Re: [time-nuts] Cable delay correction for Tbolt Cs substitude
On 10/17/2011 02:28 AM, Mark Sims wrote: Yes, at one time there was some very precision surveying antennas that were temperature controlled. I'm not sure if they were just controlling just the preamp or the whole antenna, but I got the impression that they were controlling the temperature everything inside the radome package. At one time I did some TDR measurements on a piece of coax (I think it was 100 feet of black RG59). The day/night prop time variation was under a nanosecond. Something tells me that the cable delay changes itself won't make any difference. - Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. I know that SP in Borås have actually temperature-controlled also their cable. Not only the pillar and radome. 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] Cable delay correction for Tbolt Cs substitude
Anyone know what the propagation delay temperature coefficient is for RG6U coax and how much it varies between different brands of cable? In my efforts to improve the Tbolt's performance to make it into a better Cs substitute, test suggest that the temperature coefficient of the antenna lead-in cable's propagation delay is contributing to diurnal errors. Anyone have a idea for a SIMPLE cheap voltage controlled delay line that can be changed by a few ns as a function of the outside air temperature? As an alternative, Mark, want to consider adding another LadyHeather feature that tweaks the Tbolt's cable delay value as a function of the outside temperature? If interested, I have a couple ideas of how to get the outside temperature to LadyHeather. 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] Cable delay correction for Tbolt Cs substitude
Using the cable delay message is probably not a good idea... it resets the internal filters and state every time you change it. ___ 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] Cable delay correction for Tbolt Cs substitude
Thanks John Any chance using 75 ohm cable (as suggested in the Tbolt manual) like RG6U, when used in a 50 Ohm system could be orders of magnitude worse than LMR-400? Sounds like may be time to do some controlled cable experiments comparing different cables. I do know that Cheapie GPS timing antenna's can have a large Phase variation when the Sun hits them. I had one antenna that changed 25 ns every day around Noon time. That is when I changed over to a Symmetricom 58532A antenna and things improved 10 fold. With the new antenna the phase error change is now down at least near the GPS noise level, but it seems to still have some antenna system temperature effects. Maybe a silly question but how can a 1.5GHz preamp and filter change the phase over so many cycles? Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ws ** from John Ackermann N8UR I did some very rough measurements last summer with. Run of LMR-400 that was laying on the roof in the hot Georgia sun. Using a network analyzer to ping the cable I found the day vs. night delay difference was pretty much in the noise. I'll see if I can find the details and if so will post them. I found via google a brief paper from Haystack that measured LMR-400 and LMR-240 and found in the range of -11 to +17 ppm/K of the total cable delay. They note that 9 ppm/K is about 3ps/degree in 100M of cable: http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/069.pdf However, there's another possible tempo contributor that I suspect could be a significant contributor, and that's the preamp up in the antenna, particularly if it has a bandpass filter. It wouldn't surprise me at all if preamp/BPF tempo was noticeable. John On Oct 16, 2011, at 1:32 PM, WarrenS wrote: Anyone know what the propagation delay temperature coefficient is for RG6U coax and how much it varies between different brands of cable? In my efforts to improve the Tbolt's performance to make it into a better Cs substitute, test suggest that the temperature coefficient of the antenna lead-in cable's propagation delay is contributing to diurnal errors. Anyone have a idea for a SIMPLE cheap voltage controlled delay line that can be changed by a few ns as a function of the outside air temperature? As an alternative, Mark, want to consider adding another LadyHeather feature that tweaks the Tbolt's cable delay value as a function of the outside temperature? If interested, I have a couple ideas of how to get the outside temperature to LadyHeather. 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] Cable delay correction for Tbolt Cs substitude
I wouldn't think the cable type will make an order-of-magnitude difference. Referenced in the Haystack note is another paper that goes through the theoretical derivation that produced the expected results column. I think it's the same URL but 067.pdf as the file name. John On Oct 16, 2011, at 2:21 PM, WarrenS warrensjmail-...@yahoo.com wrote: Thanks John Any chance using 75 ohm cable (as suggested in the Tbolt manual) like RG6U, when used in a 50 Ohm system could be orders of magnitude worse than LMR-400? Sounds like may be time to do some controlled cable experiments comparing different cables. I do know that Cheapie GPS timing antenna's can have a large Phase variation when the Sun hits them. I had one antenna that changed 25 ns every day around Noon time. That is when I changed over to a Symmetricom 58532A antenna and things improved 10 fold. With the new antenna the phase error change is now down at least near the GPS noise level, but it seems to still have some antenna system temperature effects. Maybe a silly question but how can a 1.5GHz preamp and filter change the phase over so many cycles? Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ws ** from John Ackermann N8UR I did some very rough measurements last summer with. Run of LMR-400 that was laying on the roof in the hot Georgia sun. Using a network analyzer to ping the cable I found the day vs. night delay difference was pretty much in the noise. I'll see if I can find the details and if so will post them. I found via google a brief paper from Haystack that measured LMR-400 and LMR-240 and found in the range of -11 to +17 ppm/K of the total cable delay. They note that 9 ppm/K is about 3ps/degree in 100M of cable: http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/069.pdf However, there's another possible tempo contributor that I suspect could be a significant contributor, and that's the preamp up in the antenna, particularly if it has a bandpass filter. It wouldn't surprise me at all if preamp/BPF tempo was noticeable. John On Oct 16, 2011, at 1:32 PM, WarrenS wrote: Anyone know what the propagation delay temperature coefficient is for RG6U coax and how much it varies between different brands of cable? In my efforts to improve the Tbolt's performance to make it into a better Cs substitute, test suggest that the temperature coefficient of the antenna lead-in cable's propagation delay is contributing to diurnal errors. Anyone have a idea for a SIMPLE cheap voltage controlled delay line that can be changed by a few ns as a function of the outside air temperature? As an alternative, Mark, want to consider adding another LadyHeather feature that tweaks the Tbolt's cable delay value as a function of the outside temperature? If interested, I have a couple ideas of how to get the outside temperature to LadyHeather. 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] Cable delay correction for Tbolt Cs substitude
Its merely a calculation of the change in inductance due to the temperature induced change in skin depth due to the resistivity tempco of the inner conductor wich varies the inductance per unit length. Since RG6 uses a copper plated steel inner conductor there may be significant differences in the inductance tempco should the plating thickness not be much greater than the skin depth (most likely at lower frequencies). The thermal expansion of the inner conductor will also be smaller than that of a copper conductor. Thus the delay tempco of RG6 may differ somewhat from that of LMR400. Bruce John Ackermann N8UR wrote: I wouldn't think the cable type will make an order-of-magnitude difference. Referenced in the Haystack note is another paper that goes through the theoretical derivation that produced the expected results column. I think it's the same URL but 067.pdf as the file name. John On Oct 16, 2011, at 2:21 PM, WarrenSwarrensjmail-...@yahoo.com wrote: Thanks John Any chance using 75 ohm cable (as suggested in the Tbolt manual) like RG6U, when used in a 50 Ohm system could be orders of magnitude worse than LMR-400? Sounds like may be time to do some controlled cable experiments comparing different cables. I do know that Cheapie GPS timing antenna's can have a large Phase variation when the Sun hits them. I had one antenna that changed 25 ns every day around Noon time. That is when I changed over to a Symmetricom 58532A antenna and things improved 10 fold. With the new antenna the phase error change is now down at least near the GPS noise level, but it seems to still have some antenna system temperature effects. Maybe a silly question but how can a 1.5GHz preamp and filter change the phase over so many cycles? Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ws ** from John Ackermann N8UR I did some very rough measurements last summer with. Run of LMR-400 that was laying on the roof in the hot Georgia sun. Using a network analyzer to ping the cable I found the day vs. night delay difference was pretty much in the noise. I'll see if I can find the details and if so will post them. I found via google a brief paper from Haystack that measured LMR-400 and LMR-240 and found in the range of -11 to +17 ppm/K of the total cable delay. They note that 9 ppm/K is about 3ps/degree in 100M of cable: http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/069.pdf However, there's another possible tempo contributor that I suspect could be a significant contributor, and that's the preamp up in the antenna, particularly if it has a bandpass filter. It wouldn't surprise me at all if preamp/BPF tempo was noticeable. John On Oct 16, 2011, at 1:32 PM, WarrenS wrote: Anyone know what the propagation delay temperature coefficient is for RG6U coax and how much it varies between different brands of cable? In my efforts to improve the Tbolt's performance to make it into a better Cs substitute, test suggest that the temperature coefficient of the antenna lead-in cable's propagation delay is contributing to diurnal errors. Anyone have a idea for a SIMPLE cheap voltage controlled delay line that can be changed by a few ns as a function of the outside air temperature? As an alternative, Mark, want to consider adding another LadyHeather feature that tweaks the Tbolt's cable delay value as a function of the outside temperature? If interested, I have a couple ideas of how to get the outside temperature to LadyHeather. 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. ___ 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] Cable delay correction for Tbolt Cs substitude
Sounds like its time to do some testing and see what the effect is on the actual hardware. 1) Heat and cool the Tbolt box and see if that effects THIS Phase delay, maybe by way of its internal GPS amp/BPF. In the past I have not seen a need to use LH's temperature controller on a Tbolt that is driving an external Dual oven Osc or a temperature stabilized Rb like this Tbolt is. 2) Place an extra 50 ft of RG6 between the Antenna and the Tbolt inside an oven, then heat and cool it. 3) Put the Roof top antenna in an RF transparent box with a heater. too much fun ws Griffiths bruce.griffiths at xtra.co.nz wrote: It's merely a calculation of the change in inductance due to the temperature induced change in skin depth due to the resistivity tempco of the inner conductor which varies the inductance per unit length. Since RG6 uses a copper plated steel inner conductor there may be significant differences in the inductance tempco should the plating thickness not be much greater than the skin depth (most likely at lower frequencies). The thermal expansion