Re: [time-nuts] Choke Ring Design for L1
Steve I tried several Positions and directions and sizes of antennas and pie pans. Usually best was with antenna sitting on the pan with lip up, But not always. Attached is the RIGHT position for one of the best cheap ones I tried. My earlier recommendation for a cheap good working GPS PiePan antenna This is attached to a PBC pipe raised just above my roof line ws Warren, I'm not trying to be a wise guy, but what direction is "right" other than up? Steve At 08:46 PM 3/13/2010, WarrenS wrote: ** All true, BUT... Just put an 8 inch pie pan in the right place, facing the right direction. ws *** <>___ 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] Choke Ring Design for L1
Hi Some basic GPS math: L1 is at: 1575.42 MHz 190.5 mm wavelength 47.625 mm 1/4 wave 1.875 inch 1/4 wave If you are after a 1/4 wave with a short at the bottom, starting from a 2" pan sounds like a good idea. Since you always have fringe effects, 1.875 probably isn't the point you get maximum benefit. Most of the people in the attached reference are running 2.5". I doubt that's because they got the math wrong For a true short at the bottom, you would have to do something about the pan bottoms really connecting well with each other. A "not quite short" at the bottom will give you a "not quite open" at the top. It still will attenuate, just not as much. Lots of pop rivets Bob On Mar 13, 2010, at 8:10 PM, jmfranke wrote: > For detailed measurements of six different choke ring GPS antennas, see; > > http://facility.unavco.org/project_support/permanent/equipment/antennas/ant_cals.html > > > John WA4WDL > > -- > From: "WarrenS" > Sent: Saturday, March 13, 2010 7:46 PM > To: "Discussion of precise time and frequency measurement" > > Subject: Re: [time-nuts] Choke Ring Design for L1 > >> >> All true, >> BUT >> Just to keep from being mislead, >> I said what a choke ring antenna does, >> You have described how it is so good at its job. >> >> The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned >> thingies, around the antenna is to keep reflected Signals from BELOW the >> antenna from sneaking around into the antenna. It does not effect the >> signals above the 10 deg or so elevation point. >> The choke rings are a necessary to get cm type survey accuracy, >> but a pie pan shield /ground plane pretty much does the same thing at the >> GPSDO 1ns (1ft) level, >> where you don't need 100 db rejection for signals below the antenna. >> >> What I've found; don't even need to be lucky. >> Just put an 8 inch pie pan in the right place, facing the right direction. >> >> ws >> *** >> Hi there, >> >> just to prevent from making mistakes ... >> >> You can have two different accessories for GNSS antennas: >> 1) a ground plane >> it prevents the antenna from receiving signals from beneath the >> antenna (from the ground, roof or whatever is beneath) >> ... so this could be your pie pan normally >> 2) a choke ring >> it creates an area of high impedance around your antenna; >> because it is just a (set of) simple quarter wave waveguide(s) with >> short-circuit on one end, you can build it from a sheet of metal by >> yourself; you only need to calculate the sizes for your waveguide on >> the L1 frequency ... and if you are a lucky guy and your pie pan fits >> these sizes, you probably can use it for that ;-) >> >> Best regards >> >> Martin >> >> >>> Is there a design for a choke ring to add to my existing L1 GPS antenna ? >> >> Yeah >> If you are using it for GPSDO work where a ns is good enough and you don't >> need cm accuracy, >> It is called a pie pan with its Lip turned up. >> A choke rings blocks reflected signals from below the antenna from effecting >> the signals, a pie pan works pretty good at that also. >> ws >> >> *** >>> Hello The Net: >> >>> Is there a design for a choke ring to add to my existing L1 GPS antenna ? >>> While there may be some variations to the exact dimensions of a choke >>> ring to a specific type of L1 antenna, either patch, helical, etc., >>> I suspect there is some commonality to the design dimensions. >>> I am looking to start construction and I will be using a cheapie >>> patch/puck antenna. >> >> Stan, W1LE >> >> >> ___ >> 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. > ___ 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] Choke Ring Design for L1
Hi Down would be a lot better for rain draining off. Of course most people don't get a lot of rain in the living room Bob On Mar 14, 2010, at 3:14 PM, steve gunsel wrote: > Warren, > > I'm not trying to be a wise guy, but what direction is "right" other than up? > > Steve > > At 08:46 PM 3/13/2010, WarrenS wrote: > >> All true, >> BUT... >> >> Just put an 8 inch pie pan in the right place, facing the right direction. >> >> ws >> *** > > > ___ > 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] Choke Ring Design for L1
Warren, I'm not trying to be a wise guy, but what direction is "right" other than up? Steve At 08:46 PM 3/13/2010, WarrenS wrote: All true, BUT... Just put an 8 inch pie pan in the right place, facing the right direction. ws *** ___ 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] Choke Ring Design for L1
