Re: [time-nuts] antennas was Re: Common-View GPS Network
If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. I can see now why surveyers need the choke ring type antenna, because they can not choose the location. They need to place it where they need to measure. But timing is different, we can choose the best location which would be two meters above the tallest object in the area. The cake pan certainly would work. This is not super critical. They are only blocking low elevation signals. and it would give you more option for the location On Wed, Apr 17, 2013 at 8:14 PM, Jim Lux jim...@earthlink.net wrote: Javad has a bunch of choke ring theory.. http://www.javad.com/jns/**index.html?/jns/technology/** Single-Depth%20Low-Multipath%**20Choke%20Ring.htmlhttp://www.javad.com/jns/index.html?/jns/technology/Single-Depth%20Low-Multipath%20Choke%20Ring.html http://www.javad.com/jns/**index.html?/jns/technology/** Choke%20Ring%20Theory.htmlhttp://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html Their conclusion is you want the depth of the ring to be slightly more than 1/4 lambda. lambda/4 for L1 is 1.87 so a 2 cake pan is just about the right size. -- 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.
Re: [time-nuts] antennas was Re: Common-View GPS Network
On 4/18/13 12:01 AM, Chris Albertson wrote: If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. yes.. multipath that is more than a chip away is generally filtered out by the PN tracking loop, so all you really worry about is multipath signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300 meters long. If you're doing P/Y code, it's a tenth of that. In reality, if the multipath signal is lower, and it's far away (a good fraction of a chip) it doesn't contribute much to the output of the correlator. So their 10 meter thing is probably a good number for a typical receiver they make. ___ 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] antennas was Re: Common-View GPS Network
On 04/18/2013 04:00 PM, Jim Lux wrote: On 4/18/13 12:01 AM, Chris Albertson wrote: If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. yes.. multipath that is more than a chip away is generally filtered out by the PN tracking loop, so all you really worry about is multipath signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300 meters long. If you're doing P/Y code, it's a tenth of that. In reality, if the multipath signal is lower, and it's far away (a good fraction of a chip) it doesn't contribute much to the output of the correlator. So their 10 meter thing is probably a good number for a typical receiver they make. It's an interesting mix of sample-rate/bandwidth, code you track and distance between early-late detectors (normal distance is one chip) comes in when analyzing and combat the multi-path. I recall there is some subtle points with some of the C/A codes. 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] antennas was Re: Common-View GPS Network
I hope I am not steering the thread to much, I have an Allen Osborne TurboRogue SMR12 RM L1 L2 GPS rec that came from JPL that appears specifically designed for Common View use. Does anyone know the history of these ,I can find almost nothing. Email me directly if you have info, or I can start a new thread. Tom Knox act...@hotmail.com Date: Thu, 18 Apr 2013 19:58:22 +0200 From: mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] antennas was Re: Common-View GPS Network On 04/18/2013 04:00 PM, Jim Lux wrote: On 4/18/13 12:01 AM, Chris Albertson wrote: If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. yes.. multipath that is more than a chip away is generally filtered out by the PN tracking loop, so all you really worry about is multipath signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300 meters long. If you're doing P/Y code, it's a tenth of that. In reality, if the multipath signal is lower, and it's far away (a good fraction of a chip) it doesn't contribute much to the output of the correlator. So their 10 meter thing is probably a good number for a typical receiver they make. It's an interesting mix of sample-rate/bandwidth, code you track and distance between early-late detectors (normal distance is one chip) comes in when analyzing and combat the multi-path. I recall there is some subtle points with some of the C/A codes. 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] antennas was Re: Common-View GPS Network
