Re: [time-nuts] Looking for GPSDO for home use
From: Chris Albertson If you are going to buy and set up a GPS receiver. The hardest part is the antenna. It is best if it can see the entire sky, horizon to horizon and if it is not near any reflecting surfaces. It is best if the antenna is mounted on a mast on the tallest building but a modern GPS will work if the antenna is playing on the desk near a window. You can connect a computer and get software to plot data from inside the GPS but really all you need to go is apply power and get the PPS. The old Motorola Oncore series of GPS is reliable and low cost. The UT has a PPS one sigma error of about 50 nanoseconds which is good enough they sell for under $20. The current new state of the art version is about $60 or $35 used. Here is an example Motorola-UT-Plus-Oncore-Timing-GPS-Modulehttp://www.ebay.com/itm/ONLY-1PSC-Motorola-UT-Plus-Oncore-Timing-GPS-Module-1pps-NTP-/301132856857?pt=US_Ham_Radio_Transmittershash=item461ceabe19 Be SURE to buy the timing version. There are non-timing or navigation versions. Make sure it says timing in the description. GPS receivers spew out tons of data but you can ignore it all. All you need is the PPS signal. Chris Albertson === Chris, Thanks for your comments and advice - I agree based on my years of experience with using GPS modules for NTP! The comments on antennas is particularly relevant as I have just placed an antenna outdoors for use with my Rapco GPSDO, and it has made a stunning difference to this unit from the last century. All the units purchased this century (except the GPS 18 LVC, not the 18x) are much more sensitive and work well enough indoors - at least at this location on the second floor of a two-storey building. The Arduino version piqued my interest, so the information on that is appreciated as well. 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] Looking for GPSDO for home use
Having done extensive testing on the ublox 6M that you can buy with antenna for less than $ 23 new from DX.com I can say with certainty that the 1 Hz pulse is better than 1 E-9 accurate, closer to E-10. Depending on the counter it could be used to adjust a frequency counter to that accuracy. I am not talking time, it does have a saw tooth element but the period is constant. Before some one says for an extra $ 20 you can get the T version I have one with M12 imulator and M12+'s, but the challenge is in making low cost do great things. We do not have the time but some one may want to explore using a PlL with a VCXO using the ! KHz that the 6M can be programmed to. Depending how the 1 KHz is generated and the proper filter 1 E-10 may be a possibility. Bert Kehren In a message dated 4/16/2014 11:07:21 A.M. Eastern Daylight Time, albertson.ch...@gmail.com writes: On Tue, Apr 15, 2014 at 10:09 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: [] Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Any GPS receiver with 1PPS is OK.All PPS signals are interchangeable. It is just a 5 volt 1Hz square wave. The raising edge of the wave is right at the tick of a new second. The GPSDO is simple too. It counts the cycles of the 10MHz oscillator from one PPS raising edge to the next and it should get exactly 10,000,000 cycles. If more or less are counted the software moves the voltage on OXCO's control pin up or down. Controllers can be more complex, but this much will get you started. The simplest next step is to count for 10 seconds and get to 0.1 Hz then add an interpolator and get to milli Hz If you are going to buy and set up a GPS receiver. The hardest part is the antenna. It is best if it can see the entire sky, horizon to horizon and if it is not near any reflecting surfaces. It is best if the antenna is mounted on a mast on the tallest building but a modern GPS will work if the antenna is playing on the desk near a window. You can connect a computer and get software to plot data from inside the GPS but really all you need to go is apply power and get the PPS. The old Motorola Oncore series of GPS is reliable and low cost. The UT has a PPS one sigma error of about 50 nanoseconds which is good enough they sell for under $20. The current new state of the art version is about $60 or $35 used. Here is an example Motorola-UT-Plus-Oncore-Timing-GPS-Modulehttp://www.ebay.com/itm/ONLY-1PSC- Motorola-UT-Plus-Oncore-Timing-GPS-Module-1pps-NTP-/301132856857?pt=US_Ham_R adio_Transmittershash=item461ceabe19 Be SURE to buy the timing version. There are non-timing or navigation versions. Make sure it says timing in the description. GPS receivers spew out tons of data but you can ignore it all. All you need is the PPS signal. -- 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] Looking for GPSDO for home use
