Re: [time-nuts] Bls: time-nuts Digest, Vol 130, Issue 38
Hi What is your goal? Do you want something that works as well as a $125 eBay GPSDO? What is your end application? Do you have a cheap source of 100 Hz wide 10 MHz crystal filters? The main problem with a simple approach like the one you propose is that the filter is probably to wide at 100 Hz and at the same time to narrow to source cheaply. Your PLL loop filter will need to be in the 1/100 to 1/1000 Hz range to work “as well as” the eBay part. The as received GPS signal has a *lot* of noise on it. How do you plan to implement this filter? Normally digital filtering is used. Once you go digital, a 1 pps lock frequency is a easy thing to do. Lots of choices. Bob On May 26, 2015, at 12:58 PM, Anton Moehammad via time-nuts time-nuts@febo.com wrote: Dear All This is the first time I posted in this forum so please forgive me if its already discuss before I like to ask You who has more experience about my plan for USD75 GPSDO before I explain my plan let me tell You some real world limitation 1. The parts I choose must be available in local store (custom bussiness cost a lot of time) 2. I do not aim for something special a magnitude better than my MTI milliren OCXO is welcome. Now What in my mind I will use Ublox 7m GPS board that can program from 0,25Mhz to 10Mhz (https://sites.google.com/site/g4zfqradio/u-blox_neo-6-7) But the problem are I found someone (http://www.ra3apw.ru/proekty/ublox-neo-7m/) already do the spectrum analysis for this board and the result is like this : and the last picture is far better, correct ? so what I need to do I have 2 plan : 1. use the board 10Mhz output than use very narrow (100Hz bandwith) Crystal filter 2. Use the 4Mhz output than again filter it use Crystal filter to clean it than use it as reference for PLL for controling 10Mhz OCXO Which one you think a better way. last I also like to know because MTI only spec the OCXO model 240 harmonics to down to -30dB (http://www.mti-milliren.com/pdfs/240.pdf) is there any benefit to use a crystal filter in the output to clearer it more. any opinion is very welcome Thank You Anton Pada Selasa, 26 Mei 2015 23:00, time-nuts-requ...@febo.com time-nuts-requ...@febo.com menulis: Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Terrestrial Tides and Land Movement (Bob Camp) 2. Re: Terrestrial Tides and Land Movement (Bob Stewart) 3. pp2s? No, 1pps from a Nortel GPSTM! (Nathaniel Bezanson) 4. Re: FTS 8400 (Gregory Beat) 5. Re: 3048A software question (davidh) 6. Re: LTC6957 internal architecture (David C. Partridge) 7. Re: pp2s? No, 1pps from a Nortel GPSTM! (Tom Van Baak) 8. Re: 3048A software question (Chuck Harris) 9. Re: Terrestrial Tides and Land Movement (Chuck Harris) 10. Re: TymServe 2100 1995 Issue - A Kludgy Fix (Esa Heikkinen) -- Message: 1 Date: Mon, 25 May 2015 19:01:02 -0400 From: Bob Camp kb...@n1k.org To: Bob Stewart b...@evoria.net, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Message-ID: c83d4da8-3e3d-462f-abff-3dae1f645...@n1k.org Content-Type: text/plain; charset=utf-8 Hi Let’s step back a bit: Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere. One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight path today. A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS and the like to improve things. A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to an LEA-8T (or similar). More sats is going to give you a better position solution. The bottom
Re: [time-nuts] 3048A software question
David, the 82335 drivers came with the complete SW package that I sent you. I don't know if the drivers and SW are running with any more recent or non MS versions than MS-DOS 6.0. But, it's as easy to find out as it gets. Back in the day the whole OS fitted on a floppy disk and 640k of memory, together with a 33 MHz 486 did the job. Btw. a modern 2,000 MHz or something clocked PC with 4,000,000k of memory doesn't seem to work any faster... And, no, even if you get MS-DOS installed on it, you're not gonna have much fun. Adrian davidh schrieb: Folks, I'm also working on getting the MSDOS version running. What is the most recent version of DOS that people have found to work with the A 01.01 version. Also, can anyone advise where the command drivers for the 82335 can be found? Cheers, david Hi Adrian, Got the spec lines working now, thanks! Yes, the DOS version. I was hoping for an updated user manual for that version as the manual describes the other software version, and maybe a slightly later sw version. Oh well. Thanks for you help! Said On Feb 17, 2012, at 5:06, Adrian rfnuts-kvp5wt2u...