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
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
_______________________________________________ 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
Maybe I'm not understanding it, but why does one need to switch between both, unless a particular satellite has LHCP or RHCP? Jordan KF5COQ
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
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
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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
_______________________________________________ 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
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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
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
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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
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
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Aha! Most reasonable answer I’ve heard! Thanks!
On Sun, Mar 18, 2018 at 10:21 PM Greg D ko6th.greg@gmail.com wrote:
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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AMSAT-NA.
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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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When you say a satellite "has" RHCP, we have to be careful that we're communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
________________________________________ From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt jmtrewitt@gmail.com Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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
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
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Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com wrote:
When you say a satellite "has" RHCP, we have to be careful that we're communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt jmtrewitt@gmail.com Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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
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
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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 _______________________________________________ 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
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple < jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com
wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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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Try it!
Then it would be clearer to you, practice is just an extension of theory (or vice-versa). Hi!
In our case there many unknown variable that there is no “thumb rule”, it depends obviously on what the birds are doing up there.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 10:33 PM, Burns Fisher burns@fisher.cc wrote:
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple <jean.marc.momple@gmail.com mailto:jean.marc.momple@gmail.com> wrote: Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio <antonio@qti.qualcomm.com mailto:antonio@qti.qualcomm.com> wrote:
When you say a satellite "has" RHCP, we have to be careful that we're communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB <amsat-bb-bounces@amsat.org mailto:amsat-bb-bounces@amsat.org> on behalf of Jordan Trewitt <jmtrewitt@gmail.com mailto:jmtrewitt@gmail.com> Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org mailto:amsat-bb@amsat.org 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? Jordan KF5COQ
On Sun, Mar 18, 2018, 16:34 Eduardo PY2RN <py2rn@arrl.net mailto: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 <mailto:amsat-bb@amsat.org>>To: "amsat-bb@amsat.org mailto:amsat-bb@amsat.org" <amsat-bb@amsat.org mailto: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
Sent via AMSAT-BB@amsat.org mailto: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 http://www.amsat.org/mailman/listinfo/amsat-bb
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I'll say, why not both? I need to get to trying out my cross-pole yagi with my LimeSDR, which should be able to receive two inputs at the same time.
From there I'm assuming I could just set up some phase delays in GNU Radio
and adders to produce both LHCP and RHCP at the same time, in theory at least. Only problem is that I've heard there's some inconsistent phase differences between the two channels. -Jordan KF5COQ
On Mon, Mar 19, 2018 at 2:03 PM Jean Marc Momple jean.marc.momple@gmail.com wrote:
Try it!
Then it would be clearer to you, practice is just an extension of theory (or vice-versa). Hi!
In our case there many unknown variable that there is no “thumb rule”, it depends obviously on what the birds are doing up there.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 10:33 PM, Burns Fisher burns@fisher.cc wrote:
I'd really like to understand this better, but it is still not making
sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves
at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get
better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple <
jean.marc.momple@gmail.com mailto:jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I
need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there
is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be
compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio <
antonio@qti.qualcomm.com mailto:antonio@qti.qualcomm.com> wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB <amsat-bb-bounces@amsat.org <mailto:
amsat-bb-bounces@amsat.org>> on behalf of Jordan Trewitt < jmtrewitt@gmail.com mailto:jmtrewitt@gmail.com>
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org mailto:amsat-bb@amsat.org 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? Jordan KF5COQ
On Sun, Mar 18, 2018, 16:34 Eduardo PY2RN <py2rn@arrl.net <mailto:
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 <mailto:amsat-bb@amsat.org>>
To: "amsat-bb@amsat.org mailto:amsat-bb@amsat.org" <
amsat-bb@amsat.org mailto: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
Sent via AMSAT-BB@amsat.org mailto:AMSAT-BB@amsat.org. AMSAT-NA
makes this open forum available
to all interested persons worldwide without requiring membership.
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of
AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
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I’m not an expert either, but my understanding is that polarization changes result from passage through the ionosphere. It’s impossible to predict how the polarization will change without knowing the state of the ionosphere along the signal path at any given moment.
Emperically, I know that switching the handedness of CP can almost completely eliminate fades (it doesn’t work on all fades, but I suspect the ones not affected are actually signal blockages by the ISS structure). I have experienced this many times while operating the ARISS telebridge station in Maryland. There have also been passes with no noticeable fades, so switching isn’t always necessary.