Having done extensive testing on the ublox 6M that you can buy with antenna for less than $ 23 new from DX.com I can say with certainty that the 1 Hz pulse is better than 1 E-9 accurate, closer to E-10. Depending on the Hi Bert, There are lots of cheap GPS/1PPS receivers out there these days. Having tested many GPS receivers myself, let me help you out. I understand the number $23. But the number 1 E-9 by itself means nothing. Like, are you talking time or frequency? There's a big difference. Tell us if your number is timing accuracy or units of frequency accuracy or stability. Also either way, the measurement interval (or tau) is critical: a) If it's timing, then the units are usually seconds; e.g., 1 ns, peak-to-peak, or rms or even something like TDEV(tau) -- and tau is important. b) If it's frequency, then the units of absolute frequency accuracy or relative frequency stability; e.g., 0.01 Hz out of 10 MHz over some tau, or MDEV/ADEV(tau) -- and tau is critical. I say this because: a) If the 1e-9 or 1e-10 number you quote is rms time accuracy, then you have a GPS receiver better than what NIST or USNO has! b) If the 1e-9 or 1e-10 number you quote is frequency stability over a day, then you have the worst GPS receiver we've ever seen! So please clarify your units, or share raw data, or plots, or something. It's rather important. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for GPSDO for home use
If you are looking to build your first GPSDO. I'd go with the simplest one first. I had a goal to build and document one that did not require a custom PCB or programmed chip or any special test equipment other then a DMM and a scope with price well under $50. I've beat the price by a lot but not documentation yet. [] = Looking forward to seeing the circuit diagram and downloading the code, Chris! From previous experience there will be folk wanting a no soldering option, so if you can persuade someone to provide a ready-made board, so much the better 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] Looking for GPSDO for home use
On Tue, Apr 15, 2014 at 10:09 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: [] Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Any GPS receiver with 1PPS is OK.All PPS signals are interchangeable. It is just a 5 volt 1Hz square wave. The raising edge of the wave is right at the tick of a new second. The GPSDO is simple too. It counts the cycles of the 10MHz oscillator from one PPS raising edge to the next and it should get exactly 10,000,000 cycles. If more or less are counted the software moves the voltage on OXCO's control pin up or down. Controllers can be more complex, but this much will get you started. The simplest next step is to count for 10 seconds and get to 0.1 Hz then add an interpolator and get to milli Hz If you are going to buy and set up a GPS receiver. The hardest part is the antenna. It is best if it can see the entire sky, horizon to horizon and if it is not near any reflecting surfaces. It is best if the antenna is mounted on a mast on the tallest building but a modern GPS will work if the antenna is playing on the desk near a window. You can connect a computer and get software to plot data from inside the GPS but really all you need to go is apply power and get the PPS. The old Motorola Oncore series of GPS is reliable and low cost. The UT has a PPS one sigma error of about 50 nanoseconds which is good enough they sell for under $20. The current new state of the art version is about $60 or $35 used. Here is an example Motorola-UT-Plus-Oncore-Timing-GPS-Modulehttp://www.ebay.com/itm/ONLY-1PSC-Motorola-UT-Plus-Oncore-Timing-GPS-Module-1pps-NTP-/301132856857?pt=US_Ham_Radio_Transmittershash=item461ceabe19 Be SURE to buy the timing version. There are non-timing or navigation versions. Make sure it says timing in the description. GPS receivers spew out tons of data but you can ignore it all. All you need is the PPS signal. -- 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] Looking for GPSDO for home use