@public.gmane.org wrote: Said, are you using the Opt. 311 (MS-DOS) software? I don't know of any more recent versions. To answer your initial question: You can not change anything on the diagram _after_ the measurement, not even the title. The spec lines will be visible only when you have defined them prior to starting the measurement. Regards, Adrian saidjack-ydxpq3io...@public.gmane.org schrieb: Hello team, I am trying to get an HP 3048A system up and running, and I am having problems with enabling spec limit lines on the graph. I can enter the spec line data under the manipulate results then spec lines menu, but the lines I entered are not visible. There are the standard spec lines visible when I do the internal noise floor test, so I know this should work. Does anyone know how to enable these properly? The user manual doesn't talk about this, and it is written for an older version of the software anyway's. Also, I have software version A 01.01 from 1994, does anyone have any more recent software version? Thanks in advance, Said ___ time-nuts mailing list -- time-nuts-jsktletq...@public.gmane.org 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-jsktletq...@public.gmane.org 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.
[time-nuts] Navman T60-D125 GPS Timing Receiver Problems
Many of the Navman T60-D125 units are floating around on various sales sites. Unfortunately, some come with built in problems and poor documentation. Here are some things that I have found in working with one for the past year. 1) If you have found that communicating with the unit on the development board over the RS232 serial port is impossible, here is why: there is a flaw on the development board. When I bought my board, there was no communication to the unit. I thought the serial chip was bad and went to replace it. I discovered there is a serious flaw on the board. TX1 IN (PIN 11) is connected to TX2 OUT (PIN 7). It appears it should be connected to the pin opposite to it (PIN 10) which is TX2 IN. I removed the SP232 chip and cut the trace to Pin 7 (TX2OUT) under the SP232. Now the unit functions OK. 2) Some documentation mentions that the TU60-D120 (note 120 not 125 - there is no docs on the 125 out there) series is supposed to default to survey mode followed by position hold (best for time measurements). This does not occur with the unit I bought - a TU60-D125. You must put the unit into binary communication mode (@@Wb command at 9600 8N1) and then use 1255 command to set it to survey mode and then onto position hold. You use this command to configure the unit as a TRAIM receiver. (By the way, when you use the @@Wb command to switch serial protocols, it will immediately start spitting out data. Look for the 1056 message and it will tell you what mode the unit is in - and that survey mode on power up is DISABLED!!) 3) If you configure the unit with the 1255 command, it will NOT remember this configuration after power cycle - despite the function of the 1255 command is supposed to do this. So you need to do this each time you power up. That is, it will start out in the mode where it only responds to the @@XX commands and you must use @@Wb to switch over to the binary mode. And the use the 1255 command to command it into survey mode. After 24hrs (or what ever time you choose) it will transition to position hold and work to specs. I am comparing the output with a homebrew (yes, I mean it) WWVB receiver and getting delta F's comparing the 1PPS timing outputs of 1E-11 on average. ___ 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] Terrestrial Tides and Land Movement
Hi Bob, Thanks for taking the time to explain the 4ns and 20ns wanders. I have just been calling them constellation errors without being able to explain it better than that. I've also wondered how much of the 20ns, if any, is attributable to the PRS-45A. I still don't have the antenna located in a position suitable for precision timing. The power of the HOA is not to be trifled with. That, and the sky is full of power lines and other junk around here. Bob From: Bob Camp kb...@n1k.org To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, May 25, 2015 6:01 PM Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Hi Let’s step back a bit: Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere. One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight path today. A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS and the like to improve things. A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to an LEA-8T (or similar). More sats is going to give you a better position solution. The bottom line is that an L1 GPSDO that wanders 10 to 20 ns per 24 hours compared to a Cesium or maser is doing pretty well. Taking that to 8 to 18 ns vs 12 to 22 is a worthy thing to do. *Proving* that a specific implementation better … maybe not so easy. I’ve seen a lot of plots of well respected eBay GPSDO’s that wander 30 ns or more (peak to peak) per day one day and 20 ns p-p the next…. Bob ___ 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] Terrestrial Tides and Land Movement