Tom, Let's do a separate thread on that one. Cheers, Magnus On 04/18/2013 08:07 PM, Tom Knox wrote: I hope I am not steering the thread to much, I have an Allen Osborne TurboRogue SMR12 RM L1 L2 GPS rec that came from JPL that appears specifically designed for Common View use. Does anyone know the history of these ,I can find almost nothing. Email me directly if you have info, or I can start a new thread. Tom Knox act...@hotmail.com Date: Thu, 18 Apr 2013 19:58:22 +0200 From: mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] antennas was Re: Common-View GPS Network On 04/18/2013 04:00 PM, Jim Lux wrote: On 4/18/13 12:01 AM, Chris Albertson wrote: If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. yes.. multipath that is more than a chip away is generally filtered out by the PN tracking loop, so all you really worry about is multipath signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300 meters long. If you're doing P/Y code, it's a tenth of that. In reality, if the multipath signal is lower, and it's far away (a good fraction of a chip) it doesn't contribute much to the output of the correlator. So their 10 meter thing is probably a good number for a typical receiver they make. It's an interesting mix of sample-rate/bandwidth, code you track and distance between early-late detectors (normal distance is one chip) comes in when analyzing and combat the multi-path. I recall there is some subtle points with some of the C/A codes. 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. ___ 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] antennas was Re: Common-View GPS Network
Magnus, Jim, On 04/18/2013 04:00 PM, Jim Lux wrote: On 4/18/13 12:01 AM, Chris Albertson wrote: If I read the paper correctly you can skip the choke ring if you mount the antenna on top of a 2 meter or longer mast. Iron pipe comes on 10 foot lengths. The choke ring is for portable survey antenna that can't be placed on tall rooftop masts. I think a 2 meter pole on a roof pretty much meets their criteria of multi path difference being over 10 meters. yes.. multipath that is more than a chip away is generally filtered out by the PN tracking loop, so all you really worry about is multipath signals within a chip. For C/A code at 1 Mchip/sec, the chips are 300 meters long. If you're doing P/Y code, it's a tenth of that. In reality, if the multipath signal is lower, and it's far away (a good fraction of a chip) it doesn't contribute much to the output of the correlator. So their 10 meter thing is probably a good number for a typical receiver they make. It's an interesting mix of sample-rate/bandwidth, code you track and distance between early-late detectors (normal distance is one chip) comes in when analyzing and combat the multi-path. I recall there is some subtle points with some of the C/A codes. All of the high quality GNSS receiver manufacturers have their own version of correlator that try to mitigate multipath. See for example this Ashtech-document (for a ca 10 year old L1 only receiver (DG14/16)). ftp://ftp.ashtech.com/OEM,%20Sensor%20%20ADU/DG16%20%20DG14/Reference%20Material/Correlator.doc /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.
Re: [time-nuts] antennas was Re: Common-View GPS Network
On 4/18/13 1:40 PM, b...@lysator.liu.se wrote: All of the high quality GNSS receiver manufacturers have their own version of correlator that try to mitigate multipath. See for example this Ashtech-document (for a ca 10 year old L1 only receiver (DG14/16)). ftp://ftp.ashtech.com/OEM,%20Sensor%20%20ADU/DG16%20%20DG14/Reference%20Material/Correlator.doc I'm sure.. I wonder, though, if you have a GPS receiver for which you do not know how it works internally, can one come up with a guideline for how much multipath suppression you want. At some level, all those fancy algorithms are trying to build an adaptive equalizer and/or filter for the multipath, helped by the knowledge that the true path is the shortest one. In theory, one should be able to deconvolve arbitrary multipath (if you collect all signals from all directions of the sky, etc.), but I think the idea of the chokering (and other clever antenna designs) is to reduce the work for the back end processing. ___ 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] antennas was Re: Common-View GPS Network
Another way to ask this question is what is the effect of a small deviation form the ideal dimensions? If we assume deviations of about 1/20th of a wavelength are OK then we can allow about 1cm of dimensional error. Almost anyone using simple hand tools can do better. With care using primitive garage equipment we can do much better. The old-school hand method for precision sheet metal work was to make a hardwood form and then bend and cut the metal around the wood form. I think if a cake pan would work is a matter of luck. You'd just have to find one within about 2cm of the correct diameter. If not then you be better off starting with flat sheet and hand shears. On Tue, Apr 16, 2013 at 10:46 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: From: Sarah White I just have to ask though... cake pans? really? I can't imagine it would even be possible to modify a cake pan with enough accuracy to get a usable antenna. -- 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.
