[time-nuts] Fury Realhamradio listing

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Apr 29 23:38:26 UTC 2007


SAIDJACK at aol.com wrote:
> In a message dated 4/29/2007 04:13:30 Pacific Daylight Time, 
> cfmd at bredband.net writes:
>
>     >Indeed. Three-four transistors and a handfull of caps and
>     resistors. The
>     >Z3801A uses the 10 MHz clock and thus require a x1000
>     interpolation, which is
>     >easy enought to acheive. Look at the HP5335A service manual for
>     further
>     >details. What you do is that you stretch the error-pulse (1-2
>     cycles) by
>     >charging a cap with one current and discharging it with another,
>     the output is
>     >then run into a comparator for the sake of gain. This stretched
>     pulse is then
>     >measured with the coarse clock and voila!
>
> Hi Magnus,
>  
> I respectfully disagree, if it was that easy to get 100ps _accuracy_ 
> and resolution, then the 53132A would have it and not 150ps I would 
> think.
>  
>
> bye,
> Said
Said

Try studying a little history, its been possible to achieve 25 
picosecond accuracy and resolution for over 30 years.
Such resolution is routine in Nuclear instrumentation. State of the art 
nuclear instrumentation strives for subpicosecond resolution and accuracy.

The reason that the 53132A doesn't have resolution and accuracy better 
resolution than 150ps, is that a design choice was made to implement it 
all (counters plus interpolators) in a CMOS chip using the delay of a 
CMOS inverter to set the resolution. This reduces the cost and 
complexity significantly and allows faster cycling of the interpolator 
facilitating continuous operation with zero deadtime between 
measurements. The drawback is reduced resolution and the requirement for 
frequent calibration or the use of a delay lock loop to correct the for 
the CMOS inverter delay tempco.

Bruce




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