What I have found is if you have a decent view of the sky or even when indoors on an upper shelf, by turning the pie pan lip up, it helps the antenna location placement sensitivity issue. I'll leave it to the antenna Experts speculate on why that is. ws *** Hi That's one of the many things that makes this all a bit tough to work out. Even without a choke ring, a pie plate, or a ground sheet involved you can move a cheap GPS timing antenna 5 feet and see a very real change in plots. Up / down / left / right often the move does not make much sense. I suspect that if the antenna was 500 feet above all local obstructions that would not be true. In more typical "home user" settings it certainly can be. Plotting software has been around for a *long* time.. Bob On Mar 14, 2010, at 5:59 AM, Peter Vince wrote: As I understand it, the GPS signals are circularly polarised, and so surely reflections will reverse the sense of that polarisation such that the antenna will be insensitive to them? Maybe Warren's simple pie dish is working by shielding the antenna from the true MULTI-path reflections, and any direct SINGLE reflections it produces are ignored due to the polarisation reversal? Peter ___ 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] Choke Ring Design for L1
Does someone know which commercial antennas are 3D designs? Sounds like the $200 AeroAntenna version mentioned previously might be a 3d design, although it's a little tough to guess by simply looking at the enclosure and a single drawing. An evaluation of some 3D antennas: http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf Bob Bob Camp wrote: Hi That's one of the many things that makes this all a bit tough to work out. Even without a choke ring, a pie plate, or a ground sheet involved you can move a cheap GPS timing antenna 5 feet and see a very real change in plots. Up / down / left / right often the move does not make much sense. I suspect that if the antenna was 500 feet above all local obstructions that would not be true. In more typical "home user" settings it certainly can be. Plotting software has been around for a *long* time.. Bob On Mar 14, 2010, at 5:59 AM, Peter Vince wrote: As I understand it, the GPS signals are circularly polarised, and so surely reflections will reverse the sense of that polarisation such that the antenna will be insensitive to them? Maybe Warren's simple pie dish is working by shielding the antenna from the true MULTI-path reflections, and any direct SINGLE reflections it produces are ignored due to the polarisation reversal? Peter ___ 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. ___ 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] Choke Ring Design for L1
Hi That's one of the many things that makes this all a bit tough to work out. Even without a choke ring, a pie plate, or a ground sheet involved you can move a cheap GPS timing antenna 5 feet and see a very real change in plots. Up / down / left / right often the move does not make much sense. I suspect that if the antenna was 500 feet above all local obstructions that would not be true. In more typical "home user" settings it certainly can be. Plotting software has been around for a *long* time.. Bob On Mar 14, 2010, at 5:59 AM, Peter Vince wrote: > As I understand it, the GPS signals are circularly polarised, and so > surely reflections will reverse the sense of that polarisation such > that the antenna will be insensitive to them? Maybe Warren's simple > pie dish is working by shielding the antenna from the true MULTI-path > reflections, and any direct SINGLE reflections it produces are ignored > due to the polarisation reversal? > > Peter > > ___ > 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] Choke Ring Design for L1
Peter Vince wrote: As I understand it, the GPS signals are circularly polarised, and so surely reflections will reverse the sense of that polarisation such that the antenna will be insensitive to them? Yes, as a first degree analysis. However, cancellation will not be 100% since neither the wave, the reflection and the antenna is completely according to that theory. Maybe Warren's simple pie dish is working by shielding the antenna from the true MULTI-path reflections, and any direct SINGLE reflections it produces are ignored due to the polarisation reversal? It at least provides the function of the ground plane. Ground-plane only antennas have been widely used in survey applications. There are many ways to improve the situation for a patch antenna. A ground plane is certainly one of the ways. Recall that wavelength is about 19 cm so anything near optimal antenna should be expected to have comparable size. Oh, the choke ring antennas not only suppress reflections from below, but also provides spatial nulls towards the horizon, such that low elevation reflections is also suppressed. The more nulls, the wider lobe and thus lower elevation angle gets can be accepted. For traditional choke rings 3 or 4 is used. I have three rings in mine. 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] Choke Ring Design for L1
