Another way to understand it is that the if in any given direction the combination of the emission from a cubesat with only one or two antenna elements appears RHCP in one direction, it will appear LHCP in the opposite direction to the same extent.
So during a pass or due to tumbling, you can see both
I think. Bob, WB4aPR
-----Original Message----- From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Greg D Sent: Sunday, March 18, 2018 10:21 PM To: Burns Fisher burns@fisher.cc; Eduardo PY2RN py2rn@arrl.net Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Polarization Question
Hi Burns,
I've experienced that too, and from a little research I think it has more to do with mechanics, and less physics. The thought is that no CP antenna is perfectly circular, and so has a linear component to the pattern. That linear component's alignment, or mis-alignment, with the satellite's antenna causes some fading. Flipping the handedness also changes the angle of that linear part, so it can help (or hurt) the reception.
At least, that's the theory. There may also be reflections from buildings and the planet that will introduce a linear component to the signal, and perhaps some atmospheric effects as well.
Greg KO6TH
Burns Fisher wrote:
Indeed, CP makes sense with a linear tx when you can't tell what the orientation would be. You give up a few dB to avoid deep fades. But I just can't figure out why you need to switch from RHP to LHP in such cases. I've heard a number of people say that it sometimes matters, but I don't understand the physics!
73,
Burns WB1FJ
On Sun, Mar 18, 2018 at 6:06 PM, Eduardo PY2RN py2rn@arrl.net wrote:
Jordan, most of the amateur radio LEOs SATs today have a linear polarized antenna attached, it is not possible to know which position it is in the time of the pass: H, V, moving, spinning... being completely random to the ground station which polarization the signal will be, for this reason I believe CP is more efficient but with RH/LH
switching capability.
73 Ed PY2RN From: Jordan Trewitt jmtrewitt@gmail.com To: Eduardo PY2RN py2rn@arrl.net Cc: Brian cqkg8co@yahoo.com; "amsat-bb@amsat.org" amsat-bb@amsat.org Sent: Sunday, March 18, 2018 6:44 PM Subject: Re: [amsat-bb] Antenna Polarization Question
Maybe I'm not understanding it, but why does one need to switch between both, unless a particular satellite has LHCP or RHCP?JordanKF5COQ
On Sun, Mar 18, 2018, 16:34 Eduardo PY2RN py2rn@arrl.net wrote:
Hi Brian, Both. You are going to need to switch between RHCP and LHCP often during a sat pass. The same happens if using linear polarization (V/H) but in this case the switch between V and H will happen much more
often than in CP.
73 Ed PY2RN
From: Brian via AMSAT-BB <amsat-bb@amsat.org>To: "amsat-bb@amsat.org" amsat-bb@amsat.org Sent: Sunday, March 18, 2018 6:21 PM Subject: [amsat-bb] Antenna Polarization Question
Should I be using LHCP or RHCP when setting up the 2 meter and 440 yagi's to work the LEO's.
Thank you
Brian, KG8CO
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