[time-nuts] retry: PRS10 has spurious frequencies

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Apr 24 19:05:22 EDT 2007

Brooke Clarke wrote:
> Hi:
> Sorry.  That was a phase plot in the same folder on my computer.  
> Here's my spectrum plot.
> Have Fun,
> Brooke
> http://www.PRC68.com
> http://www.pacificsites.com/~brooke/PRC68COM.shtml
> http://www.precisionclock.com

The 15MHz, 25MHz and 35MHz spurs are possibly produced by the internal 
microprocessor (400ns cycle time clocked at 10MHz).
The lamp oscillator at around 150MHz may also contribute spurs.
The synthesizer may also contribute spurs.
It would have been nice if the lamp excitation oscillator was locked to 
the 10MHz crystal.

The poor close in phase noise performance is probably due to the use of 
saturation as a limiting mechanism in the 10MHz crystal oscillator.
Using cutoff would have been better, however varying the oscillator 
transistor collector voltage with a DAC to control the amplitude is 


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