Peter Vince wrote: As I understand it, the GPS signals are circularly polarised, and so surely reflections will reverse the sense of that polarisation such that the antenna will be insensitive to them? Maybe Warren's simple pie dish is working by shielding the antenna from the true MULTI-path reflections, and any direct SINGLE reflections it produces are ignored due to the polarisation reversal? Peter But the incident wave is diffracted at the edge of a finite ground plane creating a surface wave that the patch antenna element does respond to. Unless one has a microwave anechoic chamber one has to calculate the antenna response with an EM simulation program. Its not possible to infer an antenna's response to multipath by merely measuring its apparent response pattern to a GPS SV except perhaps when one has a detailed and accurate EM model of the antenna environment. Bruce ___ 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] Choke Ring Design for L1
As I understand it, the GPS signals are circularly polarised, and so surely reflections will reverse the sense of that polarisation such that the antenna will be insensitive to them? Maybe Warren's simple pie dish is working by shielding the antenna from the true MULTI-path reflections, and any direct SINGLE reflections it produces are ignored due to the polarisation reversal? Peter ___ 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] Choke Ring Design for L1
The major flaw in that method is that it doesn't actually make measurements over the entire sphere. Unless you have an independent method of showing that the effective response to signals incident from underneath the antenna are small it also fails to measure the true response in the upper hemisphere. Before and after plots also don't solve that particular measurement problem. Bruce WarrenS wrote: Bruce wrote Those plots give little information about the antenna response to variations in SV elevation directly as the signal strength from theSV also varies with elevation. No account is taken of the SV signal variation with elevation. ws) Correct, but a really Silly comment. Of course for that you compare the before and after plots. BUT, In your zeal to find something to criticize no mater how small, you missed an important point again. These plots are examples that show the whole overall signal strength picture, which can be used to set the Elevation mask among MANY other things. ws *> WarrenS wrote: Bruce wrote: Only for your particular location and antenna. You have no actual idea of how the antenna response is affected by the presence of the cake tin, Those plots give little information about the antenna response to variations in SV elevation directly as the signal strength from the SV also varies with elevation. nor did you specify what sort of antenna you are using with it. (which is no surprise case they are made to be mounted on a metal body.) The latter are all patch antennas which don't work at all well without a ground plane (either an external one or a built in one). Even the thickness of the ground plane makes a difference to the antenna response: http://www.emtalk.com/tut_1.htm http://www.orbanmicrowave.com/The_Basics_Of_Patch_Antennas.pdf http://www.specemc.com/patch.asp http://piers.mit.edu/piersproceedings/download.php?file=cGllcnMyMDA5bW9zY293fDVQNV8xOTI2LnBkZnwwOTAzMTQwODAxMzA= http://ctvr.ie/docs/RF%20Pubs/IEEEVTC_2007_Investigation%20on%20Miniature%20Wideband%20Patch%20Antenna%20.pdf http://140.117.166.1/eehome/ISCOM2005/SubmitPaper/UploadPapers/ISCON05_00100.pdf A patch antenna at the bottom of a cake tin may not have much gain over the elevation range of interest. Your explanation of why this appears to work well is still nonsense. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. That is exactly what I did with the new Lady Heather, You may want to try it for yourself before your unfounded criticizing or look at the attached. No you didnt, no account is taken of the SV signal variation with elevation. ws *** WarrenS wrote: Thanks, Nice set of references as always. OK, so its not 100db, But you may of missed my point yet again. If you think I said that a 10 cent pie pan is a good substitute for a $1000 survey antenna in all applications, I think we all know that would be Nonsense. BUT what may not be known is: that a turned up pie pan under my cheap patch/puck antenna, works about as good as an expensive survey antenna for use with a Tbolt GPSDO, That's not Nonsense, It's a tested fact. Only for your particular location and antenna. Your explanation of why this appears to work well is still nonsense. You have no actual idea of how the antenna response is affected by the presence of the cake tin, nor did you specify what sort of antenna you are using with it. A patch antenna (like your puck) at the bottom of a cake tin that just happens to be a quarter wave deep may not have much gain over the elevation range of interest. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. So I'm not saying there is anything wrong with using a survey antenna on your GPSDO, if you have more money than cents, and you want the last sub ns of performance. But it is not really necessary, there are many many ways to get more bang for the buck, and they would still need to be done first to take advantage of the survey antenna's small improvement when used for a GPSDO. There appears to be a false impression that choke rings remove all Multipath signals. What they do is to remove multipath ground reflected signals from below the antenna, not multipath signals from above it. ws Bruce *** Bruce wrote: Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesn't have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Docum
