Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 06/ 5/12 12:26 AM, Magnus Danielson wrote: On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus I can confirm that I'm 100% sure that the polarization of the two antennas needs to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and got appreciate gain. Despite what other may say, there does seem to be a lot of confusion about this issue, but I've satisfied myself by building them and testing the gain using a VNA as the signal source and detector. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 07/07/2012 06:21 PM, Dr. David Kirkby wrote: On 06/ 5/12 12:26 AM, Magnus Danielson wrote: On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus I can confirm that I'm 100% sure that the polarization of the two antennas needs to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and got appreciate gain. Despite what other may say, there does seem to be a lot of confusion about this issue, but I've satisfied myself by building them and testing the gain using a VNA as the signal source and detector. We had this straighten out about a month ago, and me posting more or less as I landed from a transatlantic flight wasn't optimum (tired and waving hands didn't help, as I got it wrong). RHCP should match RHCP and LHCP should match LHCP. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 07/ 7/12 05:43 PM, Magnus Danielson wrote: On 07/07/2012 06:21 PM, Dr. David Kirkby wrote: I can confirm that I'm 100% sure that the polarization of the two antennas needs to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and got appreciate gain. Despite what other may say, there does seem to be a lot of confusion about this issue, but I've satisfied myself by building them and testing the gain using a VNA as the signal source and detector. We had this straighten out about a month ago, and me posting more or less as I landed from a transatlantic flight wasn't optimum (tired and waving hands didn't help, as I got it wrong). RHCP should match RHCP and LHCP should match LHCP. Cheers, Magnus I must admit, I was pretty convinced a month ago they should match, but there is nothing like actually verifying something experimentally. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 7/7/12 9:21 AM, Dr. David Kirkby wrote: I can confirm that I'm 100% sure that the polarization of the two antennas needs to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and got appreciate gain. Despite what other may say, there does seem to be a lot of confusion about this issue, but I've satisfied myself by building them and testing the gain using a VNA as the signal source and detector. Nothing like an actual test to clarify things, eh? wind one for LHCP and you can play with the reversal after a reflection.. In the latest Ant and Prop Magazine there's an article about a antenna lab with demos from Cal Poly SLO. Very cool.. all at 900 MHz, so things are small, but not so small that skin depth and precision measurements come into place. Lots of different kinds of antennas, and they built a nice little LED bargraph signal strength display. Reminiscent of a video taped lecture from Kraus that I saw. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
Thanks for clearing up any confusion Magnus, one more question, are the any conditions such as reflected signals that can reverse polarization? Thomas Knox Date: Sat, 7 Jul 2012 18:43:10 +0200 From: mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer On 07/07/2012 06:21 PM, Dr. David Kirkby wrote: On 06/ 5/12 12:26 AM, Magnus Danielson wrote: On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus I can confirm that I'm 100% sure that the polarization of the two antennas needs to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and got appreciate gain. Despite what other may say, there does seem to be a lot of confusion about this issue, but I've satisfied myself by building them and testing the gain using a VNA as the signal source and detector. We had this straighten out about a month ago, and me posting more or less as I landed from a transatlantic flight wasn't optimum (tired and waving hands didn't help, as I got it wrong). RHCP should match RHCP and LHCP should match LHCP. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
Exactly. Reflections reverse the cp sense On Jul 7, 2012, at 11:40, Tom Knox act...@hotmail.com wrote: Thanks for clearing up any confusion Magnus, one more question, are the any conditions such as reflected signals that can reverse polarization? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 07/07/2012 08:49 PM, Jim Lux wrote: Exactly. Reflections reverse the cp sense On Jul 7, 2012, at 11:40, Tom Knoxact...@hotmail.com wrote: Thanks for clearing up any confusion Magnus, one more question, are the any conditions such as reflected signals that can reverse polarization? Thomas Knox This allows a first degree surpression of multipath signals for GPS. Choke ring and then damping material on the backside also helps. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 5 June 2012 01:12, Dave Martindale dave.martind...