Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nutcan answer
On 6/4/12 10:44 PM, Chris Albertson wrote: On Mon, Jun 4, 2012 at 10:18 PM, Hal Murrayhmur...@megapathdsl.net wrote: What is the significance of the pointy tops of the long skinny antennas? Guessing. Terminates the end of the conductor to prevent a discontinuity and reflection more likely it's for structural reasons. A lot of helical antennas are a wire or tape on a cruciform cross section core (rather than on a tube). You don't want that corner sticking out. On the tube, it's easier to make a cone end, then a flat pillbox, and you don't have the diaphragm vibration mode on the flat end. How about the collars at the base of them? Another guess: They kill multi path reflections from supporting structure or provide a better match. Or both.. An awful lot of antenna designs out there work about the same, particularly for endfire helicals, so if you have a design that works in one application and you want to change it, you might just scale for size, rather than trying to come up with a completely new design. it's like the HeliBowl antennas.. Turns out they're totally non critical and they all work just about the same. Plastic party cup and cheap mixing bowl, and you're in business. Broadside short helices, particularly quad helices are a bit trickier, especially if you're using the one pair a bit long and the other pair a bit short to get the 90 degree phasing. ___ 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-nutcan answer
On Mon, 04 Jun 2012 23:11:14 -0700 Jim Lux jim...@earthlink.net wrote: On 6/4/12 10:44 PM, Chris Albertson wrote: On Mon, Jun 4, 2012 at 10:18 PM, Hal Murrayhmur...@megapathdsl.net wrote: What is the significance of the pointy tops of the long skinny antennas? Guessing. Terminates the end of the conductor to prevent a discontinuity and reflection Or maybe better adaption to free space impedance more likely it's for structural reasons. A lot of helical antennas are a wire or tape on a cruciform cross section core (rather than on a tube). You don't want that corner sticking out. On the tube, it's easier to make a cone end, then a flat pillbox, and you don't have the diaphragm vibration mode on the flat end. Do you mean that the end of the cruciform helix does vibrate and that a cone that ties the end at the center is free of that vibration? How about the collars at the base of them? Another guess: They kill multi path reflections from supporting structure or provide a better match. Or both.. According to a paper on GPS i've read recently, it's to better control the side and back lobes of the signal. The graphs showed quite some improvement of the radiation pattern. If anyone is interested, i can look up the name of the paper. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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-nutcan answer
Hi: I've used an L band amplifier and a passive GPS receive antenna as the transmitting antenna to make a GPS repeater. It was feed from an outside GPS antenna. This allowed having a number of hand held GPS receivers sitting side by side working inside. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Clarke4Congress.html ___ 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-nutcan answer
David, One of these two photos is correct (odd isn't it)... http://www.ausairpower.net/Block-IIR-M-SV-1S.jpg http://www.ausairpower.net/Block-IIR-M-SV-2S.jpg Maybe these break the tie: http://www.spacemankind.com/images/ms/20090817-lockheed-gps-iir-lr.jpg https://share.sandia.gov/news/resources/releases/2008/images/GPS1.jpg http://www.lockheedmartin.com/content/dam/lockheed/data/space/photo/pressrelease/GPS_4A_pr.jpg http://www.insidegnss.com/auto/popupimage/GPSIIF_photo_lo.jpg http://www.freepatentsonline.com/6653987-0-large.jpg /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-nutcan answer
This is a subject I have some familiarity with. A helix antenna which is right hand for receive is also right hand for transmit. Think of it this way. If you have a bolt with a nut on it and you turn the nut to the right it will move along the bolt away from you. If you turn the bolt around so you are looking at the other end and turn the nut to the right it will move away from you. For your transmit antenna the waves are moving away from you and turning to the right. For the other guy's receive antenna the waves are turning to the right and moving away from you. It's the same if you think of yourself as the receive guy and the other guy as transmitting. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Dr. David Kirkby david.kir...@onetel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, June 04, 2012 5:30 PM Subject: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nutcan 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. ___ 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-nutcan answer
