Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On 29 Feb 2016, at 10:46 am, Hal Murray wrote: > What distro are you starting with? > > I'm using Debian. Their kernel includes PPS support, both Wheezy and Jessie. I’m using Raspbian Jessie. PPS over GPIO is now recognised in the stock kernel but kernel PPS isn’t. I

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

nc...@hotmail.co.uk said: > and building a custom kernel for the Raspberry Pi to include KPPS What distro are you starting with? I'm using Debian. Their kernel includes PPS support, both Wheezy and Jessie. > I had a DS3231 lying around so, ... Are you setup to make long term measurements?

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On 25 Feb 2016, at 9:07 pm, Jim Harman wrote: > On Thu, Feb 25, 2016 at 1:08 PM, Neil Green wrote: > >> I’ve decided to build this: >> >> http://www.hackersbench.com/Projects/1Hz/ > > Good start! > > Once you have built it and observed how sensitive

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On Thu, Feb 25, 2016 at 1:08 PM, Neil Green wrote: > I’ve decided to build this: > > http://www.hackersbench.com/Projects/1Hz/ > > which has an easy to follow diagram. Parts have cost less than £5. I’m not > expecting great things from it by any means, but it’s something I

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On 24 Feb 2016, at 6:50 pm, Hal Murray wrote: > How good is your antenna? How often does your current GPS setup run out of > satellites? It’s a puck antenna placed in a window. I rent, so having an external antenna installed unfortunately isn’t an option. I’ve never

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On 24 Feb 2016, at 4:30 pm, Chris Albertson wrote: > A simple GPSDO is, well, simple. All you do is compare the phase of > the PPS to the phase of the 10MHz crystal and then adjust the > frequency of the crystal to keep the phase difference constant. Can > be done

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On 24 Feb 2016, at 3:08 pm, David J Taylor wrote: > A BeagleBone Black might give half the jitter compared to the RPi, but not > the order of magnitude you may be seeking. > > http://www.satsignal.eu/ntp/BBB-vs-RPi.html > > Perhaps purely for serving the pool,

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

My DAC is the ones built into the processor chip. They are only 8-bits wide but you can combine two of them by adding First reducing one of them by a factor of 256 then adding them. There is a small discontinuity but software addresses that Si I get a decent 15-bit DAC for free As for the

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

Pete Stephenson wrote: > On Wed, Feb 24, 2016 at 3:22 PM, Neil Green wrote: >> I currently operate a stratum 1 NTP server in the NTP pool using a U-Blox >> Max-7Q GPS module with PPS attached to, variously, a Raspberry Pi via GPIO >> or a Celeron mini PC via serial DB-9.

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On Wed, Feb 24, 2016 at 2:53 PM, Nick Sayer via time-nuts < time-nuts@febo.com> wrote: > I can measure 1 ppb, but it takes 1000 seconds to do it ... My > understanding is that better GPSDOs are able to provide for more granular > phase detection. It doesn't take a lot of hardware to get about

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

Hi WWVB DSO’s were a pretty common thing back in the 70’s and 80’s. You could hold fractions of a ppm with them. With manual intervention / scheduling you could get into the “couple ppb” range on a good week. Comparative numbers would be 1x10^-11 on a GPSDO. All the same qualifiers about

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

Hi The tick is a burst of audio at a fairly low frequency. You are going to need pretty good conditions to get 0.1 ms. The fade process over much of the day will spread that out a *lot*. Bob > On Feb 24, 2016, at 5:11 PM, Tim Shoppa wrote: > > Hal - > In my experience

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

Hi If you are looking at pool service, the first question would be how you connect to the backbone. If you are running something asymmetric (DSL / cable modem) you already have enough of an offset that it alone it far bigger than any other error in your system. Even with fancier

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

Hal - In my experience over more than a decade, the ntpd WWV audio refclock has jitter circa 0.1ms. This is not nanosecond-time-nut PPS territory. But it is more than good enough for WAN ntpd. I use a Ten-Tec RX-320 as a cheap frequency-agile receiver for WWV. In between 5MHz/10MHz/15MHz

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

> From what others on the list have said before, WWVB offers performance > that's at least a couple orders of magnitude worse than GPS, even if you > correct for all of the expected diurnal variations in LF propagation. Given > that a fairly pedestrian GPS module offers a nominal PPS accuracy of

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

> On Feb 24, 2016, at 8:30 AM, Chris Albertson > wrote: > > On Wed, Feb 24, 2016 at 6:22 AM, Neil Green wrote: > >> >> What would be my next step up be, hardware-wise, in terms of improving >> precision, stability, etc? A GPSDO? Budget is

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

What would be my next step up be, hardware-wise, in terms of improving precision, stability, etc? A GPSDO? Budget is limited as far as these things go - about £150 UK/$210 US. I have Symmetricom TS2100 with OCXO and GPS upgrades as primary server, accessible only at local network. It has

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

tsho...@gmail.com said: > My opinion if you want to serve reliable time through a longer GPS outage: > add a WWV or WWVB based radio clock. e.g. a shortwave radio and https:// > www.eecis.udel.edu/~mills/ntp/html/drivers/driver36.html Do you have any graphs comparing WWV or WWVB to GPS when

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

nc...@hotmail.co.uk said: > What would be my next step up be, hardware-wise, in terms of improving > precision, stability, etc? A GPSDO? Budget is limited as far as these things > go - about £150 UK/$210 US. How good is your antenna? How often does your current GPS setup run out of

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On Wed, Feb 24, 2016 at 6:22 AM, Neil Green wrote: > > What would be my next step up be, hardware-wise, in terms of improving > precision, stability, etc? A GPSDO? Budget is limited as far as these things > go - about £150 UK/$210 US. Given that you already have the GPS

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

GPSDO's are very nice if you want a bench source for calibration purposes. On the subject of NTP servers... GPSDO's would be relevant when doing holdover through a GPS outage measured in days. My opinion if you want to serve reliable time through a longer GPS outage: add a WWV or WWVB based

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

On Wed, Feb 24, 2016 at 3:22 PM, Neil Green wrote: > I currently operate a stratum 1 NTP server in the NTP pool using a U-Blox > Max-7Q GPS module with PPS attached to, variously, a Raspberry Pi via GPIO or > a Celeron mini PC via serial DB-9. The machine does nothing but

Re: [time-nuts] Next step up from basic GPS/PPS timekeeping

I currently operate a stratum 1 NTP server in the NTP pool using a U-Blox Max-7Q GPS module with PPS attached to, variously, a Raspberry Pi via GPIO or a Celeron mini PC via serial DB-9. The machine does nothing but serve time to the pool. Operating systems of choice are Debian or FreeBSD.

[time-nuts] Next step up from basic GPS/PPS timekeeping

I currently operate a stratum 1 NTP server in the NTP pool using a U-Blox Max-7Q GPS module with PPS attached to, variously, a Raspberry Pi via GPIO or a Celeron mini PC via serial DB-9. The machine does nothing but serve time to the pool. Operating systems of choice are Debian or FreeBSD.