Dave, W8AAS
On Mar 19, 2018, at 2:33 PM, Burns Fisher burns@fisher.cc wrote:
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple < jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com
wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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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ANy antenna that launches an RHCP wave out the front emits and LHCP wave out the back. That is why all real-world antrennas for gain have a reflector so that the LHCP out the back gets a 180 phase shift and then also goes out the fron RHCP.
But on a small satellite, there is not enough realestate for a huge reflector.
Hence at one orientation, the wave may appear to be RHCP and the people on the other side will see LHCP.
But then this effect is minimal if the antennas are linear on the satellite which most are. BUT if there are dual monopoles on the sateliilte to make it cross polarized, then you do get RHCP and LHCP at the same time. And so there can be nulls. If you use exclusively one or the other on the ground and the satellite orientation changes.
Bob WB4APR
-----Original Message----- From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Burns Fisher Sent: Monday, March 19, 2018 2:33 PM To: Jean Marc Momple jean.marc.momple@gmail.com Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Polarization Question
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple < jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com
wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something
else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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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Hi Burns, Jean Marc and Satellite Fans,
Here is my explanation of why Antenna Polarisation varies: If the satellite is transmitting random linear polarisation then a CP antenna should pick up most of the signal, however remember that a CP antenna uses phasing between the Vertical and Horizontal antennas to determine the sense (RHCP or LHCP) of the circular polarisation. If you consider the satellite to also have Vertical and Horizontal components to its polarisation then how these components change in phase when passing through the ionosphere determines whether RHCP or LHCP will work better.
In addition there is the problem of reflections (ground and adjacent objects) with the receiving antenna. You can see this by looking a plots of the Vertical radiation pattern of antennas at various heights. At the low heights of typical satellite antennas any Horizontal component of the received signal will vary depending on the elevation angle of the satellite. Any Vertical component will be pretty constant. As an example AO-91 seems to work better with Vertical polarisation at low elevation angles and changes to Horizontal at high elevation angles (height above ground 1.5 metres).
So a satellite receiving antenna needs to be able to vary the polarisation to be able to avoid fading at some elevation angles.
73, Terry Osborne ZL2BAC
-----Original Message----- From: Burns Fisher Sent: Tuesday, March 20, 2018 7:33 AM To: Jean Marc Momple Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Polarization Question
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple < jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com
wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
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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
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AMSAT-NA.
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Terry,
I tend to agree with all you mentioned, but there is much more:
1) First, what I wanted to say is that there is not ideal solution for all birds due to the different variables for each bird, such as spinning rate, direction of spinning and antenna placement, type of antenna, Tx power etc… If all parameters not known and without these information it is difficult to calculate the path budget and/or design the best setup for the ground station. 2) I also confirm multi-path is an issue and a good example to illustrate, it is an issue particularly at low angle, more over the sea and at higher frequency it is easily observed, this is well experienced here e.g. AO-92 on L-mode has quite deep fading on the uplink at low angle as compare with same situation on the U/V mode (we are in an small Island and surrounded by sea). 3) How I know that it is on the uplink? It is very simple, the fading is on my voice transmission fade deeply while at the same moment telemetry is received rock solid no difference in signal strength. This an example how observation may help to determine what is the real issue. This is why I advices to Burns to try and he will surely have a better understanding and may experience for himself. 4) There is many techniques well known to correct multi-path fading (keeping this issue as example) such as space diversity etc.. however this complicate the whole installation and not really worth for a HAM station/our purpose. More one can even analyze (with proper test equipment/software) the downlink signal and determine what would be the best polarization for uplink, automate the station, etc… I guess going that way will be a long technical debate beyond the scope of actual discussion. 5) I have take one example, the other variables mentioned such as reflection, obstacles such as trees/buildings etc.. also causing QSB, which are unique to each ground stations, there are also solutions, one should be aware of its own environment and adapt its station design to mitigate same.
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.
Same conclusion as yours.
Hope this help all.