Re: [time-nuts] antennas was Re: Common-View GPS Network
But the pan is just a ground plane. It isn't a reflector based on the type of antennas I saw in the photograph. Sent via BlackBerry from T-Mobile -Original Message- From: Chris Albertson albertson.ch...@gmail.com Sender: time-nuts-boun...@febo.com Date: Wed, 17 Apr 2013 12:18:00 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] antennas was Re: Common-View GPS Network Another way to ask this question is what is the effect of a small deviation form the ideal dimensions? If we assume deviations of about 1/20th of a wavelength are OK then we can allow about 1cm of dimensional error. Almost anyone using simple hand tools can do better. With care using primitive garage equipment we can do much better. The old-school hand method for precision sheet metal work was to make a hardwood form and then bend and cut the metal around the wood form. I think if a cake pan would work is a matter of luck. You'd just have to find one within about 2cm of the correct diameter. If not then you be better off starting with flat sheet and hand shears. On Tue, Apr 16, 2013 at 10:46 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: From: Sarah White I just have to ask though... cake pans? really? I can't imagine it would even be possible to modify a cake pan with enough accuracy to get a usable antenna. -- 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. ___ 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] antennas was Re: Common-View GPS Network
On 4/17/13 12:18 PM, Chris Albertson wrote: Another way to ask this question is what is the effect of a small deviation form the ideal dimensions? If we assume deviations of about 1/20th of a wavelength are OK then we can allow about 1cm of dimensional error. Almost anyone using simple hand tools can do better. With care using primitive garage equipment we can do much better. The old-school hand method for precision sheet metal work was to make a hardwood form and then bend and cut the metal around the wood form. I think if a cake pan would work is a matter of luck. You'd just have to find one within about 2cm of the correct diameter. If not then you be better off starting with flat sheet and hand shears. since you can buy cake pans in even inch increments, I think the cake pan will work.. BTW, I've been looking at some choke rings with only 2 rings instead of the usual 3. Apparently, the performance isn't all that much different. When I asked why do all the other ones have 3, it boils down to the first one had 3 and everyone just copied it. Javad has a bunch of choke ring theory.. http://www.javad.com/jns/index.html?/jns/technology/Single-Depth%20Low-Multipath%20Choke%20Ring.html http://www.javad.com/jns/index.html?/jns/technology/Choke%20Ring%20Theory.html Their conclusion is you want the depth of the ring to be slightly more than 1/4 lambda. lambda/4 for L1 is 1.87 so a 2 cake pan is just about the right size. ___ 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] antennas was Re: Common-View GPS Network
From: li...@lazygranch.com But the pan is just a ground plane. It isn't a reflector based on the type of antennas I saw in the photograph. = If you are referring to my antenna farm photo, that's correct. It is also magnetic, so it holds the pucks in place. 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] antennas was Re: Common-View GPS Network
On 4/16/2013 1:55 AM, Jim Lux wrote: On 4/15/13 10:22 PM, Jim Lux wrote: On 4/15/13 9:27 PM, Tom Van Baak wrote: NIST SIM GPS common view pinwheel described in one of the NIST reports as an aperture coupled slot fed array that is better than a patch, but not as large and heavy as a choke ring. W. Kunysz, 2000, “High Performance GPS Pinwheel Antenna,” in Proceedings of the 2000 International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GPS 2000), 19-22 September 2000, Salt Lake City, Utah, USA (ION, Alexandria, Virginia), pp. 2506-251 http://www.novatel.com/assets/Documents/Papers/GPS-704xWhitePaper.pdf Patented by Novatel Pinwheel is a trademark Performance is almost as good as a choke ring but a heck of a lot smaller and lighter. of course, cake pans with 2-2.5 inch high walls are readily available. There's a Wilton cakepan set with 6,8 and 10 diameter pans with 3 walls.. hmm, an inch between fins.. Oddly, the package shipping size is 12x12x2... I wonder how they fit a 3 high pan in a 2 thick box.. a real restaurant/pastry supply has a mindboggling