Re: [time-nuts] hp10811-60111 on ebay
On 30 June 2010 02:46, Attila Kinali wrote: >> That would be the sort of gadget which would allow you to compare what >> ocxo devices you have. If you have a dedicated spectrum analyser that >> would allow you to look directly at phase-nose. There are a number of >> ways to determine such "quality" measurements and not all of them >> require a hefty outlay in test equipment. I wonder what you are trying >> to achieve with your search for a good ocxo as this may indicate what >> path is best for you. > > My goal is to build a GPSDO and to learn as much as possible > in the process. And while i'm at it, i'd like to get a > precission/accuracy that comes close to what can commercially > bought, if possible even better ;-) Are you planning on building one of the published designs or coming up with something of your own? If your really interested in this field you probably going to look at investing in at least a minimum of equipment that will produce accurate results. If you don't already have a good counter, I would suggest you start looking out for one in the usual places as if you search for a prolonged period you stand to pick up something at the "right" price for you. Get one that is as stable as you can afford and make sure it has some form of instrument buss. This would allow you to perform ADEV measurements either directly, if the counter is able to pre-trigger on a stop event, or you can perform a test using the picket fence method. Of course, you may be able to build up your own version of the TPLL setup using a phase detector and VtoF converter feeding into your sound card to count the number of cycles over a minimum tau period. Of course, this is a chicken and egg situation as you need a good reference oscillator to start with and if you have nothing so far then this will not work for you. There is the delay line method which only requires a single oscillator, the DUT, where you spit the oscillators output with a power divider or directional coupler and then pass one output through a delay line that is calculated to end up with the signal being 90 degrees out of phase with the undelayed version. Those two signals are then fed to a phase detector, through a low pass filter and to some method of measuring the residual components present. The product of the two out of phase signals to the phase detector will cancel out producing 0V when they are exactly 90 degrees apart but any other frequencies present will not be at 90 degrees so they will show up on the output. You could use this to simply compare sources without having absolute measurements, IE. simple test measurements, or obtain referenced measurements with appropriate equipment. > And as most of the parameters of the GPSDO are dictated by the > quality of the OCXO, i'd like to get some that are of good quality. > Or at least worth the money i pay for them. Without buying something off the shelf with a manufacturers test cert, you will have to start somewhere and choose an ocxo that should give you the best performance that your wallet can provide on the used market. The 10811 is a very well known and respected unit which comes in two basic variants, the single oven which has tuning screws and the double oven which does not. Obviously the double oven will perform better with a change in temperature but the jury is undecided on which is better wrt the ADEV performance. Buying a well used xtal should give you much better performance than a new one which has not been run-in. To start from scratch and produce a top quality performance GPSDO at the first try is quite a goal to reach but in performing the task you will learn a great deal about the subject and how you can improve things in the future. There is no reason why you cannot update the ocxo in your GPSDO later on when you find a better one as I think you will need to look at how your going to test these before you can achieve the best performance. Of course, you may be able to buy a used fully tested ocxo with tested ADEV if you can find someone who would sell that to you. Maybe someone on this list could help you out there. I have not expanded on the ideas above but if your interested I'm sure others or myself can come up with some useful links to assist you and help as well. Steve > > Attila Kinali > > -- > If you want to walk fast, walk alone. > If you want to walk far, walk together. > -- African proverb > > ___ > 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. > -- Steve Rooke - ZL3TUV & G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ 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] yet another GPSDO design, or so
Ah, now I get the basic idea. I'll need to think about it for a while. Many thanks for the links. Chris Stake -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 30 June 2010 09:08 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] yet another GPSDO design, or so Here's a link to a pdf version of the synchronously filtered low ripple pwm dac: http://www.edn.com/contents/images/6553625.pdf Bruce Bruce Griffiths wrote: > Chris > > All the details are in the article: > http://www.edn.com/contents/images/6607197.pdf > > However it would be best to read the article posted by Bob Camp first: > > > Bruce > > Chris Stake wrote: >> Hi Bruce, >> This sounds like a promising idea, please could you expand on the >> synchronous filter technique? I have seen some articles about how such >> filters can be used to "clean up" the data from rotating machinery for >> vibration analysis etc. but I don't follow how they can be used in a PWM >> application. >> Regards >> Chris Stake >> >> >> >> Its possible to build a 24 bit resolution D/A using a synchronously >> filtered PWM circuit. >> A pair of PWM outputs and a few relatively low precision resistors and >> capacitors together with a low noise low drift reference are required. >> The technique takes advantage of the fact that the required EFC voltage >> changes slowly and isnt updated at a highg rate. >> The synchronous filter technique eliminates the very long time constant >> RC filters required with an asynchronously filtered PWM waveform. >> >> 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. >> > > > > ___ > 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] Scientists measure shortest ever time interval