@gmail.com wrote: I don't think that's correct. This is a funny topic. No matter where see it discussed, there are people with different views on it. I looked on the edaforum http://www.edaboard.com/forum26.html and found a thread (can't find it now unfortunatey), where someone was adament they needed to be one way (I forget whether both RHCP or RHCP+LHCP), and someone else was adament a colleague nearly lost his job after making that mistake. I think there was about a 50:50 mix of views on the topic I think I might have to make 3 axial mode helical antennas and test this myself. If I wind two in one way, and one in another, it should be possible to determine if the strongest signal is received with them wound the same way, or wound the opposite way. I don't know much about helix antenna design, but I know there are two modes - normal and axial. I have some software able to design either, as well as some complex types. Sticking a frequency of 300 MHz (so lambda is a convenient 1 m), I get: Normal mode: helix diamater 0.05 lambda, helix spacing 0.05 lambda. 1.818 turns (no option to set gain). Axial mode: helix diameter 0.318 lambda, helix spacing 0.222 lambda, 3.341 turns for 10 dBi gain, 6.667 for 13 dBi, 13.302 turns for 16 dBi and 26.541 for 19 dBi and 33.413 turns for 20 dBi. So the diameter of the helix does not tell you much on its own, as there are two different types, one of which has a very different diameter to the other. Note the axial mode helix has a diameter of 0.318 lambda, so a circumference of Pi*0.318 = 1.0 lambda. I think there is some story that when Krauss invented this antenna, he made the first one with a circumference of 1 wavelength, and more by luck than anything else, got it right first time. (Note, this software is designed to create a model for a 3D electromagnetic simulator, so the results are not perfect, and one is expected to tweak the design using the 3D electromagetic simulator). Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
I guarantee you it doesn't cause any controversy among those that use circularly polarized antennas. That the polarization changes from RHCP to LHCP when reflected is certainly the cause of some confusion about the antennas. A RHCP antenna that directly emits a wave towards the source will become a LHCP antenna if it is illuminating a parabolic dish. The easiest way to think about it is to mentally think of the path from the transmitter to the receiver as a very long piece of threaded rod, and the wave being emitted as being a nut traveling on the rod. No matter which side of the rod you are observing from, you will observe a nut traveling away from that end turning in the same direction (clockwise for RHCP). Another point of confusion could be that if you are standing at the transmitter watching the nut travel away from you, it will be rotating clockwise but if you are standing at the receiver watching the nut traveling towards you, it will be rotating counter-clockwise. Both cases are RHCP. If I hired an engineer to work on circularly polarized antennas and he didn't know this, I too would be thinking of firing him! -Chuck Harris David Kirkby wrote: On 5 June 2012 01:12, Dave Martindaledave.martind...@gmail.com wrote: I don't think that's correct. This is a funny topic. No matter where see it discussed, there are people with different views on it. I looked on the edaforum http://www.edaboard.com/forum26.html and found a thread (can't find it now unfortunatey), where someone was adament they needed to be one way (I forget whether both RHCP or RHCP+LHCP), and someone else was adament a colleague nearly lost his job after making that mistake. I think there was about a 50:50 mix of views on the topic ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
The easiest way to think about it is to mentally think of the path from the transmitter to the receiver as a very long piece of threaded rod, and the wave being emitted as being a nut traveling on the rod. Ah, and each of the photons then becomes a time nut. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
Tom Van Baak wrote: The easiest way to think about it is to mentally think of the path from the transmitter to the receiver as a very long piece of threaded rod, and the wave being emitted as being a nut traveling on the rod. Ah, and each of the photons then becomes a time nut. Of course! I forgot to mention that the nut is spinning, not the rod... So it is not just a timenut, but a spinning timenut. -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
I took a scan through Kraus Antennas since he did much of the definitive work on Helical antennas. In his chapter on Wave Polarization he gives a mathematical definition of Left- and Right-circular polarization, then quickly mentions that the IEEE definition is the opposite. He has a footnote: This IEEE definition is opposite to the classical optics definition. So it seems our current antenna engineering uses the IEEE definition for RHCP and LHCP, but earlier work on EM wave theory had defined right-circular and left-circular exactly reversed from IEEE. So, combine that with the reflection flipping and it is not hard to think why there might be confusion. I looked all around for a simple definition of the RH, LH quality of the wave from a helix antenna. I assume I might have extracted it from pages of formulas and theoretical explanations, but why not just clearly state it in a book that is largely about helical antennas. Somewhere else (in Kraus) I read that the IEEE definition of a RHCP or LHCP wave from or to a helical antenna had the same handedness as the helix of the antenna. Unfortunately in that writing he did not bother to explicitly mention what he meant by the handedness of a helix. I assume he meant it to be the same as the handedness of a screw, but he didn't say that, so once