Re: [time-nuts] Best Chance GPS module

Ok. It wasn’t totally clear from your earlier message what you were looking at, but just be aware that the LED pin is just a “blinkenlichten” pin that means almost nothing. You have to actually separately look at the PPS pin to see what it’s doing. There’s (almost) no connection between the

Re: [time-nuts] Best Chance GPS module

On Dec 1, 2016, at 7:44 AM, David J Taylor wrote: Venus838LPX-T. Seems to go into a non-locked state for a proportion of the time but still emits a PPS signal, which increasingly deviates from true UTC. That's using a 25 mm square 28 dB active patch

Re: [time-nuts] Best Chance GPS module

Was the LED on the PPS pin or on the FIX pin? The FIX pin is nothing like the PPS output. Frankly, I’m not 100% sure what the rules are for it. When things are working properly, it blinks at 0.5 Hz, but the leading and trailing edges are something like 120-150 msec after the second. It’s very,

Re: [time-nuts] Best Chance GPS module

Hi If you watch the “jump” process. The thing that inevitably is being added or subtracted is a long path sat. For timing those are the worst of the bunch. Unless you have a way to fully correct the ionosphere (really good data or a multi band receiver) they will always be contributing an

Re: [time-nuts] Best Chance GPS module

Hi A 12 hour survey done with WAAS turned on is likely to be better than one with WAAS turned off. How good a 96 hour survey with WAAS on and off is something of a toss up. Bob > On Dec 4, 2016, at 1:35 PM, Chris Albertson wrote: > > On Sun, Dec 4, 2016 at 9:16

Re: [time-nuts] Best Chance GPS module

On Sun, Dec 4, 2016 at 9:16 AM, Mark Sims wrote: > For some unmentioned reason Ublox recommends disabling WAAS for precision > time applications. Doesn't make much sense to me > > It turns out that your self-survey position is much better then a WAAS correct position.

[time-nuts] Best Chance GPS module

The Trimble timing receivers have a "single satellite" operating mode that says to only use the highest elevation satellite that it sees (or you can set a specific single satellite to track). It would be interesting to see how the performance compares to its standard "overdetermined clock"

Re: [time-nuts] Best Chance GPS module

Hi That is the standard recommendation from all of the module manufacturers when running in timing (as opposed to survey) mode. It is based on empirical data that indicates WAAS degrades timing performance once the survey is compete. There are a lot of SBAS systems out there, so who knows

[time-nuts] Best Chance GPS module

For some unmentioned reason Ublox recommends disabling WAAS for precision time applications. Doesn't make much sense to me --- > Frühauf proposed using satellite dishes on WAAS satellites for improved timing accuracy/stability[1].

Re: [time-nuts] Best Chance GPS module

Hi Simple example: Single sat straight overhead, well compensated by broadcast ionosphere. All survey error in the X direction. Multiple sats all clustered at the horizon. Cluster located on the +X axis. Ionosphere not well modeled over the much longer path. Yes this *is* a bit contrived.

Re: [time-nuts] Best Chance GPS module

On Sun, 4 Dec 2016 09:46:45 -0500 Bob Camp wrote: > It’s possible (but unlikely) to have a single sat in a “perfect” location give > you a better solution than a group of sats in a really crummy location ….. > This is yet another reason for wanting a full sky view. Seeing several

Re: [time-nuts] Best Chance GPS module

Hi > On Dec 4, 2016, at 6:57 AM, MLewis wrote: > > > On 03/12/2016 12:33 PM, Bob Camp wrote: >> For an “antenna challenged” location, the T is the better choice. It is >> simply an update (as the M8Q) of the earlier uBlox parts. The function is >> very similar to the

Re: [time-nuts] Best Chance GPS module

On 03/12/2016 12:33 PM, Bob Camp wrote: For an “antenna challenged” location, the T is the better choice. It is simply an update (as the M8Q) of the earlier uBlox parts. The function is very similar to the earlier parts. You nail down the antenna location (like with duct tape) and put the

Re: [time-nuts] Best Chance GPS module

Hi Lewis, Here is a sample data-point related to processor load, on the RPI 2. Stepping from Idle to full load on 4 cores resulted in a temp rise near the XO of approximately 14 degC, and correspondingly the XO shifted 3.6 PPM. On Sat, Dec 3, 2016 at 10:29 AM, MLewis

