[time-nuts] External clock for Analog to Digital Converter inGPS Rx front-end

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Mar 3 16:29:48 EST 2007


Arnold Tibus wrote:
> Hi,
> HP was using in their 500MHz counter 5345A a noise generator 
> (zener diode with amplifier on PC board 'A8 PLL Multiplier Noise Generator 
> board') to modulate via a varactor and a tank circuit the 10 MHz 
> reference frequency coming from the ocxo 10811A. 
> "4-126, As the erratic changes in noise affect CR12's capacitance, the 
> phase of the 10 MHz signal shifts rapidly. The result ia a 500 MHz time base 
> signal that is phase modulated so rapidly and erratically that it cannot be 
> harmonically related to any input signal."
> Intersting technique, easy to follow.
> Is that what was searched, would such a circuit help? 
> The manual is freely available via the net as .pdf. 
> Perhaps that board, cannibalized from an old counter, could be used...
> I think it is necessary for TIC to get statistically correct intermediate 
> counts.
>
> cheers,
> Arnold, DK2WT
>
>   
Arnold

Circuit is fine for the application it was designed for.
However for measurement purposes accurately calibrating the phase noise 
spectrum it generates poses some interesting challenges.

Bruce



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