again, a missed opportunity. I'm not arguing with you, Chuck, just pointing out why there might be room for confusion in some circles. (Pun intended.) On 6/5/2012 6:23 AM, Chuck Harris wrote: I guarantee you it doesn't cause any controversy among those that use circularly polarized antennas. That the polarization changes from RHCP to LHCP when reflected is certainly the cause of some confusion about the antennas. A RHCP antenna that directly emits a wave towards the source will become a LHCP antenna if it is illuminating a parabolic dish. The easiest way to think about it is to mentally think of the path from the transmitter to the receiver as a very long piece of threaded rod, and the wave being emitted as being a nut traveling on the rod. No matter which side of the rod you are observing from, you will observe a nut traveling away from that end turning in the same direction (clockwise for RHCP). Another point of confusion could be that if you are standing at the transmitter watching the nut travel away from you, it will be rotating clockwise but if you are standing at the receiver watching the nut traveling towards you, it will be rotating counter-clockwise. Both cases are RHCP. If I hired an engineer to work on circularly polarized antennas and he didn't know this, I too would be thinking of firing him! -Chuck Harris David Kirkby wrote: On 5 June 2012 01:12, Dave Martindaledave.martind...@gmail.com wrote: I don't think that's correct. This is a funny topic. No matter where see it discussed, there are people with different views on it. I looked on the edaforum http://www.edaboard.com/forum26.html and found a thread (can't find it now unfortunatey), where someone was adament they needed to be one way (I forget whether both RHCP or RHCP+LHCP), and someone else was adament a colleague nearly lost his job after making that mistake. I think there was about a 50:50 mix of views on the topic ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
To quote Jasik's treatment of Kraus's work: There are two kinds of circular polarization, right-hand, and left-hand. Either type may be generated by a helical beam antenna, depending on the manner in which the helix is wound. A helix wound like a right-hand screw radiates or receives right-hand circular polarization... Pretty clear in Jasik. I have to believe that Kraus was able to make a statement with a similar level of clarity somewhere in his book... but I don't have a copy on hand to test my beliefs. As to the thread handedness: That is pretty old terminology that has been around since the first blacksmith tried to describe how he made his screws to another blacksmith. In any case, the handedness of a circularly polarized wave is really just a convention. If the person discussing the principal understands the principal, he should arrive at descriptions that are self consistent. Believing that a RHCP antenna transmits with a right hand helix, and receives with a left hand helix is not being consistent. Either the frame of reference is inconsistent, or the understanding is inconsistent. Right? -Chuck Harris PS, I don't see this as arguing, just two friends having a discussion. Rex wrote: I took a scan through Kraus Antennas since he did much of the definitive work on Helical antennas. In his chapter on Wave Polarization he gives a mathematical definition of Left- and Right-circular polarization, then quickly mentions that the IEEE definition is the opposite. He has a footnote: This IEEE definition is opposite to the classical optics definition. So it seems our current antenna engineering uses the IEEE definition for RHCP and LHCP, but earlier work on EM wave theory had defined right-circular and left-circular exactly reversed from IEEE. So, combine that with the reflection flipping and it is not hard to think why there might be confusion. I looked all around for a simple definition of the RH, LH quality of the wave from a helix antenna. I assume I might have extracted it from pages of formulas and theoretical explanations, but why not just clearly state it in a book that is largely about helical antennas. Somewhere else (in Kraus) I read that the IEEE definition of a RHCP or LHCP wave from or to a helical antenna had the same handedness as the helix of the antenna. Unfortunately in that writing he did not bother to explicitly mention what he meant by the handedness of a helix. I assume he meant it to be the same as the handedness of a screw, but he didn't say that, so once again, a missed opportunity. I'm not arguing with you, Chuck, just pointing out why there might be room for confusion in some circles. (Pun intended.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 06/ 5/12 04:06 PM, Rex wrote: I took a scan through Kraus Antennas since he did much of the definitive work on Helical antennas. In his chapter on Wave Polarization he gives a mathematical definition of Left- and Right-circular polarization, then quickly mentions that the IEEE definition is the opposite. He has a footnote: This IEEE definition is opposite to the classical optics definition. That's basically what Wikipedia says about the optics. They don't reference it, so if it is referenced in Krauss, that would be a worthwhile reference. Most antenna people seem to accept the standard definitions as being IEEE Standard Definitions for Terms of Antennas IEEE Std 145-1983 So it seems our current antenna engineering uses the IEEE definition for RHCP and LHCP, but earlier work on EM wave