Hi Let’s step back a bit: Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere. One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight path today. A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS and the like to improve things. A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to an LEA-8T (or similar). More sats is going to give you a better position solution. The bottom line is that an L1 GPSDO that wanders 10 to 20 ns per 24 hours compared to a Cesium or maser is doing pretty well. Taking that to 8 to 18 ns vs 12 to 22 is a worthy thing to do. *Proving* that a specific implementation better … maybe not so easy. I’ve seen a lot of plots of well respected eBay GPSDO’s that wander 30 ns or more (peak to peak) per day one day and 20 ns p-p the next…. Bob On May 25, 2015, at 5:28 PM, Bob Stewart b...@evoria.net wrote: Hi Tom, I'm not sure what you mean by this 0D vs 3D. I'm using an LEA-6T. There are three time transfer modes 0=disabled, 1=survey-in, 2=fixed mode. Are you suggesting that I set it to disabled to run a test? I've never tried that. I know that if I monitor the output while doing a survey, the phase is all over the place. I'm in the middle of a therm correction test at the moment, but the plots at the link below are essentially where I am in development. The PRS-45A is driving the reference and start inputs of the 5370A. I'm using a somewhat modified PID system. http://evoria.net/AE6RV/Status/ Development is essentially over, at this point except for details, like adding code for the M12+ receiver. I can post a link to the schematic, if there's interest, but I've decided that the code will remain proprietary. This has turned into something a lot bigger than a $25 GPSDO engine. Bob From: Tom Van Baak t...@leapsecond.com To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com Sent: Monday, May 25, 2015 3:09 PM Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Hi Bob, You only need a survey if your timing receiver is running in zero-D mode. If you move the antenna more than some practical threshold you should adjust the fixed position or maybe just do another survey. If you plan to move a lot, or if your application is mobile, or are on a slippery slope, or you just don't want to bother with a time-consuming survey, then run the timing receiver in 3D mode. As I said it will perform almost as well. If you normally get, say 9 SV, I predict the timing accuracy difference is maybe only 10 or 20%. You're still building a homebrew GPSDO, right? Collect a day of performance data in 0-D and then a day in 3-D and see what difference there is in RMS timing residuals (or in ADEV). I wonder if your GPSDO can even measure the difference. /tvb - Original Message - From: Bob Stewart b...@evoria.net To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com Sent: Monday, May 25, 2015 11:09 AM Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Tom said: The nice thing about GPS, unlike other time transfer methods, is that can handle the case of a moving antenna. As the antenna moves so does the time. This is why GPS timing receivers work (almost as well) on top of your car as on top of your house. I don't get that. What's the purpose of doing a survey when you move your antenna if this the case? Bob ___ 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.
[time-nuts] pp2s? No, 1pps from a Nortel GPSTM!
As anyone with a Nortel GPSTM knows, it's a close cousin to the Thunderbolt but not exactly identical. Notably, coming from a CDMA environment, the unit has an even second output, aka PP2S, aka 0.5pps, aka 0.5Hz, etc. (Hoping to make this searchable...) There are software commands to configure this on the Thunderbolt too, but the GPSTM appears to have this function hard-coded into the PAL, and it can't be set back to PPS in software. However, there exists a PPS signal on the PCB, at TP13 between the Trimble chip and the PAL, discovered by some folks at the hackerspace here, during some noodling-around with an oscilloscope this afternoon. It's all documented here: https://www.i3detroit.org/wiki/Nortel_GPSTM This is for a NTBW50AA-11 module (single long board), other parts may have the signal in different places but I bet it's in there. Enjoy!-Nate B- ___ 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] pp2s? No, 1pps from a Nortel GPSTM!