From: Chris Albertson I'm using (most of) the circuit posted a few weeks ago to this list by Lars Walenius. I posted the code here a week or so ago. I was impressed by how simple his GPSDO was and have sense simplified his design even more. The goal was not state of the art performance but an ultra simple design and low cost. Cost is about $8 another is about two dozen lines of code. [] Ah, Thanks, Chris. I haven't been following too closely, so I thought the whole things was $8, with just the Arduino alone. Perhaps if you do put in all on a Web page quite a few would be interested. If no-one else can, I could host the Web page. Thanks, 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] Looking for GPSDO for home use
Tom: I saw you post to David on the Time Nuts list offering availability of a Thunderbolt. If you have additional units available I would be interested in one as well. Let me know if you have any available and the cost. Thanks, Mike George N3MUY On 4/15/2014 14:03, Tom Van Baak wrote: Dave, If you're just calibrating a frequency counter you may not need a GPSDO. A simple GPS 1PPS is all you need; just measure the time from the 1PPS to the 10 MHz, wait a minute or an hour or a day and do it again. This will show you the time drift, from which you can calculate the frequency error. Still, having a 10 MHz GPSDO available is usually more convenient, so I would not talk you out of it. If you don't want to spend time to design your own GPSDO, or to build one of the dozen homebrew projects on the web, I would recommend you get a Trimble Thunderbolt. They are as turn-key as you can get, but also allow great hacking if you so choose. I have some left over from the group buy. If you're interested contact me off-list. Thanks, /tvb - Original Message - From: David Feldman wb0...@yahoo.com To: time-nuts@febo.com Sent: Tuesday, April 15, 2014 8:27 AM Subject: [time-nuts] Looking for GPSDO for home use I found this reflector after searching for GPSDO that would be suitable for individual purchase/use. Each time I found an article about GPSDO projects, that lead me to a surplus GPS module that is either no longer available, not current production, undocumented, or otherwise difficult to source. I don't mind doing my own building/integration, and am not adverse to starting with a used or suplus component, I'm not sure where to start in terms of sourcing the GPS module/antenna/etc. My main need is for something to serve as a primary frequency standard (i.e., 10 MHz output) I can use to set a voltage controlled OCXO I just installed in my (otherwise cheap chinese) frequency counter. It seems there are some modules that have/had 10 kHz output; that would work too. Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Thanks! Dave wb0...@yahoo.com ___ 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] Looking for GPSDO for home use
I found this reflector after searching for GPSDO that would be suitable for individual purchase/use. Each time I found an article about GPSDO projects, that lead me to a surplus GPS module that is either no longer available, not current production, undocumented, or otherwise difficult to source. I don't mind doing my own building/integration, and am not adverse to starting with a used or suplus component, I'm not sure where to start in terms of sourcing the GPS module/antenna/etc. My main need is for something to serve as a primary frequency standard (i.e., 10 MHz output) I can use to set a voltage controlled OCXO I just installed in my (otherwise cheap chinese) frequency counter. It seems there are some modules that have/had 10 kHz output; that would work too. Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Thanks! Dave wb0...@yahoo.com ___ 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] Looking for GPSDO for home use
Dave, If you're just calibrating a frequency counter you may not need a GPSDO. A simple GPS 1PPS is all you need; just measure the time from the 1PPS to the 10 MHz, wait a minute or an hour or a day and do it again. This will show you the time drift, from which you can calculate the frequency error. Still, having a 10 MHz GPSDO available is usually more convenient, so I would not talk you out of it. If you don't want to spend time to design your own GPSDO, or to build one of the dozen homebrew projects on the web, I would recommend you get a Trimble Thunderbolt. They are as turn-key as you can get, but also allow great hacking if you so choose. I have some left over from the group buy. If you're interested contact me off-list. Thanks, /tvb - Original Message - From: David Feldman wb0...