Author Topic: GPS Disciplined Oscillator review and teardown  (Read 1550 times)

Andy Brown

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GPS Disciplined Oscillator review and teardown
« on: November 12, 2016, 02:20:45 am »
Quite some time ago I bought a GPS Disciplined Oscillator (GPSDO) on ebay to calibrate my Nanocounter frequency counter project.



I've now got around to reviewing it and taking it apart to see what's inside. Click here to read the article.
It's worse than that, it's physics Jim!

aNTOn hendra

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Re: GPS Disciplined Oscillator review and teardown
« Reply #1 on: November 29, 2016, 06:03:20 pm »
Do You know is this GPSDO has a PLL or FLL control ?
one of classic problem with FLL is like BG7TL GPSDO is not "accurate" freq generated I believe come from rounding in digital counting thats why PLL more desirable but PLL has another problem about loop filter time constant if it use analog loop filter we deal with capacitor imperfection etc. if this Symetricom board has PLL and can control the time loop constant in digital to match the OCXO drift that will be wonderful.
 

Andy Brown

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Re: GPS Disciplined Oscillator review and teardown
« Reply #2 on: December 14, 2016, 02:12:54 pm »
Do You know is this GPSDO has a PLL or FLL control ?
one of classic problem with FLL is like BG7TL GPSDO is not "accurate" freq generated I believe come from rounding in digital counting thats why PLL more desirable but PLL has another problem about loop filter time constant if it use analog loop filter we deal with capacitor imperfection etc. if this Symetricom board has PLL and can control the time loop constant in digital to match the OCXO drift that will be wonderful.

The status command reports the PLL mode - you can see it in the main article. So it would appear that there is a PLL inside.
It's worse than that, it's physics Jim!