Re: [time-nuts] Choke Ring Design for L1
Bruce wrote Those plots give little information about the antenna response to variations in SV elevation directly as the signal strength from theSV also varies with elevation. No account is taken of the SV signal variation with elevation. ws) Correct, but a really Silly comment. Of course for that you compare the before and after plots. BUT, In your zeal to find something to criticize no mater how small, you missed an important point again. These plots are examples that show the whole overall signal strength picture, which can be used to set the Elevation mask among MANY other things. ws *> WarrenS wrote: Bruce wrote: Only for your particular location and antenna. You have no actual idea of how the antenna response is affected by the presence of the cake tin, Those plots give little information about the antenna response to variations in SV elevation directly as the signal strength from the SV also varies with elevation. nor did you specify what sort of antenna you are using with it. The latter are all patch antennas which don't work at all well without a ground plane (either an external one or a built in one). Even the thickness of the ground plane makes a difference to the antenna response: http://www.emtalk.com/tut_1.htm http://www.orbanmicrowave.com/The_Basics_Of_Patch_Antennas.pdf http://www.specemc.com/patch.asp http://piers.mit.edu/piersproceedings/download.php?file=cGllcnMyMDA5bW9zY293fDVQNV8xOTI2LnBkZnwwOTAzMTQwODAxMzA= http://ctvr.ie/docs/RF%20Pubs/IEEEVTC_2007_Investigation%20on%20Miniature%20Wideband%20Patch%20Antenna%20.pdf http://140.117.166.1/eehome/ISCOM2005/SubmitPaper/UploadPapers/ISCON05_00100.pdf A patch antenna at the bottom of a cake tin may not have much gain over the elevation range of interest. Your explanation of why this appears to work well is still nonsense. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. That is exactly what I did with the new Lady Heather, You may want to try it for yourself before your unfounded criticizing or look at the attached. No you didnt, no account is taken of the SV signal variation with elevation. ws *** WarrenS wrote: Thanks, Nice set of references as always. OK, so its not 100db, But you may of missed my point yet again. If you think I said that a 10 cent pie pan is a good substitute for a $1000 survey antenna in all applications, I think we all know that would be Nonsense. BUT what may not be known is: that a turned up pie pan under my cheap patch/puck antenna, works about as good as an expensive survey antenna for use with a Tbolt GPSDO, That's not Nonsense, It's a tested fact. Only for your particular location and antenna. Your explanation of why this appears to work well is still nonsense. You have no actual idea of how the antenna response is affected by the presence of the cake tin, nor did you specify what sort of antenna you are using with it. A patch antenna (like your puck) at the bottom of a cake tin that just happens to be a quarter wave deep may not have much gain over the elevation range of interest. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. So I'm not saying there is anything wrong with using a survey antenna on your GPSDO, if you have more money than cents, and you want the last sub ns of performance. But it is not really necessary, there are many many ways to get more bang for the buck, and they would still need to be done first to take advantage of the survey antenna's small improvement when used for a GPSDO. There appears to be a false impression that choke rings remove all Multipath signals. What they do is to remove multipath ground reflected signals from below the antenna, not multipath signals from above it. ws Bruce *** Bruce wrote: Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesn't have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf http://www.weblab.dlr.de/rbrt/pdf/TN_0505.pdf http://www.leica-geosystems.com/downloads123/zz/nrs/AR25/brochures/AR25_Brochure_en.pdf Bruce *** WarrenS wrote: All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from snea
Re: [time-nuts] Choke Ring Design for L1
WarrenS wrote: Bruce wrote: Only for your particular location and antenna. severl cheap car type antennas and a pole mounted timing antenna. May not work as well in other locations or with other types of antennas. (Like under the water or with choke antennas) You have no actual idea of how the antenna response is affected by the presence of the cake tin, updates, Take a look at her new antenna plot capability. Those plots give little information about the antenna response to variations in SV elevation directly as the signal strength from the SV also varies with elevation. nor did you specify what sort of antenna you are using with it. The latter are all patch antennas which don't work at all well without a ground plane (either an external one or a built in one). Even the thickness of the ground plane makes a difference to the antenna response: http://www.emtalk.com/tut_1.htm