[time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?

michael taylor mctylr at gmail.com
Thu Dec 13 02:11:44 EST 2007

On Dec 12, 2007 2:32 AM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> Michael
> The analog circuitry for a sigma-delta DAC is attached.
> The input is optically isolated using a high speed low jitter CMOS
> optocoupler (Avago produce an equivalent device) to break low frequency
> ground loops.

I was wondering if the Avago HCPL-9000 or Analog's ADUM1100 iCoupler
would be suitable alternatives to the HCPL-7100.

> Similarly an RF transformer should be used to couple the OCXO output to
> the Digital board breaking another potential low frequency ground loop.

For the RF transformer I am considering a Coilcraft WB1-6(S)L
transformer to decouple the OCXO output.

I want to do some more reading, but I think I'm might have some
questions about DAC input data (from the microprocessor).

Would there be any problems, or benefits to using AHC versus AC logic
family flipflops and the inverting Schmitt triggers?

In regards to the sawtooth correction, I am undecided. If I understand
correctly, even without not addressing it there should be an
improvement over existing public designs (Shera, Miller). If I
remember correctly, you were keen on a software/firmware based
sawtooth approach, if so that might be more flexible and cheaper than
fiddling with a uncalibrated DS1020 delay line.

Thank you,

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