of the inner conductor will also be smaller than that of a copper conductor. Thus the delay tempco of RG6 may differ somewhat from that of LMR400. Bruce *** John Ackermann N8UR wrote: I wouldn't think the cable type will make an order-of-magnitude difference. Referenced in the Haystack note is another paper that goes through the theoretical derivation that produced the expected results column. I think it's the same URL but 067.pdf as the file name. John On Oct 16, 2011, at 2:21 PM, WarrenS wrote: Thanks John Any chance using 75 ohm cable (as suggested in the Tbolt manual) like RG6U, when used in a 50 Ohm system could be orders of magnitude worse than LMR-400? Sounds like may be time to do some controlled cable experiments comparing different cables. I do know that Cheapie GPS timing antenna's can have a large Phase variation when the Sun hits them. I had one antenna that changed 25 ns every day around Noon time. That is when I changed over to a Symmetricom 58532A antenna and things improved 10 fold. With the new antenna the phase error change is now down at least near the GPS noise level, but it seems to still have some antenna system temperature effects. Maybe a silly question but how can a 1.5GHz preamp and filter change the phase over so many cycles? Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ws ** from John Ackermann N8UR I did some very rough measurements last summer with. Run of LMR-400 that was laying on the roof in the hot Georgia sun. Using a network analyzer to ping the cable I found the day vs. night delay difference was pretty much in the noise. I'll see if I can find the details and if so will post them. I found via google a brief paper from Haystack that measured LMR-400 and LMR-240 and found in the range of -11 to +17 ppm/K of the total cable delay. They note that 9 ppm/K is about 3ps/degree in 100M of cable: http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/069.pdf However, there's another possible tempo contributor that I suspect could be a significant contributor, and that's the preamp up in the antenna, particularly if it has a bandpass filter. It wouldn't surprise me at all if preamp/BPF tempo was noticeable. John On Oct 16, 2011, at 1:32 PM, WarrenS wrote: Anyone know what the propagation delay temperature coefficient is for RG6U coax and how much it varies between different brands of cable? In my efforts to improve the Tbolt's performance to make it into a better Cs substitute, test suggest that the temperature coefficient of the antenna lead-in cable's propagation delay is contributing to diurnal errors. Anyone have a idea for a SIMPLE cheap voltage controlled delay line that can be changed by a few ns as a function of the outside air temperature? As an alternative, Mark, want to consider adding another LadyHeather feature that tweaks the Tbolt's cable delay value as a function of the outside temperature? If interested, I have a couple ideas of how to get the outside temperature to LadyHeather. 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] Cable delay correction for Tbolt Cs substitude
Yes, at one time there was some very precision surveying antennas that were temperature controlled. I'm not sure if they were just controlling just the preamp or the whole antenna, but I got the impression that they were controlling the temperature everything inside the radome package. At one time I did some TDR measurements on a piece of coax (I think it was 100 feet of black RG59). The day/night prop time variation was under a nanosecond. Something tells me that the cable delay changes itself won't make any difference. - Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ___ 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] Cable delay correction for Tbolt Cs substitude
Mark, Warren, That's correct. Some dual-frequency geodetic-grade GPS receivers use thermally stabilized antennas. It's one more trick in the quest for nanosecond stability and there's no reason one couldn't homebrew one. There are photos of them on the web. It would also not be hard to test, especially if you use a TEC so you can manually set the temperature way up and down over fractions to multiples of an hour. Or compare it in real time against an unstabilized sister antenna and TBolt. Good reading, performance charts graphs: http://www.ngs.noaa.gov/CORS/Articles/metrologia-2.pdf Geodetic techniques for time and frequency comparisons using GPS phase and code measurements More info at CORS and IGS sites: http://www.ngs.noaa.gov/CORS/ http://igscb.jpl.nasa.gov/ I agree on your cable comments. I used Andrew Heliax on my L1/L2 antenna back when I was running a Z-12T. At its best it was good to cm levels, way below 1 ns. http://leapsecond.com/pages/quake/panga-tvb1.gif Would it be possible to run a controlled current down the coax to maintain constant temperature 24x7? You could use its resistance as a proxy for temperature. /tvb - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Sunday, October 16, 2011 5:28 PM Subject: [time-nuts] Cable delay correction for Tbolt Cs substitude Yes, at one time there was some very precision surveying antennas that were temperature controlled. I'm not sure if they were just controlling just the preamp or the whole antenna, but I got the impression that they were controlling the temperature everything inside the radome package. At one time I did some TDR measurements on a piece of coax (I think it was 100 feet of black RG59). The day/night prop time variation was under a nanosecond. Something tells me that the cable delay changes itself won't make any difference. - Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. ___ 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] Cable delay correction for Tbolt Cs substitude
On 16 Oct, 2011, at 11:21 , WarrenS wrote: Does anyone ever add a temperature controller on the antenna? Maybe that should be my next test. I've seen commercial temperature-controlled antennas. Here's one: http://adriang.com/AACE-Industries/products.htm Dennis Ferguson ___ 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.