http://www.orbanmicrowave.com/The_Basics_Of_Patch_Antennas.pdf http://www.specemc.com/patch.asp http://piers.mit.edu/piersproceedings/download.php?file=cGllcnMyMDA5bW9zY293fDVQNV8xOTI2LnBkZnwwOTAzMTQwODAxMzA= http://ctvr.ie/docs/RF%20Pubs/IEEEVTC_2007_Investigation%20on%20Miniature%20Wideband%20Patch%20Antenna%20.pdf http://140.117.166.1/eehome/ISCOM2005/SubmitPaper/UploadPapers/ISCON05_00100.pdf A patch antenna at the bottom of a cake tin may not have much gain over the elevation range of interest. gain, cause by making a directly antenna out of it, cause I get some of the same effects with the pie pan turned the other way. Your explanation of why this appears to work well is still nonsense. blocking out multipath reflections of which I have many, and these reflections tend to case dips in the signal level due to cancellations as the sat moves across the sky. Also adds some gain to some antennas. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. That is exactly what I did with the new Lady Heather, You may want to try it for yourself before your unfounded criticizing or look at the attached. No you didnt, no account is taken of the SV signal variation with elevation. ws *** WarrenS wrote: Thanks, Nice set of references as always. OK, so its not 100db, But you may of missed my point yet again. If you think I said that a 10 cent pie pan is a good substitute for a $1000 survey antenna in all applications, I think we all know that would be Nonsense. BUT what may not be known is: that a turned up pie pan under my cheap patch/puck antenna, works about as good as an expensive survey antenna for use with a Tbolt GPSDO, That's not Nonsense, It's a tested fact. Only for your particular location and antenna. Your explanation of why this appears to work well is still nonsense. You have no actual idea of how the antenna response is affected by the presence of the cake tin, nor did you specify what sort of antenna you are using with it. A patch antenna (like your puck) at the bottom of a cake tin that just happens to be a quarter wave deep may not have much gain over the elevation range of interest. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. So I'm not saying there is anything wrong with using a survey antenna on your GPSDO, if you have more money than cents, and you want the last sub ns of performance. But it is not really necessary, there are many many ways to get more bang for the buck, and they would still need to be done first to take advantage of the survey antenna's small improvement when used for a GPSDO. There appears to be a false impression that choke rings remove all Multipath signals. What they do is to remove multipath ground reflected signals from below the antenna, not multipath signals from above it. ws Bruce *** Bruce wrote: Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesn't have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf http://www.weblab.dlr.de/rbrt/pdf/TN_0505.pdf http://www.leica-geosystems.com/downloads123/zz/nrs/AR25/brochures/AR25_Brochure_en.pdf Bruce *** WarrenS wrote: All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from sneaking around int
Re: [time-nuts] Choke Ring Design for L1
WarrenS wrote: Thanks, Nice set of references as always. OK, so its not 100db, But you may of missed my point yet again. If you think I said that a 10 cent pie pan is a good substitute for a $1000 survey antenna in all applications, I think we all know that would be Nonsense. BUT what may not be known is: that a turned up pie pan under my cheap patch/puck antenna, works about as good as an expensive survey antenna for use with a Tbolt GPSDO, That's not Nonsense, It's a tested fact. Only for your particular location and antenna. Your explanation of why this appears to work well is still nonsense. You have no actual idea of how the antenna response is affected by the presence of the cake tin, nor did you specify what sort of antenna you are using with it. A patch antenna (like your puck) at the bottom of a cake tin that just happens to be a quarter wave deep may not have much gain over the elevation range of interest. The variation in antenna response with elevation needs to be measured/calculated before one can safely conclude that such an antenna is universally useful. So I'm not saying there is anything wrong with using a survey antenna on your GPSDO, if you have more money than cents, and you want the last sub ns of performance. But it is not really necessary, there are many many ways to get more bang for the buck, and they would still need to be done first to take advantage of the survey antenna's small improvement when used for a GPSDO. There appears to be a false impression that choke rings remove all Multipath signals. What they do is to remove multipath ground reflected signals from below the antenna, not multipath signals from above it. ws Bruce *** Bruce wrote: Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesn't have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf http://www.weblab.dlr.de/rbrt/pdf/TN_0505.pdf http://www.leica-geosystems.com/downloads123/zz/nrs/AR25/brochures/AR25_Brochure_en.pdf Bruce *** WarrenS wrote: All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from sneaking around into the antenna. It does not effect the signals above