HELP:making a 10Mhz gps reference oscillator

Discussion in 'General Electronics Chat' started by hamopp, Jun 2, 2013.

  1. hamopp

    Thread Starter Active Member

    May 13, 2009
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    Hi all
    I have been given a FASTRAX UP501 gps with built in ant
    it has 1pps output.
    Datasheet can be found here
    www.anglia.com/fastrax/datasheets/UP501.pdf‎

    I have also got a Efratom 105243-003 10Mhz ocxo

    I would like to make a 10mhz reference to use on
    some of my test equipment, but not been able to
    find any circuits for making one, anyone able to help?

    Regards
    hamopp
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Hamopp,

    The Fastrax module will only generate a 1pps signal once it registers a 3D location. Therefore, an antenna and access to a signal will be needed.
     
  3. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Google for "DIY GPS disciplined 10MHz source" there are a lot of projects out there on the HAM sites.

    Generally they are using a microcontroller to do the measurement and filtering for the 1Hz->10MHz PLL task.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Last edited: Jun 3, 2013
  5. hamopp

    Thread Starter Active Member

    May 13, 2009
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    This unit has a built in antenna and can have access to a signal from my qth
    hamopp
     
  6. hamopp

    Thread Starter Active Member

    May 13, 2009
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    Hi
    Found one of these: Navman jupiter T Tu60 GPS Kit 1pps 10khz GPS Module.
    would this be a better one to use ??
    hamopp
     
    Last edited: Jun 3, 2013
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That's just a xtal in a box, with a +/- 100 PPM error. Hamopp is talking about making something >1000 times more accurate than that. :)

    The Jupiter GPS has a 10kHz output that makes it easier to directly PLL up to 10MHz. But if you are using a microcontroller you don't need to hardware PLL, you can get a much better result with software PPL systems from any GPS with a standard 1 PPS pulse.
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The one I used was from General Instruments and it is accurate to 1 ppm (six decimal places). They are around and don't cost all that much. They are hybrids which have the temp compensation built in.

    20 ppm


    http://www.ebay.com/itm/10pcs-100MH...100?pt=LH_DefaultDomain_0&hash=item1e777a9104


    Under 1 ppm:

    http://www.ebay.com/itm/NEW-10MHz-O...al_Components_Supplies_ET&hash=item484422d3e2
     
    Last edited: Jun 4, 2013
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The first link is just a typical xtal oscillator at +/-20PPM, which many xtals will do, but being an oscillator it can't be cap trimmed to better than the 20 PPM like the xtal. So to me, that's worse than a xtal.

    You rsecond link is interesting (thanks!) but is an OCXO (oven controlled xtal oscillator). Normally these are >$80 for a new one, the one in your link is $27 for "surplus new-old stock" etc. These still need calibrating, and still drift (especially if it is a cheap brand that has not been pre-aged) and worst still require 100mA or more for the oven heaters.

    So even to get it very precise still needs to be calibrated against a GPS etc. Hamopp says he already has an OCXO, and needed the GPS to discipline it.

    To Hamopp; do you have experience with microcontrollers? Most fo the GPS modules now can be set to change the output frequency via serial commands. I set my Ublox GPS to make the output 100kHz for some testing, and it worked fine.
     
    bug13 likes this.
  10. hamopp

    Thread Starter Active Member

    May 13, 2009
    68
    1
    Hi all
    Thanks for all the comments, all noted.
    I have since bought the Navman jupiter T Tu60 GPS Kit 1pps 10khz GPS Module
    from China ($65) about £42.

    This has a 1pps and 10Khz output, i have found a few circuits on the net that use
    the 10Khz to a PLL, which i believe is a better way to go.

    The other thing that i would like to have is multi 10Mhz outputs (1 to 2v pk-pk)
    and a few 1Mhz outputs
    (1 to 2v pk-pk).

    No i don't have experience with microcontrollers (i don't code)

    What about this one:

    http://electronics-diy.com/electronic_schematic.php?id=941

    Regards
    hamopp
     
    Last edited: Jun 5, 2013
  11. Meixner

    Member

    Sep 26, 2011
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    Search on EBAY for " 10 Mhz rubidium frequency standard " you will find units for < $100.
     
  12. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Hi, yeah if you don't have microcontroller programming ability then the 10kHz-10MHz hardware PLL will be your best shot. It won't be quite as good as a software solution.

    This schematic from the link you posted shows the block diagram;

    [​IMG]

    The first blocks are the 10MHz frequency dividers (the 74LS390 IC), you can see ho outputs 5MHz signal from one tap in that IC, the next tap (pin 9) is after a /5 unit so will be your desired 1MHz output tap. :)

    You could even put a rotary selector switch on a few of those taps and choose between 5/1/200k/100k/10k outputs etc.
     
  13. hamopp

    Thread Starter Active Member

    May 13, 2009
    68
    1
    Hi
    THE_RB, Would you be able to help with a software solution ?.

    I would like to have a few (maybe 3) 10Mhz outputs (1 to 2v pk-pk)
    and a few (maybe 3) 1Mhz outputs (1 to 2v pk-pk).

    This would be used as a freq standard for my Racal freq counter,
    rf signal generator and anything else that needs a good gps freq
    standard.

    Regards
    hamopp

     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    There are quite a few documented projects by the HAM guys.

    This one is good;
    http://ve2zaz.net/GPS_Std/GPS_Std.htm

    There are a lot of good pages on the net. Also check the "GPS disciplined rubidium oscillators" as they are basically the same thing and the microcontroller code will work equally well with an OCXO (as they both have voltage controlled freq trimming).
     
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