[ntp:questions] Is there an easier way to hook a GPS clock to NTP or a free shortwave audio line level out?

Nate Homier ntp at universal-mechanism.org
Wed Dec 16 17:27:39 UTC 2015


I emailed learn.adafruit.com with my questions.  Looks good.  I'll have 
to wait to hear back from the http://ava.upuaut.net people too before I 
decide.  Lots of good stuff posted.  Thanks Nate.

On 12/16/2015 18:20, dan at drown.org wrote:
> Adafruit is another supplier you can look at:
> https://learn.adafruit.com/adafruit-ultimate-gps-hat-for-raspberry-pi
>
> There's four products on that page:
> The GPS board for the Raspberry PI, the external Antenna, the antenna
> adapter cable, and the coin cell battery.
>
> The coin cell battery is optional, but I'd recommend the other three.
>  The external antenna and adapter is actually optional as well, but
> it'll result in a stronger signal.
>
> The Geaux Robot Case looks ok, but I don't know if there's room
> between the top and the hat.  I'm guessing that's why they have the
> stacking header listed, as an extension.
>
> Do you already have a PI B+?
>
> Quoting Nate Homier <ntp at universal-mechanism.org>:
>> OK!  I'm going with the Raspberry PI B+ with a plug in GPS receiver. 
>> So on the http://ava.upuaut.net store it list the GPS receiver then  
>> down below it list the nine related products.  So if I understand  
>> right I want the B+ version.  The case looks cool and I just need  the 
>> case and the 25mm M3 Standoff Kit for Geaux Robot Case.  What  about 
>> Stacking header kit for Raspberry Pi+ do I need it and do I  need this 
>> one too, 11mm Stand off kit for Raspberry Pi+?  Which of  those three 
>> GPS antennas do I need and what's the difference between  them.
>>
>> On 12/16/2015 1:20, Mike Cook wrote:
>>> Hi Nate,
>>>
>>>  I think you can forget about using your radio as the E1’s lowest
>>> band is from 100KHz and WWVB which is what you want for timing is 
>>> on
>>> 60KHz. I don’t know of any FM station time decoders.
>>>
>>> After that cold shower, the options are limitless wth quite a 
>>> number
>>> entailing gluing small bits.
>>> I have gone the way of gluing bits and I have a lot of them.
>>>
>>> Your stats are are bad, due probably to the >2:1 asymmetry in
>>> upload/download rates on 4G plus latency on the WIFI. You might 
>>> also
>>> be compounding that with power saving on your system though you 
>>> don’t
>>> say how that is configured.
>>>
>>> If you want low budget, and have no better internet access you 
>>> might
>>> get by with a cheap PCI-E GPS such as Ublox GPS B39 PCI-5S-1-500 at 
>>> <
>>> $10 delivered from the auction site, coupled to a mini PCI-E to 
>>> PCI-E
>>> adapter (ex 181622523046 on the same site) for $5 delivered, an 
>>> active
>>> SMA antenna with say 5m of cable , another $10 plus
>>> an SMA pigtail to replace the RP-SMA at a couple of $ 
>>> (ex.281842153844).
>>> Link all that up and you will have an NMEA ref clock (over what 
>>> will
>>> look like a USB serial port to your OS) that should give you low ms
>>> accuracy and stability for less than $50.
>>> The GPS receiver seems to have a 4Hz update rate which is not 
>>> useful,
>>> but it can be reconfigured to 1Hz (see
>>>
>>> 
>>> <http://emerythacks.blogspot.fr/2013/01/u-blox-pci-5s-cheap-gps-module-for-your.html>
>>> ) with Ublox’s U-Center free software. That runs on windows only, 
>>> but
>>> should run under wine in linux or maybe you can dual boot your 
>>> system
>>> or ask a friend.
>>>
>>> I prefer to have my time servers independent of application 
>>> workload
>>> , so I have many minis dedicated to that.
>>> A good cheap one is a Raspberry PI B+ with a plug in GPS receiver
>>> such as
>>>
>>> 
>>> <http://ava.upuaut.net/store/index.php?route=product/product&path=59_60&product_id=117>
>>> which has few bits and only one connector to solder. If you ask
>>> nicely, the seller will probably do it for you. If you add a usb 
>>> wifi
>>> dongle you won’t need cabling but you get better latency with 
>>> cable,
>>> so I would use that as you have ethernet on your box. The 
>>> advantages
>>> here are that you can leave it on all the time, and it will have 
>>> 1PPS
>>> ref clock, so you have microsecond accuracy and stability. Well I 
>>> do
>>> with that config.  With a case, antenna etc I think you can get a
>>> clean setup for < $150.
>>>
>>> Of course you can do cheaper with bits. Take your choice.
>>>
>>> Caveat:
>>>  As you have a crappy internet connection , even with a really
>>> accurate inboard or external time source, it will be only ONE. This 
>>> is