73
Jean Marc
On Mar 20, 2018, at 7:34 AM, Wendy and Terry Osborne wandtosborne@gmail.com wrote:
Hi Burns, Jean Marc and Satellite Fans,
Here is my explanation of why Antenna Polarisation varies: If the satellite is transmitting random linear polarisation then a CP antenna should pick up most of the signal, however remember that a CP antenna uses phasing between the Vertical and Horizontal antennas to determine the sense (RHCP or LHCP) of the circular polarisation. If you consider the satellite to also have Vertical and Horizontal components to its polarisation then how these components change in phase when passing through the ionosphere determines whether RHCP or LHCP will work better.
In addition there is the problem of reflections (ground and adjacent objects) with the receiving antenna. You can see this by looking a plots of the Vertical radiation pattern of antennas at various heights. At the low heights of typical satellite antennas any Horizontal component of the received signal will vary depending on the elevation angle of the satellite. Any Vertical component will be pretty constant. As an example AO-91 seems to work better with Vertical polarisation at low elevation angles and changes to Horizontal at high elevation angles (height above ground 1.5 metres).
So a satellite receiving antenna needs to be able to vary the polarisation to be able to avoid fading at some elevation angles.
73, Terry Osborne ZL2BAC
-----Original Message----- From: Burns Fisher Sent: Tuesday, March 20, 2018 7:33 AM To: Jean Marc Momple Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Polarization Question
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple < jean.marc.momple@gmail.com> wrote:
Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio antonio@qti.qualcomm.com
wrote:
When you say a satellite "has" RHCP, we have to be careful that we're
communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which
transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger
received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB amsat-bb-bounces@amsat.org on behalf of Jordan Trewitt
Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.org 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? Jordan KF5COQ
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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AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
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AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
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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)?
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
At 04:36 PM 3/21/2018, Greg D wrote: 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."
Beautiful visual, but the electromagnetic waves don't work quite like that.
If the waves went IN to the antenna from the back, and came OUT the front, like your bolt, then your picture would be perfect.
The EM waves come OUT both front and back of the transmit antenna, so its a mirror image situation.
If you visualize the electric vector rotating around in the plane of the antenna, just like the second hand of the clock, and then you visualize the wave coming out either side of the antenna, starting at the tip of the second hand and moving away from the antenna at the speed of light, you will see that on one side you get a helix that screws one way, and on the other side you get a helix that screws the other way.
Three dimensional stuff is always difficult to visualize correctly. Its one of the reasons I never took up flying.
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?
Side lobes, back lobes, all names for lobes other than the main forward lobe of an antenna. In general, when there are multiple lobes from a circularly polarized antenna, some of them will have one polarization, and some the other. They alternate, ie the 1st order lobes will be flipped from the main lobe, 2nd order lobes will be flipped from the 1st order lobes, etc.
The simple clock example I gave is most like a simple crossed dipole, which has only front and back lobe. If you have a more complex antenna, which squishes its main beam smaller, it will typically have more lobes, some of which we call side lobes, and yes, those first order side lobes will have polarity reversed from the main beam.
Or am I nuts (pun intended)?
Perhaps its simply a polarizing discussion.
Franklin,
If you indeed have a purchased copy of HRD, I would send your question to HRD support. I would be interested in their response as well
I will probably get stabbed in the eye for saying this, but I for one love the idea of using HRD as an everything program, digital modes, logging, sats, etc. my personal experience on this BBS has been "HRD doesn't work" however I have yet to get anyone to spell out exactly what items don't work. It's always the same general response. I completely understand that purchasing SatPC32 helps support the AMSAT family and that is commendable. However there are some of the most intelligent people on this board that will give you some of the most excellent descriptions of any thing you desire, but ask about HRD, and the answers get foggy. Sorry Drew, you can poke me in the eye with a stick then next Orlando ham-cation. :-)
I would still purchase SatPC32 for 2 reasons: 1. There is an immense support community available which you don't have with HRD. 2. The money spent on SatPC32 helps support your local AMSAT which in the end is what it's all about.
Michael KC4ZVA
On Mar 22, 2018, at 4:42 PM, Franklin Antonio antonio@qti.qualcomm.com wrote:
At 04:36 PM 3/21/2018, Greg D wrote: 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."
Beautiful visual, but the electromagnetic waves don't work quite like that.
If the waves went IN to the antenna from the back, and came OUT the front, like your bolt, then your picture would be perfect.
The EM waves come OUT both front and back of the transmit antenna, so its a mirror image situation.