the 10 deg or so elevation point. The choke rings are a necessary to get cm type survey accuracy, but a pie pan shield /ground plane pretty much does the same thing at the GPSDO 1ns (1ft) level, where you don't need 100 db rejection for signals below the antenna. What I've found; don't even need to be lucky. Just put an 8 inch pie pan in the right place, facing the right direction. ws *** Hi there, just to prevent from making mistakes ... You can have two different accessories for GNSS antennas: 1) a ground plane it prevents the antenna from receiving signals from beneath the antenna (from the ground, roof or whatever is beneath) ... so this could be your pie pan normally 2) a choke ring it creates an area of high impedance around your antenna; because it is just a (set of) simple quarter wave waveguide(s) with short-circuit on one end, you can build it from a sheet of metal by yourself; you only need to calculate the sizes for your waveguide on the L1 frequency ... and if you are a lucky guy and your pie pan fits these sizes, you probably can use it for that ;-) Best regards Martin Is there a design for a choke ring to add to my existing L1 GPS antenna ? Yeah If you are using it for GPSDO work where a ns is good enough and you don't need cm accuracy, It is called a pie pan with its Lip turned up. A choke rings blocks reflected signals from below the antenna from effecting the signals, a pie pan works pretty good at that also. ws *** Hello The Net: Is there a design for a choke ring to add to my existing L1 GPS antenna ? While there may be some variations to the exact dimensions of a choke ring to a specific type of L1 antenna, either patch, helical, etc., I suspect there is some commonality to the design dimensions. I am looking to start construction and I will be using a cheapie patch/puck antenna. Stan, W1LE ___ 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
Re: [time-nuts] Choke Ring Design for L1
Thanks, Nice set of references as always. OK, so its not 100db, But you may of missed my point yet again. If you think I said that a 10 cent pie pan is a good substitute for a $1000 survey antenna in all applications, I think we all know that would be Nonsense. BUT what may not be known is: that a turned up pie pan under my cheap patch/puck antenna, works about as good as an expensive survey antenna for use with a Tbolt GPSDO, That's not Nonsense, It's a tested fact. So I'm not saying there is anything wrong with using a survey antenna on your GPSDO, if you have more money than cents, and you want the last sub ns of performance. But it is not really necessary, there are many many ways to get more bang for the buck, and they would still need to be done first to take advantage of the survey antenna's small improvement when used for a GPSDO. There appears to be a false impression that choke rings remove all Multipath signals. What they do is to remove multipath ground reflected signals from below the antenna, not multipath signals from above it. ws *** Bruce wrote: Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesn't have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf http://www.weblab.dlr.de/rbrt/pdf/TN_0505.pdf http://www.leica-geosystems.com/downloads123/zz/nrs/AR25/brochures/AR25_Brochure_en.pdf Bruce *** WarrenS wrote: > > All true, > BUT > Just to keep from being mislead, > I said what a choke ring antenna does, > You have described how it is so good at its job. > > The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned > thingies, around the antenna is to keep reflected Signals from BELOW > the antenna from sneaking around into the antenna. It does not effect > the signals above the 10 deg or so elevation point. > The choke rings are a necessary to get cm type survey accuracy, > but a pie pan shield /ground plane pretty much does the same thing at > the GPSDO 1ns (1ft) level, > where you don't need 100 db rejection for signals below the antenna. > > What I've found; don't even need to be lucky. > Just put an 8 inch pie pan in the right place, facing the right > direction. > > ws > *** > Hi there, > > just to prevent from making mistakes ... > > You can have two different accessories for GNSS antennas: > 1) a ground plane > it prevents the antenna from receiving signals from beneath the > antenna (from the ground, roof or whatever is beneath) > ... so this could be your pie pan normally > 2) a choke ring > it creates an area of high impedance around your antenna; > because it is just a (set of) simple quarter wave waveguide(s) with > short-circuit on one end, you can build it from a sheet of metal by > yourself; you only need to calculate the sizes for your waveguide on > the L1 frequency ... and if you are a lucky guy and your pie pan > fits > these sizes, you probably can use it for that ;-) > > Best regards > > Martin > > >> Is there a design for a choke ring to add to my existing L1 GPS >> antenna ? > > Yeah > If you are using it for GPSDO work where a ns is good enough and you > don't need cm accuracy, > It is called a pie pan with its Lip turned up. > A choke rings blocks reflected signals from below the antenna from > effecting the signals, a pie pan works pretty good at that also. > ws > > *** >> Hello The Net: > >> Is there a design for a choke ring to add to my existing L1 GPS >> antenna ? >> While there may be some variations to the exact dimensions of a choke >> ring to a specific type of L1 antenna, either patch, helical, etc., >> I suspect there is some commonality to the design dimensions. >> I am looking to start construction and I will be using a cheapie >> patch/puck antenna. > > Stan, W1LE > ___ 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] Choke Ring Design for L1