variety of pans http://www.fantes.com/cake-pans-round.html every integer inch diameter from 4 to 18 and ditto for heights from 2 to 4... People like those machined or cast choke rings because they're easier to fabricate: Slap a block of aluminum in the lathe or milling machine, push GO on the CNC, and stand back. Or for those with a taste for hot metal.. you could cast it with scrap aluminum you've melted in the forge in your time nuts lab.. Turn those empty beer cans into something useful. If you have a fancy multiaxis mill, you could probably do one of those porcupine looking things. Or, if you have a swimming pool or pond, and some sheet aluminum, and some suitable high explosives.. hydroforming is your friend. If you want true timenuts.. do the explosive hydroforming without a mold/buck, and instead use precision timing of shaped charges. Finally, a use for those krytron switches you found at the surplus place. Thanks for that. The last bit of your post was really cute. I needed a good laugh :) I haven't posted much in a while, partly because I've been kinda bummed out by this list since I got the news about shera... There have been so many constant reminders of his passing and whatnot (multiple thread titles mentioning his legacy) I just have to ask though... cake pans? really? I can't imagine it would even be possible to modify a cake pan with enough accuracy to get a usable antenna. -- Sarah ___ 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] antennas was Re: Common-View GPS Network
On 4/16/13 5:19 PM, Sarah White wrote: I just have to ask though... cake pans? really? I can't imagine it would even be possible to modify a cake pan with enough accuracy to get a usable antenna. Sure.. cake pans, like other stamped goods, are actually pretty high precision, because they're all stamped out of the same die. As long as the dimensions are right (and for choke rings that's not real critical), it works. ___ 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] antennas was Re: Common-View GPS Network
From: Sarah White I just have to ask though... cake pans? really? I can't imagine it would even be possible to modify a cake pan with enough accuracy to get a usable antenna. -- Sarah Well, my GPS antenna farm uses an inverted baking tray http://www.satsignal.eu/ntp/2013-03-31-1226-32-GPS-antenna-farm.jpg 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.
[time-nuts] antennas was Re: Common-View GPS Network
On 4/15/13 10:22 PM, Jim Lux wrote: On 4/15/13 9:27 PM, Tom Van Baak wrote: NIST SIM GPS common view pinwheel described in one of the NIST reports as an aperture coupled slot fed array that is better than a patch, but not as large and heavy as a choke ring. W. Kunysz, 2000, “High Performance GPS Pinwheel Antenna,” in Proceedings of the 2000 International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GPS 2000), 19-22 September 2000, Salt Lake City, Utah, USA (ION, Alexandria, Virginia), pp. 2506-251 http://www.novatel.com/assets/Documents/Papers/GPS-704xWhitePaper.pdf Patented by Novatel Pinwheel is a trademark Performance is almost as good as a choke ring but a heck of a lot smaller and lighter. of course, cake pans with 2-2.5 inch high walls are readily available. There's a Wilton cakepan set with 6,8 and 10 diameter pans with 3 walls.. hmm, an inch between fins.. Oddly, the package shipping size is 12x12x2... I wonder how they fit a 3 high pan in a 2 thick box.. a real restaurant/pastry supply has a mindboggling variety of pans http://www.fantes.com/cake-pans-round.html every integer inch diameter from 4 to 18 and ditto for heights from 2 to 4... People like those machined or cast choke rings because they're easier to fabricate: Slap a block of aluminum in the lathe or milling machine, push GO on the CNC, and stand back. Or for those with a taste for hot metal.. you could cast it with scrap aluminum you've melted in the forge in your time nuts lab.. Turn those empty beer cans into something useful. If you have a fancy multiaxis mill, you could probably do one of those porcupine looking things. Or, if you have a swimming pool or pond, and some sheet aluminum, and some suitable high explosives.. hydroforming is your friend. If you want true timenuts.. do the explosive hydroforming without a mold/buck, and instead use precision timing of shaped charges. Finally, a use for those krytron switches you found at the surplus place. ___ 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.