If you visualize the electric vector rotating around in the plane of the antenna, just like the second hand of the clock, and then you visualize the wave coming out either side of the antenna, starting at the tip of the second hand and moving away from the antenna at the speed of light, you will see that on one side you get a helix that screws one way, and on the other side you get a helix that screws the other way.
Three dimensional stuff is always difficult to visualize correctly. Its one of the reasons I never took up flying.
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?
Side lobes, back lobes, all names for lobes other than the main forward lobe of an antenna. In general, when there are multiple lobes from a circularly polarized antenna, some of them will have one polarization, and some the other. They alternate, ie the 1st order lobes will be flipped from the main lobe, 2nd order lobes will be flipped from the 1st order lobes, etc.
The simple clock example I gave is most like a simple crossed dipole, which has only front and back lobe. If you have a more complex antenna, which squishes its main beam smaller, it will typically have more lobes, some of which we call side lobes, and yes, those first order side lobes will have polarity reversed from the main beam.
Or am I nuts (pun intended)?
Perhaps its simply a polarizing discussion.
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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)?
I'll double down on the explanation I wrote below, because I believe it addresses the issue you're having trouble with. However, I've figured out another way to say the same thing using different perhaps more familiar language. Here goes...
Suppose we have a satellite that transmits (so they say) a Right Hand Circular Polarized signal. That means the electric vector spins around in a counterclockwise direction. Ah, but clockwise is an interesting concept. Lets think about a clock.
Suppose I launched a giant clock into orbit. It is big enough so that you can see it with a telescope, and it has a transparent face. What you see in the telescope are the giant clock hands.
As you look thru the telescope, fred asks you "Which way do the clock hands rotate? Clockwise or counterclockwise?" Now it happens that at this moment the clock is oriented so that you're looking at it from the side. You respond "I don't know. I don't see any rotation. They seem to be going just up and down!"
Then after awhile the clock's orientation has changed a bit, and now you can see rotation. You say "hey, now I see rotation, and it's clockwise!" You are now looking at the front of the clock.
The clock itself is slowly rotating so after awhile you say "Hey, its just going up and down again!" This means that the clock has now rotated so that you're seeing it edge-on again, from the other side.
After another wait you say "Wow, now I see rotation again, but now it's counterclockwise! It changed! How can that be?" This just means you're now seeing the clock from the back instead of the front. When you look from the back side, the clockwise rotation of the clock looks like counterclockwise rotation.
How the signal from an antenna on a spacecraft looks to you works the same way, except we use different names. Clockwise rotation is LHCP. Counterclockwise rotation is RHCP. Up-and-down movement is linear polarization.
If you ask a clock designer which way he built the clock to go, he'll think you're an idiot, and he'll say "clockwise of course". But keep in mind he's speaking under the assumption that you view his clock from the front. He doesn't say this, but he means it nevertheless.
If you ask a designer of an antenna which polarization he designed the antenna to generate, he may say "RHCP", but keep in mind he's speaking under the assumption that you view his antenna from the front (ie in the main beam). If you're viewing from the side or the back, the answer is different.
If you view a transmitting antenna or a clock from a different direction, then you see a different rotation or polarization.
You can write a bunch of complicated equations to describe all this, but at its heart its just simple geometry.
________________________________ From: Burns Fisher burns@fisher.cc Sent: Monday, March 19, 2018 11:33 AM To: Jean Marc Momple Cc: Franklin Antonio; amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Polarization Question
I'd really like to understand this better, but it is still not making sense to me. I believe that if you are transmitting with a CP antenna, the E and M waves actually go through an entire circle in one carrier cycle and a CP antenna is able to "follow" that. Surely a satellite is not spinning at anywhere close to 145 or 450 million revs per second, so I don't get "spinning satellite" as an explanation for why an LHP or RHP antenna might work better at different times.
What I do get is that a CP antenna can receive linearly polarized waves at any angle equally. But this should be true whether the antenna is LHP or RHP, and I would not think which direction should matter if the signal is linear in the first place, even if the signal is spinning slowly.
That all said, I have definitely heard people say that they can get better reception by changing from LHP to RHP. I'm not saying this is not true. Just that I don't understand it.
73,
Burns WB1FJ
On Mon, Mar 19, 2018 at 1:57 PM, Jean Marc Momple <jean.marc.momple@gmail.commailto:jean.marc.momple@gmail.com> wrote: Guys,
Long debate for not much. I have followed this stream and believe that I need to intervene.