theory had defined right-circular and left-circular exactly reversed from IEEE. So, combine that with the reflection flipping and it is not hard to think why there might be confusion. I'm not saying Chuck is wrong about one needing the same sense at each end, but I would disagree with him when he says I guarantee you it doesn't cause any controversy among those that use circularly polarized antennas. There certainly is a lot of confusion over this topic, even among people who design them. I don't think the confusion is related to reflections (everyone seems to know that) and I don't think it's related to different conventions either. I was going to try to simulate this by putting two helix antennas and coupling them. But setting that up is a lot more difficult for me than just building three antennas. I looked all around for a simple definition of the RH, LH quality of the wave from a helix antenna. I assume I might have extracted it from pages of formulas and theoretical explanations, but why not just clearly state it in a book that is largely about helical antennas. Somewhere else (in Kraus) I read that the IEEE definition of a RHCP or LHCP wave from or to a helical antenna had the same handedness as the helix of the antenna. Quality of polarization is a very complex topic. See the paper: The definition of cross polarization Antennas and Propagation, IEEE Transactions on Date of Publication: Jan 1973 Author(s): Ludwig, A. California Institute of Technology, Pasadena, CA, USA Volume: 21 , Issue: 1 Page(s): 116 - 119 I've reprinted the abstract below for completeness, though you can read it on the IEEE site without paying. --- Abstract There are at least three different definitions of cross polarization used in the literature. The alternative definitions are discussed with respect to several applications, and the definition which corresponds to one standard measurement practice is proposed as the best choice. --- I printed off a copy of that paper with the intension of trying to understand it. I think the maths gets a bit heavy for me, but the more difficult problem is I was unable to read the small symbols on A4 paper. So it looks as though I'll have to read it on a computer and hope the quality is good enough. Unfortunately in that writing he did not bother to explicitly mention what he meant by the handedness of a helix. I assume he meant it to be the same as the handedness of a screw, but he didn't say that, so once again, a missed opportunity. I'm not arguing with you, Chuck, just pointing out why there might be room for confusion in some circles. (Pun intended.) One method of logically arguing for both antennas to be the same is reciprocity theorem. So I think Chuck is right on the engineering facts, but is wrong about the level of confusion it causes. I wish I could find the post on the EDA forum, as there were many people making arguments for both cases. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
Hi David, Since I apparently have no cred, I can give you a quote from Jasik: A right hand helical antenna transmits or receives right-hand polarization while a left-hand helical antenna will transmit or receive left-hand polarization. Jasik, Antenna Engineering Handbook, First Edition, p17-3. Which seem fairly clear to me. In my experience, there really is no confusion about that among *competent* antenna engineers... among those less schooled in the subject, any amount of confusion is not only possible, but probable. I could see how one could be confused about the definition, as it is purely a matter of convention. That RHCP is defined as the wave propagating in the clockwise direction as viewed from the source could just as easily have been defined as being viewed looking towards the source... but, since the current convention was defined by the IRE more than half a century ago. It shouldn't be all that controversial anymore. -Chuck Harris Dr. David Kirkby wrote: On 06/ 5/12 04:06 PM, Rex wrote: I took a scan through Kraus Antennas since he did much of the definitive work on Helical antennas. In his chapter on Wave Polarization he gives a mathematical definition of Left- and Right-circular polarization, then quickly mentions that the IEEE definition is the opposite. He has a footnote: This IEEE definition is opposite to the classical optics definition. That's basically what Wikipedia says about the optics. They don't reference it, so if it is referenced in Krauss, that would be a worthwhile reference. Most antenna people seem to accept the standard definitions as being IEEE Standard Definitions for Terms of Antennas IEEE Std 145-1983 So it seems our current antenna engineering uses the IEEE definition for RHCP and LHCP, but earlier work on EM wave theory had defined right-circular and left-circular exactly reversed from IEEE. So, combine that with the reflection flipping and it is not hard to think why there might be confusion. I'm not saying Chuck is wrong about one needing the same sense at each end, but I would disagree with him when he says I guarantee you it doesn't cause any controversy among those that use circularly polarized antennas. There certainly is a lot of confusion over this topic, even among people who design them. I don't think the confusion is related to reflections (everyone seems to know that) and I don't think it's related to different conventions either. I was going to try to simulate this by putting two helix antennas and coupling them. But setting that