@yahoo.com To: time-nuts@febo.com Sent: Tuesday, April 15, 2014 8:27 AM Subject: [time-nuts] Looking for GPSDO for home use I found this reflector after searching for GPSDO that would be suitable for individual purchase/use. Each time I found an article about GPSDO projects, that lead me to a surplus GPS module that is either no longer available, not current production, undocumented, or otherwise difficult to source. I don't mind doing my own building/integration, and am not adverse to starting with a used or suplus component, I'm not sure where to start in terms of sourcing the GPS module/antenna/etc. My main need is for something to serve as a primary frequency standard (i.e., 10 MHz output) I can use to set a voltage controlled OCXO I just installed in my (otherwise cheap chinese) frequency counter. It seems there are some modules that have/had 10 kHz output; that would work too. Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Thanks! Dave wb0...@yahoo.com ___ 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] Looking for GPSDO for home use
If you are looking to build your first GPSDO. I'd go with the simplest one first. I had a goal to build and document one that did not require a custom PCB or programmed chip or any special test equipment other then a DMM and a scope with price well under $50. I've beat the price by a lot but not documentation yet. My Arduino based GPSDO is back in operation. It is literally the simplest one that can still work.It's about $8 in parts but I've disconnected one of the external chips and will try removing the remaining one. The total BOM then will be just a bare Arudion Pro Mini, three resisters and two capacitors for about $4. It is back up and running now for about 12 hours. I have the output of the simple GPSDO and the 10MHz signal from a Trimble Thunderbolt both up on my dual trace scope. The two 10MHz signals do move slowly relative tone another. It will move to the right for 20 or 30 minutes then moves back left. But it is already better than you'd need to calibrate a frequency counter. The little AVR chip inside the Adruino has all the hardware you need, a fast counter that can be captured with a raising edge of a pulse and several DACs and ADCs. That is all I'm using right now. In the past people used to have to build this using small scale ICs. (maybe 74xxx type) There are at least a half dozen ways to make this better. The goal of this project is to see which makes the most difference and order them by bang per buck On Tue, Apr 15, 2014 at 11:03 AM, Tom Van Baak t...@leapsecond.com wrote: Dave, If you're just calibrating a frequency counter you may not need a GPSDO. A simple GPS 1PPS is all you need; just measure the time from the 1PPS to the 10 MHz, wait a minute or an hour or a day and do it again. This will show you the time drift, from which you can calculate the frequency error. Still, having a 10 MHz GPSDO available is usually more convenient, so I would not talk you out of it. If you don't want to spend time to design your own GPSDO, or to build one of the dozen homebrew projects on the web, I would recommend you get a Trimble Thunderbolt. They are as turn-key as you can get, but also allow great hacking if you so choose. I have some left over from the group buy. If you're interested contact me off-list. Thanks, /tvb - Original Message - From: David Feldman wb0...@yahoo.com To: time-nuts@febo.com Sent: Tuesday, April 15, 2014 8:27 AM Subject: [time-nuts] Looking for GPSDO for home use I found this reflector after searching for GPSDO that would be suitable for individual purchase/use. Each time I found an article about GPSDO projects, that lead me to a surplus GPS module that is either no longer available, not current production, undocumented, or otherwise difficult to source. I don't mind doing my own building/integration, and am not adverse to starting with a used or suplus component, I'm not sure where to start in terms of sourcing the GPS module/antenna/etc. My main need is for something to serve as a primary frequency standard (i.e., 10 MHz output) I can use to set a voltage controlled OCXO I just installed in my (otherwise cheap chinese) frequency counter. It seems there are some modules that have/had 10 kHz output; that would work too. Even 1 PPS output seems like a workable starting point, but at the expense of a different and/or more difficult path to get to a 10 MHz reference signal I seek. Any advance or pointer to source (reasonable cost, whatever that means!) would be appreciated. Thanks! Dave wb0...@yahoo.com ___ 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. -- 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.