It is very simple, most HAM birds does spin (sometimes a lot) and there is no way one can anticipate as different from one bird to others. It is just operator skills (on the spot) to determine/switch from LHCP or RCCP based on what is the best received signal strength. It works both on the Uplink and Downlink. There is no miracle formulae and it is a just operator skills as mentioned before.
For commercial birds it is totally different game and should not be compared with our humble Ham birds, they have much more means to do things that we cannot afford to do, except if all HAM worldwide donate to AMSAT, say $10 we then may be able to match some of the features commercially available.
Just a suggestion and food for thought.
73
Jean Marc (3B8DU)
On Mar 19, 2018, at 8:54 PM, Franklin Antonio <antonio@qti.qualcomm.commailto:antonio@qti.qualcomm.com> wrote:
When you say a satellite "has" RHCP, we have to be careful that we're communicating clearly about what "has" means. Every satellite "has" both, by virtue of he way antennas work.
I suspect that you mean that the satellite has an antenna which transmits RHCP in its main lobe. It is important to realize that the signal from such an antenna is only RHCP in its main lobe. The sidelobes are gonna be LHCP. In between, you can get anything in between. So if a satellite is oriented so that its antenna points right at you, and they designed it to be RHCP, then that's what you're gonna get, but if it is pointing off to the side, then you get something else.
This means that there are situations in which you might get a stronger received signal if you switch to LHCP, or maybe even to linear. In the commercial satellite biz, they design satellites so that their antennas point at the users. Hams build cheaper satellites, which typically don't have sophisticated attitude control, so sometimes they point away from you. Also, hams try to use the things even when conditions aren't the best. If that's your aim, then most folks have found that polarization switching sometimes helps.
From: AMSAT-BB <amsat-bb-bounces@amsat.orgmailto:amsat-bb-bounces@amsat.org> on behalf of Jordan Trewitt <jmtrewitt@gmail.commailto:jmtrewitt@gmail.com> Sent: Sunday, March 18, 2018 2:43 PM To: Eduardo PY2RN Cc: amsat-bb@amsat.orgmailto:amsat-bb@amsat.org 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? Jordan KF5COQ
On Sun, Mar 18, 2018, 16:34 Eduardo PY2RN <py2rn@arrl.netmailto: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<mailto:amsat-bb@amsat.org>>To: "amsat-bb@amsat.orgmailto:amsat-bb@amsat.org" <amsat-bb@amsat.orgmailto: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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Brian,
i have 2 systems for sat: main station has switchable polarisation between RHCP and LHCP and i switch on ALL sat-passes. Tested a system in the past with a switch between H and V, but i like the RHCP/LHCP switching the most because less fading.
sub station is with 2 small crossyagis with a 4 polarisation switch per antenna; most of the time i use at these antennas the RHCP and LHCP position, but it is nice to use the V and H positions as extra,but not needed for sat, only terrestrial for dx and local chat here.It was just a nice thing to make the 4p switch and hoping it should work...and it is.
73's Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" amsat-bb@amsat.org Aan: "amsat-bb" amsat-bb@amsat.org Verzonden: Zondag 18 maart 2018 20:44:48 Onderwerp: [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
_______________________________________________ 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
Brian,
i have 2 systems for sat: main station has switchable polarisation between RHCP and LHCP and i switch on ALL sat-passes. Tested a system in the past with a switch between H and V, but i like the RHCP/LHCP switching the most because less fading.
sub station is with 2 smaller crossyagis with a 4 polarisation switch per antenna; most of the time i use at these antennas the RHCP and LHCP position, but it is nice to use the V and H positions as extra,but not needed for sat, only for terrestrial dx(H) and local chat(V).It was just a nice project to make the 4p switch and hoping it should work...and it is.
73's Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" amsat-bb@amsat.org Aan: "amsat-bb" amsat-bb@amsat.org Verzonden: Zondag 18 maart 2018 20:44:48 Onderwerp: [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
_______________________________________________ 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
participants (14)
-
Brian -
Burns Fisher -
Dave Taylor -
Eduardo PY2RN -
Franklin Antonio -
Greg D -
Jean Marc Momple -
jerry.tuyls＠telenet.be -
jim＠k6ccc.org -
Jordan Trewitt -
Mvivona -
on4cjq＠telenet.be -
Robert Bruninga -
Wendy and Terry Osborne