Well, they could be consistent. Most of those photos show only two sizes of helix-type antennas. The larger diameter (probably lower frequency) are quadrifilar helix designs, and they are uniformly left hand thread helixes. (I assume that everyone agrees on what a left-hand thread looks like, no matter how they label circular polarization). The more numerous smaller diameter antennas are multi-turn one-element helixes, and they always seem to be right hand thread in all of the photos. The smaller antennas are almost certainly for L1. The complication is the Block-IIR-M-SV-2S photo. But it has *three* sizes of antennas visible. The largest are left-hand-thread quadhelix as before, and thus likely close to the same physical dimensions as the large antennas in the other photos. The mid-size ones are multi-element multi-turn helixes that look a lot like the quadhelixes in design except that the ends are left open. And they are about 2/3 the diameter of the quadhelixes, much larger than the simple helix antennas in the previous group, so probably for a different frequency. Then there are the smallest antennas, which appear to be a single-element helix with many many turns - but these are about 1/3 the diameter of the large quadhelixes, and thus *these* are likely the L1 antennas. And, if I look closely, these small helixes do appear to be right-hand-thread wound. Dave On Mon, Jun 4, 2012 at 8:24 PM, Tom Van Baak t...@leapsecond.com wrote: David, One of these two photos is correct (odd isn't it)... http://www.ausairpower.net/Block-IIR-M-SV-1S.jpg http://www.ausairpower.net/Block-IIR-M-SV-2S.jpg Maybe these break the tie: http://www.spacemankind.com/images/ms/20090817-lockheed-gps-iir-lr.jpg https://share.sandia.gov/news/resources/releases/2008/images/GPS1.jpg http://www.lockheedmartin.com/content/dam/lockheed/data/space/photo/pressrelease/GPS_4A_pr.jpg http://www.insidegnss.com/auto/popupimage/GPSIIF_photo_lo.jpg http://www.freepatentsonline.com/6653987-0-large.jpg /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. ___ 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-nutcan answer
On 05/06/12 04:51, Dave Martindale wrote: Well, they could be consistent. Most of those photos show only two sizes of helix-type antennas. The larger diameter (probably lower frequency) are quadrifilar helix designs, and they are uniformly left hand thread helixes. (I assume that everyone agrees on what a left-hand thread looks like, no matter how they label circular polarization). The more numerous smaller diameter antennas are multi-turn one-element helixes, and they always seem to be right hand thread in all of the photos. The smaller antennas are almost certainly for L1. The complication is the Block-IIR-M-SV-2S photo. But it has *three* sizes of antennas visible. The largest are left-hand-thread quadhelix as before, and thus likely close to the same physical dimensions as the large antennas in the other photos. The mid-size ones are multi-element multi-turn helixes that look a lot like the quadhelixes in design except that the ends are left open. And they are about 2/3 the diameter of the quadhelixes, much larger than the simple helix antennas in the previous group, so probably for a different frequency. Then there are the smallest antennas, which appear to be a single-element helix with many many turns - but these are about 1/3 the diameter of the large quadhelixes, and thus *these* are likely the L1 antennas. And, if I look closely, these small helixes do appear to be right-hand-thread wound. Well, the traditional Block-II antennas had an inner and and outer ring, at it was made so on purpose to create a antenna-lobe such that it would direct more power towards the edge of the globe than straight down, such that the distance difference and hence the damping is first degree compensated such that the signal strength depending on azimuth is more even. I could dig up the reference if I where at home, but I recall it since I think it is kind of neat engineering. Good that you guys set me straight on the orientation-stuff. 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-nutcan answer
t...@leapsecond.com said: http://www.ausairpower.net/Block-IIR-M-SV-1S.jpg What is the significance of the pointy tops of the long skinny antennas? How about the collars at the base of them? -- These are my opinions. I hate spam. ___ 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-nutcan answer
Slightly off-topic, the first time I was aware of polarisation error was during the very first trans-Atlantic TV tests. On the first night, signals were fine in France (who had a copy of the US antenna), but poor in the UK who had designed and built their own antenna). UK changed polarisation for the next night and signals were then fine. All this live on public TV (when everyone watched, and there we're 500 poor-quality channels vying for your attention). http://www.smecc.org/w_j_bray_-_uk.htm http://www.rfcmd.com/index.php?option=com_contentview=articleid=305%3Athe-first-satellite-dish-catid=56%3AtelecommunicationsItemid=18lang=en Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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-nutcan answer
On Mon, Jun 4, 2012 at 10:18 PM, Hal Murray hmur...@megapathdsl.net wrote: What is the significance of the pointy tops of the long skinny antennas? Guessing. Terminates the end of the conductor to prevent a discontinuity and reflection How about the collars at the base of them? Another guess: They kill multi path reflections from supporting structure Now let's see what the experts say Chris Albertson Redondo Beach, California ___ 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.
