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1582RE: [dxatlas] Re: Timing Question

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  • Dave
    Nov 18, 2009
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      Hi Dave Baxter- That's the issue and that's the solution. The closer we
      get to a true timing signal the better the app will work. Has Alex
      responded? I haven't any idea how difficult adding a timing routine to
      extract time from a GPS would be, but the true value in the app has to be
      rooted in timing. I prefer the GPS serial-port/USB solution as opposed to a
      receiver into a sound card channel if I had a voice. Some GPS receivers
      boards are fairly inexpensive, but, if one has a GPS already, why not use
      that device and not buy more *stuff*?

      2c worth,

      Dave
      /++++++++++++++++++++++++++++++++/





      -----Original Message-----
      From: dxatlas_group@yahoogroups.com [mailto:dxatlas_group@yahoogroups.com]
      On Behalf Of Dave Baxter
      Sent: Wednesday, November 18, 2009 10:19
      To: dxatlas_group@yahoogroups.com
      Subject: [dxatlas] Re: Timing Question

      Hi Peter (David)

      Just got back from a frustrating on site service visit.


      Yes, I know the Satsignal site, and have had a good exchange with the David
      Taylor there and have successfully got a FreeBSD machine suposedly
      configured to work as needed, from the same distro and version as he used,
      but I've yet to get it to successfully see and work with a Garmin GPS16LVC,
      that has a PPS output (yes, I buffered it to RS232 levels.) The problem I
      have with all that, is I know next to nothing about that level of tweakage
      at the kernel level of any 'nix, that and the 'nix community seems intent on
      flaming anyone who asks questions that they do not see as relavant to their
      latest and greatest distro. (or more relevantly, they do not themselves
      understand.)


      You also it seems found out the hard way what I was told, that the timing
      accuracy of the NMEA sentence delivery from any GPS receiver currently
      available, is not good enough for time keeping to the level we
      need. The eTrex (I have one of the "Yellow" ones too) is otherwise a
      good bit of kit, but useless for any accurate timekeeping.

      Also, like you, I've found that protocols like NTP don't play well with
      mobile internet services. 3G or otherwise.


      VLF Radio time keeping broadcasts could be another way to go, but again, the
      hardware to do the job is prohibitivey expensive, and none of the PC
      software I've found so far that can decode signals like MSF, DCF, WWV etc,
      provide a true full NTP server function. (Some do SNTP, that's about the
      best it gets, and Faros doesnt do SNTP, only NTP it seems.)

      My ISP issues. Well, (long story short) during the business day, there
      seems to be a drastic increase in the network latency getting to anything,
      evne in their own domain/network! If that is not bad enough, it's variable
      one ping to the next, by a wide margin (10's to 100's of mS variation, but
      no packet loss, that is their goal it seems.) Evenings, early mornings and
      weekends, Latency is down to typicaly 25mS.
      During the day, it can go to as much as 500mS, but routinely stretches out
      to 150 to 300mS, depending on the exact time of day, day of week
      etc. Some days are better, some worse. Watching the time accuracy
      plot in Faros, at certain times of day, you can see what looks like the
      effect of someone throwing a switch somewhere. I did some checks, and
      it's not just me, other users of the same ISP are experiencing similar
      effects, though they don't use NTP as we do. It is however messing with
      lots of other systems it seems too.

      As a result, it totaly screws up NTP for any sort of accurate time
      synching, like Faros needs. Hence why I was messing with FreeBSD
      trying to setup a local Stratum 1 server etc. It's getting to the
      state at home now, where I am going to take another serious stab at it, and
      see if I can get it going on an old early pentium laptop, as that is much
      smaller, quieter, and uses less power, than the current desktop I have sort
      of working.

      I'd idealy like to have a "Time Appliance", but commercial units are way
      outside my pocket money range, and like hen's teeth to find too. The
      people who port 'nix etc onto old router hardware are also uninterested in
      helping, from the few exchanges I've had on other forums, and I don't know
      enough to do it myself.

      I did find this... http://scss.com.au/family/andrew/gps/ntp/ But...

      When I asked if he would release a copy of the BINARY (not the propriatry
      TCP stack 'C' code from the compiler) he's gone all silent
      (like no reply, ever!) Pity, as that seems to be what we need. Maybe
      someone else could persuade him to if not release the BINARY, then perhaps
      sell pre-programed (and copy protected) PIC's for such use?


      For now, Faros bumbles along otherwise OK, but when you look at the plots,
      the path charts in the UK afternoon, are often showing a snow storm of white
      "unknown" spots. http://g8kbv.homeip.net:8008/

      As a reception report, most people are interested in the fact that a beacon
      has been realiably heard, not what path it was heard by, I think.


      What I'd like to see long term, is GPS PPS support built into Faros itself,
      that's where it's needed, NTP could still be used if GPS
      reception is not posible, or as a fall back. That alone would make
      Faros most valuable when out portable, or for DXpeditions etc. But of
      course, only Alex can implement that.

      Another option, but would also no doubt be a major undertaking on Alex's
      part, would be to use one channel of the soundcard for the beacons, and
      one channel for a radio code input (WWV, MSF etc) No GPS needed, just
      two RX's, and one of them could be a realy simple SDR like thing.
      (Keeping the audio tones very different, so any crosstalk would be ignored.

      Or, take a pulse train from any of the commonly available miniature VLF
      clock receiver modules, into a com port line somewhere, and use that to set
      Faros's time.


      That's enough from me I suspect. Oh, one more thing. The Javascript I
      use, is more or less that, that is cited as an example to use, if you look
      on the main NCDXF IBP site links. http://faros.ve3sun.com/ is
      where you need to go to start that learning exersize! I make no claims
      for originality on that subject.


      Cheers All.


      Dave Baxter
      G0WBX.


      --- Original Message ---

      My current plan.

      I initially dismissed creating a stratum 0 reference time server - the
      Meinberg PCI card is priced at $3500 in Australia. But ...

      Alex VE3NEA alerted me to the following web site http://time.qnan.org I
      have ordered a Garmin 18x LVS, $100 n Australia, and I will proceed to
      integrate it into my Linux server. On that site there is a reference to
      http://www.satsignal.eu/ntp/index.html which is a fantastic source of
      information relevant to getting Faros a good time signal. I have high hopes
      of having a fantastic Faros installation for propagation study, site and
      antenna comparisons.

      Peter VK4IU


      ------------------------------------

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