>>> not a good config . You really need a minimum of 3 .
>>> How much would a proper internet connection cost you?
>>>
>>> You seem to be between a rock and a hard place.
>>>
>>> Regards,
>>> Mike
>>>
>>>> Le 13 déc. 2015 à 17:06, Nate Homier <ntp at universal-mechanism.org> 
>>>> a écrit :
>>>>
>>>> I am using a system76.com Wild Dog Pro desktop computer running  
>>>> Ubuntu 15.10, I bought it in December 2015.  It has no serial  port. 
>>>> I have a Shortwave radio if that will work to hook up to  NTP.  
>>>> Researching the net reveals many howto for hooking up GPS  OEM 
>>>> radios.  This usually involves soldering, cutting and working  with 
>>>> little tiny things, all of which I am terrible at.  I have  heard of 
>>>> GPS radios that plug into your PCI-E slot, now that  sounds cool, 
>>>> but pricey.
>>>>
>>>> Does anybody have any recommendation as to how I can turn myself  
>>>> into an accurate stratum 0 or 1 client, I am not interested in being
>>>
>>> Stratum 0 is the reference clock, Atomic, GPS, WWVB or whatever  . 
>>> It
>>> is what makes an NTP source Stratum 1, so if you have a ref clock 
>>> then
>>> your box will  default to stratum 1 while the ref clock is 
>>> reachable.
>>> You can fudge stratum levels in the config, but it is unusual 
>>> outside
>>> testing.
>>>
>>>> a server.  In case your wondering why, I don't know why, I do have 
>>>> an official diagnosis of OCD, that might explain it.  Not accurate  
>>>> time bothers me a lot.
>>>>
>>>> I have an Eton E1 HF receiver that keeps it's clock accurate via  
>>>> the HF time bands, but not the LF band, strange, on the other hand  
>>>> your guaranteed to get an HF signal worldwide as opposed to LF.   It 
>>>> also has an audio line out and does anybody have any experience  
>>>> with line level audio for time keeping.  Maybe I should start  there 
>>>> before forking over the cash for some project I can't finish.
>>>>
>>>> Here's what I'm willing to do.
>>>>
>>>> Do the shortwave radio thing first.  Free and what I learn from it 
>>>> I can apply to below.
>>>>
>>>> Buy an PCI-E port serial card, one that you guys tell me to buy, 
>>>> budget $75
>>>> Buy an GPS PCI-E card or external device.  I can't give you a  
>>>> figure for what I'm willing to pay because I have no idea what  they 
>>>> cost.
>>>>
>>>> Just doing this for fun.  Love NTP.
>>>>
>>>> Currently I am getting Internet through my Verizon Samsung Galaxy  
>>>> S6 Edge WiFi hotspot.  -102 dBm and 38 asu signal, poor signal for  
>>>> 4G LTE.  Once I get up in the morning I turn off the Internet at  
>>>> about 11 am and the computer won't see a connection again until 8  
>>>> or 9 pm.  So NTP is only connected during the night when I'm  
>>>> sleeping.  Anybody know how I can keep track of clock drift when  
>>>> NTP gets woken up at night, be interesting to see how accurate the  
>>>> motherboard is.
>>>>
>>>
>>> NTP’s drift file will give you that info , though your connection
>>> looks so bad that it may not be that good a figure. You really need
>>> stable sources for to enable NTP to calculate it.
>>>
>>>> My current NTP stats.
>>>>
>>>> First one is from peer.awk
>>>>
>>>> ident                       cnt  mean     rms     max      delay   
>>>> dist     disp
>>>>
>>>> 
>>>> ==========================================================================
>>>> 208.75.89.4                 21   30.724   60.139  161.716  103.967 
>>>> 989.601  149.718
>>>> 2604:a880:800:10::bc:c00d   19    8.736   16.624   32.476  134.039 
>>>> 499.117   42.186
>>>> 50.116.38.157               18   19.069   23.196   46.512  141.819 
>>>> 495.233   44.446
>>>> 2001:67c:1560:8003::c7      17   -2.631   18.085   41.863  204.340 
>>>> 173.570   23.222
>>>> 104.41.150.68               18   37.286   26.949   50.019  147.775 
>>>> 174.419   39.181
>>>>
>>>>
>>>> nate at frontier:~$ ntpq -p
>>>>    remote           refid      st t when poll reach   delay    
>>>> offset  jitter
>>>>
>>>> 
>>>> ==============================================================================
>>>> +deekayen.net    152.2.133.52     2 u  554 1024  377  135.533   
>>>> -23.196  82.525
>>>> *time.tritn.com  198.60.22.240    2 u  531 1024  377   82.637   
>>>> -26.905  62.751
>>>> +2604:a880:800:1 131.234.137.24   2 u  592 1024  377  149.243   
>>>> -23.740  63.528
>>>> +104.41.150.68   129.6.15.30      2 u 1007 1024  377  109.755     
>>>> 5.461  87.911
>>>> +golem.canonical 170.224.124.217  2 u  488 1024  377  182.265   
>>>> -44.495 158.015
>>>>
>>>> Sincerely Nate.


More information about the questions mailing list