you picked it up "backwards." I can see the possibility of a reverse polarization in the side lobes, but out the back of the antenna shouldn't it be the same as the main lobe? Or am I nuts (pun intended)? _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb