Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

Yo MLewis! On Thu, 2 Nov 2017 21:54:57 -0400 MLewis wrote: > I have no idea what the temperature is inside the chamber. I use the 'temper' to know what temp is in my GPS chamber: https://www.amazon.com/TEMPer-USB-Thermometer-w-Alerts/dp/B002VA813U I use that, and an

Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

Earlier this week, I put the breakout board with my NEO-M8T into an aluminum can. The can is split into a lower half and an upper half. The lower half was insulated on its sides internally, but open to the upper half, which wasn't insulated. The lower area contains the NEO-M8T on its breakout

Re: [time-nuts] time-c-b.nist.gov replaces time-c.timefreq.bldrdoc.gov on Oct. 5th

Judging by http://tf.nist.gov/tf-cgi/servers.cgi, the current round of NIST server changes is complete. All of the new servers now respond to requests from my NTP client. A number of NIST and USNO ( http://tycho.usno.navy.mil/NTP/ ) sites are no longer supported. On Tue, Oct 3, 2017 at 1:10

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi I believe you indeed have tied this back to a number of papers …. Bob > On Nov 2, 2017, at 5:45 PM, Leo Bodnar wrote: > > This is, essentially, how modern delta-sigma DACs work while achieving 24-bit > and higher precision using only a single bit converter internally

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

This is, essentially, how modern delta-sigma DACs work while achieving 24-bit and higher precision using only a single bit converter internally and a lot of clever digital filtering. Multiple loops are what would be called "higher order" in delta-sigma parlance. Delta-sigma tech is not poor

Re: [time-nuts] HP 5335A Question

> The designers very well designed two near inifinite counter chains inside the > 5335A.. > I got my wisdom from the hp journal 9-1980. http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1980-09.pdf > They used a digital ASIC, called the MRC, multi-register counter, and it > allows counting > of

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

Hi There’s no particular reason to stop at the 100:1 point. You can run multiple loops at the same time and get out to essentially any level of precision. The only question is over what averaging interval the precision applies. In some cases this elastic definition does just fine. Bob > On

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

>> The DS3231 has an 8 bit register that will change its frequency in >> increments of about 0.1ppm. Thus you could discipline it to get its pps >> aligned with your reference. > > That sounds like you just designed the worst GPSDO ever. You could argue that the worst GPSDO ever is an operating

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Thu, Nov 2, 2017 at 9:04 AM, Chris Caudle wrote: > > > That sounds like you just designed the worst GPSDO ever. > > -- > Chris Caudle > > Yes but the price and power consumption are right. I guess it all depends on your application... -- --Jim Harman

Re: [time-nuts] HP 5335A Question

Hi They may have intended to have infinite resolution. The net result in the real counter is that you get MSB rollover. The LSB’s are correct pretty much forever and ever. The same math tricks mentioned before can be used to get high resolution on the display once you get the gate running.

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Wed, November 1, 2017 7:16 pm, Jim Harman wrote: > The DS3231 has an 8 bit register that will change its frequency in > increments of about 0.1ppm. Thus you could discipline it to get its pps > aligned with your reference. That sounds like you just designed the worst GPSDO ever. -- Chris

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

On Thu, November 2, 2017 5:19 am, Hal Murray wrote: > I'd let the RTC free run, feed its PPS to a "clock" program, and then feed > the offset to ntpd via SHM. I would just get a GPS that doesn't shut off the PPS when it loses lock and that has a decent TCXO for the clock. Or just use a rubidium

[time-nuts] HP 5335A Question

  >The gate time on a 5335 can be set via GPIB. It can be set to some *very* long gates (well past 100 seconds). >When you do this, the data reported on GPIB does “stretch” to cover the added >digits. The problem is that there >are internal register overflows. The designers did not

Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

mlewis...@rogers.com said: > - GPS module's secondary PPS disciplining the RTC-counter-divider PPS by > resetting the RTC's counter/divider (I'm assuming there's one that will > rest fast enough to sync; I've never looked into these...) How many RTCs accept an external PPS? Your plan sounds