Re: [time-nuts] Best Chance GPS module

-Original Message- From: MLewis Sent: Saturday, December 3, 2016 3:29 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best Chance GPS module So much to absorb and learn from what people have responded with. Thanks all

Re: [time-nuts] Best Chance GPS module

Hi > On Dec 3, 2016, at 10:29 AM, MLewis wrote: > > So much to absorb and learn from what people have responded with. > > Thanks all! > > On 01/12/2016 12:01 PM, Chris Albertson wrote: >> OK, now I know what you need. Millisecond level time on the data >> processing

Re: [time-nuts] Best Chance GPS module

HI > On Dec 1, 2016, at 10:54 PM, Gian-Paolo Musumeci wrote: > > > > On Thu, Dec 1, 2016, at 09:01 AM, Chris Albertson wrote: >> The other thing you might look at is NOT using NTP but using PTP. This >> might be a better match to your needs but it requires that you replace

Re: [time-nuts] Best Chance GPS module

On 12/1/16 7:06 PM, Bob Camp wrote: Hi The people doing those site surveys are likely running precision oscillators and worried about errors less than one part in 10 to the 10th Based on tearing apart a number of survey grade GPS boxes …. not so much. The oscillator is hardly in the “super

Re: [time-nuts] Best Chance GPS module

On Thu, Dec 1, 2016, at 09:01 AM, Chris Albertson wrote: > The other thing you might look at is NOT using NTP but using PTP. This > might be a better match to your needs but it requires that you replace > all your network gear with equipment that can make hardware time stamps > on the network

Re: [time-nuts] Best Chance GPS module

Hi > On Dec 1, 2016, at 9:47 PM, Chris Albertson wrote: > > People are mixing precision timing with NTP level or timing. That is way > the conflict in the quotes below. > > If you care about nanoseconds then yes, location comes first. You first > use the GPS to

Re: [time-nuts] Best Chance GPS module

People are mixing precision timing with NTP level or timing. That is way the conflict in the quotes below. If you care about nanoseconds then yes, location comes first. You first use the GPS to do the site survey to determine location from possibly HOURS of data collection from a fixed

Re: [time-nuts] Best Chance GPS module

kb...@n1k.org said: > The navigation solution is something you must have before you can begin to > get a timing solution. That sounds like a 2 step process: where, then when. Does it work that way? I thought you got where and when at the same time - you couldn't get where without also

Re: [time-nuts] Best Chance GPS module

OK, now I know what you need. Millisecond level time on the data processing machine. Let's assume you were able to set up a local NTP server that runs off it's own GPS reference clock. That machine will have an internal clock running at around 10 microsecond error, give or time, Or about 100x

[time-nuts] Best Chance GPS module

You have to read the fine print in the data sheet. "Up to three" can mean 1 or 2. Also if you want SBAS/QZSS corrections, those can also count as systems. Most receivers have limits on which systems can be enabled at the same time. The Ublox is a pain to configure. You have to manually

Re: [time-nuts] Best Chance GPS module

Yes, that's what I thought as well, until I bought and tested one and found out that - in practice - they need an even /better/ set of GPS signals than a simpler position GPS/PPS. Since that's not my experience (even with poor antenna position) I'm curious which unit you were using.

Re: [time-nuts] Best Chance GPS module

On Thu, Dec 1, 2016 at 6:30 AM, David J Taylor < david-tay...@blueyonder.co.uk> wrote: > > Yes, that's what I thought as well, until I bought and tested one and > found out that - in practice - they need an even /better/ set of GPS > signals than a simpler position GPS/PPS. Since that's not my

Re: [time-nuts] Best Chance GPS module

HI GPS depends on a line of sight view to the satellites involved. The time of flight over this path is what gives you the navigation solution. The navigation solution is something you must have before you can begin to get a timing solution. A GPS does indeed go to “no solution” before it

Re: [time-nuts] Best Chance GPS module

From: MLewis I'm hoping a timing GPS module, with their claims of being successful (to the precision I need anyway) on few, or even a single sat. Finger's crossed. == Yes, that's what I thought as well, until I bought and tested one and found out that - in