On 06/30/2010 10:03 AM, Raj wrote: Thanks Mike. I was wondering myself Doc as how they did it. I was skeptical when a friend mentioned it. The quick check of their article didn't give me much info... but I was tired and somewhat drunk, so it may have played into it. It you have a repetitive pattern, you can look at the energy spurs and deduct the pulse width that way. Monitoring the intensity of a nummber of side-band frequencies should not be impossible. But that is just a wild guess... 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] yet another GPSDO design, or so
Here's a link to a pdf version of the synchronously filtered low ripple pwm dac: http://www.edn.com/contents/images/6553625.pdf Bruce Bruce Griffiths wrote: Chris All the details are in the article: http://www.edn.com/contents/images/6607197.pdf However it would be best to read the article posted by Bob Camp first: Bruce Chris Stake wrote: Hi Bruce, This sounds like a promising idea, please could you expand on the synchronous filter technique? I have seen some articles about how such filters can be used to "clean up" the data from rotating machinery for vibration analysis etc. but I don't follow how they can be used in a PWM application. Regards Chris Stake Its possible to build a 24 bit resolution D/A using a synchronously filtered PWM circuit. A pair of PWM outputs and a few relatively low precision resistors and capacitors together with a low noise low drift reference are required. The technique takes advantage of the fact that the required EFC voltage changes slowly and isnt updated at a highg rate. The synchronous filter technique eliminates the very long time constant RC filters required with an asynchronously filtered PWM waveform. 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. ___ 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] yet another GPSDO design, or so
Chris All the details are in the article: http://www.edn.com/contents/images/6607197.pdf However it would be best to read the article posted by Bob Camp first: Bruce Chris Stake wrote: Hi Bruce, This sounds like a promising idea, please could you expand on the synchronous filter technique? I have seen some articles about how such filters can be used to "clean up" the data from rotating machinery for vibration analysis etc. but I don't follow how they can be used in a PWM application. Regards Chris Stake Its possible to build a 24 bit resolution D/A using a synchronously filtered PWM circuit. A pair of PWM outputs and a few relatively low precision resistors and capacitors together with a low noise low drift reference are required. The technique takes advantage of the fact that the required EFC voltage changes slowly and isnt updated at a highg rate. The synchronous filter technique eliminates the very long time constant RC filters required with an asynchronously filtered PWM waveform. 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. ___ 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] Scientists measure shortest ever time interval
Thanks Mike. I was wondering myself Doc as how they did it. I was skeptical when a friend mentioned it. Raj At 30-06-10, you wrote: >details at > >http://www.attoworld.de/ > >On Tue, Jun 29, 2010 at 12:14 PM, NE8S wrote: > >> Greetings, Raj, >> >> Many thanks for the reference that you provided. >> >> I wonder on what method was utilized in them achieving this 20 attosecond >> measurement? Nothing was mentioned as to the instrumentation utilized in >> this time metrology. >> >> Doc >> NE8S >> >> - Original Message - From: "Raj" >> To: "Time Nuts" >> Sent: Tuesday, June 29, 2010 10:19 AM >> Subject: [time-nuts] Scientists measure shortest ever time interval >> >> >> >> From one of our papers >>> >>> http://timesofindia.indiatimes.com/articleshow/6090902.cms >>> >>> Cheers >>> >>> -- >>> Raj, VU2ZAP >>> Bangalore, India. >>> >>> ___ 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] Motion effects on accuracy of GPS pps
Thanks Didier, There's also some useful information on the subject here: http://www.greenrayindustries.com/accsens_tb3.html Regards, Dan Didier Juges wrote: From memory, I believe tvb did some experiments with an OCXO or Rb measuring AVAR while flipping the oscillator upside down (+/- 1g). You may find links on tvb's web site www.leapsecond.com At the moment, I cannot find the link... Didier PS: Note to tvb: Tom, when you have time, a search or indexing feature on your web site would be very useful. Apparently, Google is not able to find much of the excellent resources and data you have, maybe because many pages are not linked through the main page? Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Daniel Davson Sender: time-nuts-boun...@febo.com Date: Tue, 29 Jun 2010 15:11:19 To: Discussion of precise time and frequency measurement Reply-To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Motion effects on accuracy of GPS pps Thanks for the response Björn. Also thanks to Didier Juges for pointing out that this has been covered on a previous thread. I'll go and find it in the history. Unfortunately the device will be used in urban areas so some multipath & obstruction of skyview is expected. I've just done some testing on my OCXO and it has a maximum sensitivity of about 5 ppb / *g*, which is notable, but shouldn't present a problem. I've yet to explore the vibration effects - thanks for pointing my attention to the motion effects on the OCXO itself, its an aspect I'd otherwise have overlooked. Daniel b...@lysator.liu.se wrote: > Hi Daniel, > > >> Hi, >> >> I've recently completed a GPSDO using the pps output of a uBlox Antaris >> TIM4 GPS module to discipline a 10MHz OCXO. I'm now investigating the >> motion effects (acceleration/uniform velocity) on the accuracy of the >> time-pulse and hence on my frequency output. >> > > Are you moving around in areas with little obstruction for the GPS antenna > towards the sky? Then I would first look at the dynamics inpact on your > OCXO. > > >> I've been unable to find any detailed information on the relationship >> between the accuracy of the pps output and the effects of having the >> receiver in motion (i.e. in a car/boat, at velocities far below the >> modules operating limit of 515m/s) - I'd appreciate some input on this >> matter. Does motion cause increased jitter? >> > > Tilting/accelerating your GPS oscillator might possibly yield an effect. > Other than that there is no theoretical advantage keeping your receiver > stationary. All its measurements are done against satellites moving at ca > 4km/s. > > -- Daniel Davson HW Design Engineer Peralex Electronics (pty) ltd. Peralex House, 5 Dreyersdal Rd, Bergvliet 7945, South Africa Tel: +27 21 710 7446 Disclaimer: http://www.peralex.com/disclaimer.html ___ 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.