Hi Nate, Nice page. Thanks for sharing your work. The Nortel units are a reasonable and slightly cheaper alternative to a TBolt, if you don't mind the much larger size, mass, and non-standard connector issues. The performance depends somewhat on which vendor's oscillator was used. I tested a bunch here: http://www.leapsecond.com/pages/nortel/ For NTP none of these plots matter (most GPSDO are a thousand to a million times more stable than NTP or a PC can handle). /tvb - Original Message - From: Nathaniel Bezanson mys...@telcodata.us To: time-nuts@febo.com Sent: Monday, May 25, 2015 7:08 PM Subject: [time-nuts] pp2s? No, 1pps from a Nortel GPSTM! As anyone with a Nortel GPSTM knows, it's a close cousin to the Thunderbolt but not exactly identical. Notably, coming from a CDMA environment, the unit has an even second output, aka PP2S, aka 0.5pps, aka 0.5Hz, etc. (Hoping to make this searchable...) There are software commands to configure this on the Thunderbolt too, but the GPSTM appears to have this function hard-coded into the PAL, and it can't be set back to PPS in software. However, there exists a PPS signal on the PCB, at TP13 between the Trimble chip and the PAL, discovered by some folks at the hackerspace here, during some noodling-around with an oscilloscope this afternoon. It's all documented here: https://www.i3detroit.org/wiki/Nortel_GPSTM This is for a NTBW50AA-11 module (single long board), other parts may have the signal in different places but I bet it's in there. Enjoy!-Nate B- ___ 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] 3048A software question
The easiest way of getting a new well supported version of DOS, is to download FreeDOS. Anything that worked on any version of MSDOS will run under FreeDOS... and so much more! -Chuck Harris davidh wrote: Folks, I'm also working on getting the MSDOS version running. What is the most recent version of DOS that people have found to work with the A 01.01 version. Also, can anyone advise where the command drivers for the 82335 can be found? Cheers, david ___ 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] 3048A software question
Folks, I'm also working on getting the MSDOS version running. What is the most recent version of DOS that people have found to work with the A 01.01 version. Also, can anyone advise where the command drivers for the 82335 can be found? Cheers, david Hi Adrian, Got the spec lines working now, thanks! Yes, the DOS version. I was hoping for an updated user manual for that version as the manual describes the other software version, and maybe a slightly later sw version. Oh well. Thanks for you help! Said On Feb 17, 2012, at 5:06, Adrian rfnuts-kvp5wt2u...@public.gmane.org wrote: Said, are you using the Opt. 311 (MS-DOS) software? I don't know of any more recent versions. To answer your initial question: You can not change anything on the diagram _after_ the measurement, not even the title. The spec lines will be visible only when you have defined them prior to starting the measurement. Regards, Adrian saidjack-ydxpq3io...@public.gmane.org schrieb: Hello team, I am trying to get an HP 3048A system up and running, and I am having problems with enabling spec limit lines on the graph. I can enter the spec line data under the manipulate results then spec lines menu, but the lines I entered are not visible. There are the standard spec lines visible when I do the internal noise floor test, so I know this should work. Does anyone know how to enable these properly? The user manual doesn't talk about this, and it is written for an older version of the software anyway's. Also, I have software version A 01.01 from 1994, does anyone have any more recent software version? Thanks in advance, Said ___ time-nuts mailing list -- time-nuts-jsktletq...@public.gmane.org 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-jsktletq...@public.gmane.org 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] LTC6957 internal architecture
With all this talk of the LT6957 I'm wondering if there's interest in a re-spin of my frequency divider with one of these at the front end instead. Regards, David Partridge -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 26 May 2015 00:40 To: time-nuts@febo.com Subject: [time-nuts] LTC6957 internal architecture The following patent hints that the LTC6957 front end probably consists of several cascaded long tailed pair differential amplifier stages each with a selectable bandwidth set by capacitors shunting the collector load resistors. : US8319551 The input limiter is in effect a Collins style limiter with selectable bandwidth for each stage to reduce the noise with respect to a comparator which typically has several high gain wide bandwidth cascaded differential amplifier stages. 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. ___ 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] FTS 8400
Ole - These became obsolete in 1999. Actually led to development of TAC-2 board (TAPR) in 1996. Tom Clark, K3IO could tell you about the FTS 8400 usage with the VLBI large dish array in 1980s and 1990s. Scroll down the TAC32Plus software notes for discussion on Trimble FTS 8400. https://www.cnssys.com/cnsclock/Tac32PlusSoftware.php Greg w9gb ___ 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] pp2s? No, 1pps from a Nortel GPSTM!