Re: [time-nuts] Best Chance GPS module

On 30/11/2016 4:23 PM, Bob Camp wrote: 3) Unless you can reasonably expect 4 sat’s in view at all time, don’t bother with setting up a GPS timing system. It will just make you angry with all the issues. I'm hoping a timing GPS module, with their claims of being successful (to the precision I

Re: [time-nuts] Best Chance GPS module

On 30/11/2016 4:23 PM, Gary E. Miller wrote: Yo MLewis! I suggest you take this over to NTPsec:de...@ntpsec.org, or on gpsd:gpsd-us...@nongnu.org Looks interesting. Thanks! On 01/12/2016 1:51 AM, Chris Albertson wrote: First question: How accurate does your local NTP server need to be?

Re: [time-nuts] Best Chance GPS module

Hello, I'm a novice at time issues. I've been gathering info and I think I'm ready to start asking questions. [] A ublox NEO-M8T with an active timing antenna (GPS | GLONASS ?) seems to be my best chance of being successful at my location. Questions: *Is there a more suitable GPS module

Re: [time-nuts] Best Chance GPS module

On 30/11/2016 4:36 PM, Mark Sims wrote: ... V.KEL SIRF=III modules (I paid $15-$20 for three)...They don't do GLONASS. I think I should have GLONASS, to maximize my chances. The NEO M8 is a decent device. I've seen mine tracking over 24 sats. The module that I have has a U.FL antenna

Re: [time-nuts] Best Chance GPS module

First question: How accurate does your local NTP server need to be? If the answer is "a few tens of milliseconds" then you don't need GPS. All yu need is a decent Internet connection. Second. NTP is a VERY light load and certainly does not need to run on a dedicated computer. Any mail

Re: [time-nuts] Best Chance GPS module

Before joining time-nuts I had purchased a QLG1 GPS receiver kit from www.qrp-labs.com. It was $23 plus a few bucks for shipping. I installed the patch antenna as it suited my purposes, but there is the means to omit the patch antenna and use an SMA to go to the antenna of your choice.

Re: [time-nuts] Best Chance GPS module

Hi Most of this is “I have an idea, I can (loosely) connect the idea to big volume, give me *big* piles of money”. Trying to work it out on a technical basis is not going to work very well …. Bob > On Nov 30, 2016, at 6:49 PM, Jay Grizzard > wrote: > > On

Re: [time-nuts] Best Chance GPS module

On 2016-11-30 13:45 , André Esteves wrote: Millimeter accurate GPS in smartphones and self driving cars would result from tiny atomic clocks I saw a different form of this article a month or so back, and for the life of me I can't figure out how having a tiny atomic clock helps GPS accuracy at

Re: [time-nuts] Best Chance GPS module

Millimeter accurate GPS in smartphones and self driving cars would result from tiny atomic clocks -- http://www.nextbigfuture.com/2016/11/millimeter-accurate-gps-in-smartphones.html https://arxiv.org/abs/0707.4624 including energy harvesting, bio-sensing and quantum nanoelectronics. They are

[time-nuts] Best Chance GPS module

I have found that the cheap V.KEL SIRF=III modules (I paid $15-$20 for three) have excellent indoor performance with their built-in patch antenna. They don't do GLONASS. I even get indoor tracking with the module sitting on the ground floor of a 2 story hose with the patch antenna facing

Re: [time-nuts] Best Chance GPS module

Hi A few basics: 1) GPS receivers really can’t / don’t do a lot about multipath. The newer devices with a lot of correlators help a bit, but that’s about it. Simply put - newer is better. 2) Because of near the omnidirectional nature of GPS, antennas don’t do a lot for multipath. They can

Re: [time-nuts] Best Chance GPS module

Yo MLewis! On Wed, 30 Nov 2016 16:11:05 -0500 MLewis wrote: > I'm after a time solution for my personal computer. It looks like I > need: I suggest you take this over to NTPsec: de...@ntpsec.org, or on gpsd: gpsd-us...@nongnu.org They are working on a HOWTO that does

[time-nuts] Best Chance GPS module

(resending as I tried posting in html...) Hello, I'm a novice at time issues. I've been gathering info and I think I'm ready to start asking questions. I'm after a time solution for my personal computer. It looks like I need: *a standalone box to be my own local personal NTP server (so

[time-nuts] Best Chance GPS module

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