WarrenS wrote: All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from sneaking around into the antenna. It does not effect the signals above the 10 deg or so elevation point. The choke rings are a necessary to get cm type survey accuracy, but a pie pan shield /ground plane pretty much does the same thing at the GPSDO 1ns (1ft) level, where you don't need 100 db rejection for signals below the antenna. Nonsense, a finite ground plane by itself has little effect on waves incident from underneath, unless of course its a resistive ground plane with just the right surface resistivity. A choke ring antenna doesnt have anything like 100db rejection of multipath signals, the rejection varies with SV elevation. http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html http://www.trimble.com/infrastructure/pdf/gnss-choke-ring-antenna_brochure.pdf http://www.novatel.com/Documents/Papers/3D_choke_ring.pdf http://www.weblab.dlr.de/rbrt/pdf/TN_0505.pdf http://www.leica-geosystems.com/downloads123/zz/nrs/AR25/brochures/AR25_Brochure_en.pdf What I've found; don't even need to be lucky. Just put an 8 inch pie pan in the right place, facing the right direction. ws Bruce *** Hi there, just to prevent from making mistakes ... You can have two different accessories for GNSS antennas: 1) a ground plane it prevents the antenna from receiving signals from beneath the antenna (from the ground, roof or whatever is beneath) ... so this could be your pie pan normally 2) a choke ring it creates an area of high impedance around your antenna; because it is just a (set of) simple quarter wave waveguide(s) with short-circuit on one end, you can build it from a sheet of metal by yourself; you only need to calculate the sizes for your waveguide on the L1 frequency ... and if you are a lucky guy and your pie pan fits these sizes, you probably can use it for that ;-) Best regards Martin Is there a design for a choke ring to add to my existing L1 GPS antenna ? Yeah If you are using it for GPSDO work where a ns is good enough and you don't need cm accuracy, It is called a pie pan with its Lip turned up. A choke rings blocks reflected signals from below the antenna from effecting the signals, a pie pan works pretty good at that also. ws *** Hello The Net: Is there a design for a choke ring to add to my existing L1 GPS antenna ? While there may be some variations to the exact dimensions of a choke ring to a specific type of L1 antenna, either patch, helical, etc., I suspect there is some commonality to the design dimensions. I am looking to start construction and I will be using a cheapie patch/puck antenna. Stan, W1LE ___ 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] Choke Ring Design for L1
For detailed measurements of six different choke ring GPS antennas, see; http://facility.unavco.org/project_support/permanent/equipment/antennas/ant_cals.html John WA4WDL -- From: "WarrenS" Sent: Saturday, March 13, 2010 7:46 PM To: "Discussion of precise time and frequency measurement" Subject: Re: [time-nuts] Choke Ring Design for L1 All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from sneaking around into the antenna. It does not effect the signals above the 10 deg or so elevation point. The choke rings are a necessary to get cm type survey accuracy, but a pie pan shield /ground plane pretty much does the same thing at the GPSDO 1ns (1ft) level, where you don't need 100 db rejection for signals below the antenna. What I've found; don't even need to be lucky. Just put an 8 inch pie pan in the right place, facing the right direction. ws *** Hi there, just to prevent from making mistakes ... You can have two different accessories for GNSS antennas: 1) a ground plane it prevents the antenna from receiving signals from beneath the antenna (from the ground, roof or whatever is beneath) ... so this could be your pie pan normally 2) a choke ring it creates an area of high impedance around your antenna; because it is just a (set of) simple quarter wave waveguide(s) with short-circuit on one end, you can build it from a sheet of metal by yourself; you only need to calculate the sizes for your waveguide on the L1 frequency ... and if you are a lucky guy and your pie pan fits these sizes, you probably can use it for that ;-) Best regards Martin Is there a design for a choke ring to add to my existing L1 GPS antenna ? Yeah If you are using it for GPSDO work where a ns is good enough and you don't need cm accuracy, It is called a pie pan with its Lip turned up. A choke rings blocks reflected signals from below the antenna from effecting the signals, a pie pan works pretty good at that also. ws *** Hello The Net: Is there a design for a choke ring to add to my existing L1 GPS antenna ? While there may be some variations to the exact dimensions of a choke ring to a specific type of L1 antenna, either patch, helical, etc., I suspect there is some commonality to the design dimensions. I am looking to start construction and I will be using a cheapie patch/puck antenna. Stan, W1LE ___ 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] Choke Ring Design for L1