Moin Tom, On Tue, 26 May 2015 05:09:05 -0700 Tom Van Baak t...@leapsecond.com wrote: The performance depends somewhat on which vendor's oscillator was used. I tested a bunch here: http://www.leapsecond.com/pages/nortel/ The phase noise plots look a bit peculiar for unit 2 and 4. Do you have any guess where the humb at 4kHz comes from? Also the much higher amount of harmonics(?)/spikes of these two units raises some questions. Might it be that they use a different PLL structure as well? Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TymServe 2100 1995 Issue - A Kludgy Fix
descoubes kirjoitti: I am very pleased to inform you that the 1995 year bug on the TS2100 has been solved. You will have to replace the existing Trimble ACE III GPS receiver by our N024 with special firmware. Does this also correct the 1 sec offset caused by upcoming leap second? To remind, TS2100 GPS mode failed already in February, having 1 sec offset right after the information about upcoming leap second was added. How can we know that it doesn't fail again when actual GPS week rollover will happen? Now it seems to be week 1846 and 2047 will come less than four years. Did you test this with GPS simulator? Best regards, -- 73s! Esa OH4KJU ___ 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] Terrestrial Tides and Land Movement
Hi Bob S, An HOA can be a daunting problem, but not one that cannot be solved with a little guile. Every house I have ever seen that has modern plumbing has a few vent stacks on the roof. Would the HOA even notice if yours sprouted another one dark weekend evening? All the kit you need to add one to your roof is available at your local big box store. The usual bullet style antenna, sitting on top of a PVC vent pipe would be invisible on most houses, particularly if it were to be placed in the same vicinity as the rest. Also, GPS bullet antennas are pretty well sealed, save for the connector on the bottom. If you do a good job of sealing the connector (eg. lots of wraps of electrical tape, followed by a few of friction tape) there in no intrinsic reason you couldn't safely mount yours on top of the main plumbing vent stack. Drill a hole in the side at some convenient spot inside of the house, and snake the coax up through the vent stack, mount the antenna over the top, leaving adequate vent space. (OBTW, it isn't a vent stack until it is above the highest fixture in the house.) Although I don't have an HOA on my farm, I have my antenna mounted that way on my radon mitigation pipe. I bent up a couple of pieces of aluminum to make an open plug and put the antenna up without ever setting foot on my roof. I simply snaked the cable up and out the top of the radon pipe, and when I could reach it from a window, installed the GPS antenna, and aluminum plug, and then pulled the antenna cable back through the pipe, causing the plug and antenna to pop into the pipe mounting the antenna. -Chuck Harris Bob Stewart wrote: Hi Bob, Thanks for taking the time to explain the 4ns and 20ns wanders. I have just been calling them constellation errors without being able to explain it better than that. I've also wondered how much of the 20ns, if any, is attributable to the PRS-45A. I still don't have the antenna located in a position suitable for precision timing. The power of the HOA is not to be trifled with. That, and the sky is full of power lines and other junk around here. Bob ___ 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] Bls: time-nuts Digest, Vol 130, Issue 38
