[time-nuts] is there a "best bet" advanced hobbyist buildable GPSDOdesign?
bruce.griffiths at xtra.co.nz
Wed Dec 12 03:14:43 EST 2007
Bruce Griffiths wrote:
> michael taylor wrote:
>> You have made similar comments about I believe the same approach in
>> the past. I was wondering if you have ever sketched out a schematic,
>> even if only rough. Perhaps with a few suggested components to try
>> (i.e. DAC, Op-Amp) that would be a good starting point for anyone who
>> wanted to prototype and evaluate the performance of this approach.
>> It is beyond my elementary design abilities to convert your
>> description into a well implemented design on my own, but I would be
>> interested in try to at least see if I could construct an unit using
>> these suggested techniques.
Attached is the circuit for a 1 bit phase detector.
HCMOS should be perfectly adequate given that the flipflop is allowed
several hundred millisec to settle before being read by the microprocessor.
An RF transformer isolated clock shaper should be used to shape the OCXO
output and avoid low frequency ground loops.
You probably want at least a 2 output distribution amplifier (unless
your OCXO has multiple isolated outputs eg FTS1200 OSA8607, some of the
Wenzel OCXOs, etc.) to allow the OCXO output to be used for other
applications as well.
The position of the divider output transition is adjusted by the control
algorithm with respect to the leading edge of the PPS signal so that the
D flipflop Q has a 50% chance of being 1 when read by the
microprocessor. The effective resolution is determined by the jitter of
the leading edge of the PPS pulse.
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