up is a lot more difficult for me than just building three antennas. I looked all around for a simple definition of the RH, LH quality of the wave from a helix antenna. I assume I might have extracted it from pages of formulas and theoretical explanations, but why not just clearly state it in a book that is largely about helical antennas. Somewhere else (in Kraus) I read that the IEEE definition of a RHCP or LHCP wave from or to a helical antenna had the same handedness as the helix of the antenna. Quality of polarization is a very complex topic. See the paper: The definition of cross polarization Antennas and Propagation, IEEE Transactions on Date of Publication: Jan 1973 Author(s): Ludwig, A. California Institute of Technology, Pasadena, CA, USA Volume: 21 , Issue: 1 Page(s): 116 - 119 I've reprinted the abstract below for completeness, though you can read it on the IEEE site without paying. --- Abstract There are at least three different definitions of cross polarization used in the literature. The alternative definitions are discussed with respect to several applications, and the definition which corresponds to one standard measurement practice is proposed as the best choice. --- I printed off a copy of that paper with the intension of trying to understand it. I think the maths gets a bit heavy for me, but the more difficult problem is I was unable to read the small symbols on A4 paper. So it looks as though I'll have to read it on a computer and hope the quality is good enough. Unfortunately in that writing he did not bother to explicitly mention what he meant by the handedness of a helix. I assume he meant it to be the same as the handedness of a screw, but he didn't say that, so once again, a missed opportunity. I'm not arguing with you, Chuck, just pointing out why there might be room for confusion in some circles. (Pun intended.) One method of logically arguing for both antennas to be the same is reciprocity theorem. So I think Chuck is right on the engineering facts, but is wrong about the level of confusion it causes. I wish I could find the post on the EDA forum, as there were many people making arguments for both cases. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
I don't think that's correct. A right-hand spiral (however you define right-hand) remains right-handed if you rotate the whole object in space so the centre axis of the spiral points in the opposite direction. A right-handed spiral is converted to a left-handed one only by reflecting it in a mirror. Try this: pick up two identical bolts. Think of the bolt heads as the feed end of the antenna, with the threads being the helical element. Rotate the two bolts so they are aligned on the same axis, but facing each other. Note that the threaded portions of both bolts spiral the same way. So two identical antennas will work fine as a transmit/receive pair over an open-space path. But if you bounce a RHCP signal off some passive reflector, the signal becomes LHCP (or vise versa), and the transmit and receive antennas need to be mirror images of each other. Dave On Mon, Jun 4, 2012 at 7:26 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/**Circular_polarizationhttp://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer
Not quite. The definition of right-hand circular polarization, as standardized by the IRE... is as follows: For an observer looking in the direction of propagation, the rotation of the electric-field vector in a transverse plane is clockwise. - Jasik, Antenna Engineering Handbook, First Edition, p17-3 A right-hand circularly polarized antenna both transmits and receives RHCP. What is confusing people is a reflection of a RHCP wave is a LHCP wave. -Chuck Harris Magnus Danielson wrote: On 05/06/12 00:30, Dr. David Kirkby wrote: This is not exactly a time related question, but I'm sure the subject must be of interest to time-nuts using GPS. If one transmits from an antenna such as a helical one, RHCP, can the same antenna be used for reception, or does the helix need to be wound the other way? If you google this topic, there seems to be a lot of confusion about whether the TX antenna and RX antenna need to both have RHCP or whether one needs to be LHCP and the other RHCP. Given GPS uses circular polarization, I'm hoping someone here will know. It would appear there are different definitions of circular polarization, with one considering it from the point of view of the source, and the other considering it from the point of view of the receiver. The IEEE apparently uses the former, and others (especially optics) use the opposite. http://en.wikipedia.org/wiki/Circular_polarization My aim was to make a gain measurement of two circular polarized antennas. I have two identical antennas, but are unsure if the signals should be received strongly, or whether theoretically no signal would be received. (Of course in practice, one never achieves perfect polarization, so there will always be a signal detected, even if cross-polarized. They would have to have opposite rotation. The waveform rotation will follow the transmitter antenna into the receiver antenna. The receiver antenna follows the same rotation that the transmitter antenna has, it's just that the face each other, so when you turn one of the 180 degrees such that they face the same direction you would see that they are in fact rotated in opposite directions. I'm sure the sat folks can confirm this. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