Dear All This is the first time I posted in this forum so please forgive me if its already discuss before I like to ask You who has more experience about my plan for USD75 GPSDO before I explain my plan let me tell You some real world limitation 1. The parts I choose must be available in local store (custom bussiness cost a lot of time) 2. I do not aim for something special a magnitude better than my MTI milliren OCXO is welcome. Now What in my mind I will use Ublox 7m GPS board that can program from 0,25Mhz to 10Mhz (https://sites.google.com/site/g4zfqradio/u-blox_neo-6-7) But the problem are I found someone (http://www.ra3apw.ru/proekty/ublox-neo-7m/) already do the spectrum analysis for this board and the result is like this : and the last picture is far better, correct ? so what I need to do I have 2 plan : 1. use the board 10Mhz output than use very narrow (100Hz bandwith) Crystal filter 2. Use the 4Mhz output than again filter it use Crystal filter to clean it than use it as reference for PLL for controling 10Mhz OCXO Which one you think a better way. last I also like to know because MTI only spec the OCXO model 240 harmonics to down to -30dB (http://www.mti-milliren.com/pdfs/240.pdf) is there any benefit to use a crystal filter in the output to clearer it more. any opinion is very welcome Thank You Anton Pada Selasa, 26 Mei 2015 23:00, time-nuts-requ...@febo.com time-nuts-requ...@febo.com menulis: Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Terrestrial Tides and Land Movement (Bob Camp) 2. Re: Terrestrial Tides and Land Movement (Bob Stewart) 3. pp2s? No, 1pps from a Nortel GPSTM! (Nathaniel Bezanson) 4. Re: FTS 8400 (Gregory Beat) 5. Re: 3048A software question (davidh) 6. Re: LTC6957 internal architecture (David C. Partridge) 7. Re: pp2s? No, 1pps from a Nortel GPSTM! (Tom Van Baak) 8. Re: 3048A software question (Chuck Harris) 9. Re: Terrestrial Tides and Land Movement (Chuck Harris) 10. Re: TymServe 2100 1995 Issue - A Kludgy Fix (Esa Heikkinen) -- Message: 1 Date: Mon, 25 May 2015 19:01:02 -0400 From: Bob Camp kb...@n1k.org To: Bob Stewart b...@evoria.net, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Terrestrial Tides and Land Movement Message-ID: c83d4da8-3e3d-462f-abff-3dae1f645...@n1k.org Content-Type: text/plain; charset=utf-8 Hi Let’s step back a bit: Your module is accurate to maybe 2 ns over a short period of time and something in the 10 to 20 ns range over 24 hours. The 2 ns comes from a variety of issues. The 20 ns comes mainly from the ionosphere. One example of a part of the 2 ns - the satellite positions in orbit are only known to some level of accuracy. The data your module gets is a broadcast data set that represents a “best guess” made yesterday to fit the fight path today. A GPS that does an on the fly position solution to 3M is not that exceptional these days. You certainly see claims of performance at the 1M or even 0.5M level. Yes people do fudge the numbers. Yes they do use WAAS and the like to improve things. A 3M error is at most a 10 ns timing error. It’s more likely to be a 3-4 ns timing error. That’s not all that big compared to the numbers above. Am I fudging the numbers a bit? Of course I am. There is an implicit assumption that the mobile platform has a good view of the sky. Dropping below 4 sats would not happen in this case. I’d also upgrade the LEA-6T to an LEA-8T (or similar). More sats is going to give you a better position solution. The bottom line is that an L1 GPSDO that wanders 10 to 20 ns per 24 hours compared to a Cesium or maser is doing pretty well. Taking that to 8 to 18 ns vs 12 to 22 is a worthy thing to do. *Proving* that a specific implementation better … maybe not so easy. I’ve seen a lot of plots of well respected eBay GPSDO’s that wander 30 ns or more (peak to peak) per day one day and 20 ns p-p the next…. Bob On May 25, 2015, at 5:28 PM, Bob Stewart b...@evoria.net wrote: Hi Tom, I'm not sure what you mean by this 0D vs 3D. I'm using an LEA-6T. There are three time transfer modes 0=disabled, 1=survey-in, 2=fixed mode. Are you suggesting that I set it to disabled to run a test? I've never tried that. I know that if I monitor the output while doing a survey, the phase is all over the place. I'm in the middle of a therm correction test at the moment, but the plots at the link