All true, BUT Just to keep from being mislead, I said what a choke ring antenna does, You have described how it is so good at its job. The Main purpose of the choke ring's, hi impedance, 1/4 wave, tuned thingies, around the antenna is to keep reflected Signals from BELOW the antenna from sneaking around into the antenna. It does not effect the signals above the 10 deg or so elevation point. The choke rings are a necessary to get cm type survey accuracy, but a pie pan shield /ground plane pretty much does the same thing at the GPSDO 1ns (1ft) level, where you don't need 100 db rejection for signals below the antenna. What I've found; don't even need to be lucky. Just put an 8 inch pie pan in the right place, facing the right direction. ws *** Hi there, just to prevent from making mistakes ... You can have two different accessories for GNSS antennas: 1) a ground plane it prevents the antenna from receiving signals from beneath the antenna (from the ground, roof or whatever is beneath) ... so this could be your pie pan normally 2) a choke ring it creates an area of high impedance around your antenna; because it is just a (set of) simple quarter wave waveguide(s) with short-circuit on one end, you can build it from a sheet of metal by yourself; you only need to calculate the sizes for your waveguide on the L1 frequency ... and if you are a lucky guy and your pie pan fits these sizes, you probably can use it for that ;-) Best regards Martin Is there a design for a choke ring to add to my existing L1 GPS antenna ? Yeah If you are using it for GPSDO work where a ns is good enough and you don't need cm accuracy, It is called a pie pan with its Lip turned up. A choke rings blocks reflected signals from below the antenna from effecting the signals, a pie pan works pretty good at that also. ws *** Hello The Net: Is there a design for a choke ring to add to my existing L1 GPS antenna ? While there may be some variations to the exact dimensions of a choke ring to a specific type of L1 antenna, either patch, helical, etc., I suspect there is some commonality to the design dimensions. I am looking to start construction and I will be using a cheapie patch/puck antenna. Stan, W1LE ___ 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] Choke Ring Design for L1
Hi there, just to prevent from making mistakes ... You can have two different accessories for GNSS antennas: 1) a ground plane it prevents the antenna from receiving signals from beneath the antenna (from the ground, roof or whatever is beneath) ... so this could be your pie pan normaly 2) a choke ring it creates an area of high impedance around your antenna; because it is just a (set of) simple quarter wave waveguide(s) with short-circuit on one end, you can build it from a sheet of metal by yourself; you only need to calculate the sizes for your waveguide on the L1 frequency ... and if you are a lucky guy and your pie pan fits these sizes, you probably can use it for that ;-) Best regards Martin ___ 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] Choke Ring Design for L1
>Is there a design for a choke ring to add to my existing L1 GPS antenna ? Yeah If you are using it for GPSDO work where a ns is good enough and you don't need cm accuracy, It is called a pie pan with its Lip turned up. A choke rings blocks reflected signals from below the antenna from effecting the signals, a pie pan works pretty good at that also. ws *** > Hello The Net: > Is there a design for a choke ring to add to my existing L1 GPS antenna ? > While there may be some variations to the exact dimensions of a choke > ring to a specific type of L1 antenna, either patch, helical, etc., > I suspect there is some commonality to the design dimensions. > I am looking to start construction and I will be using a cheapie > patch/puck antenna. Stan, W1LE ___ 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] Choke Ring Design for L1
Hi Stan, > Hello The Net: > > Is there a design for a choke ring to add to my existing L1 GPS antenna ? > > While there may be some variations to the exact dimensions of a choke > ring to a specific > type of L1 antenna, either patch, helical, etc., > I suspect there is some commonality to the design dimensions. > > I am looking to start construction and I will be using a cheapie > patch/puck antenna. > > Stan, W1LE Here might be a good start for you. http://www.febo.com/pipermail/time-nuts/2008-January/029277.html -- Björn ___ 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] Choke Ring Design for L1
Hello The Net: Is there a design for a choke ring to add to my existing L1 GPS antenna ? While there may be some variations to the exact dimensions of a choke ring to a specific type of L1 antenna, either patch, helical, etc., I suspect there is some commonality to the design dimensions. I am looking to start construction and I will be using a cheapie patch/puck antenna. Stan, W1LE ___ 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.
