[time-nuts] Fury Realhamradio listing

SAIDJACK at aol.com SAIDJACK at aol.com
Sun Apr 29 16:11:16 EDT 2007


 
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.
 
Also, the PRS10 Stanford Rubiudium would have better than 1ns resolution  for 
time-tagging. I think they actually do resolve better than 1ns, but don't  
use it.
 
On the Z3801A I am still seeing folks speculate that it has 100ps  resolution 
just because that's what they print out as the averaged value. Does  anyone 
have schematics to confirm this?
 
The user manual even states that the number is an averaged version of  the 
true Time Interval. Same for the 58503B.
 
There is an easy way to verify this for anyone with access to a Z3801A or  
58503B:
 
Both units use the VP Oncore, speced at 31ns RMS sawtooth 1PPS jitter  and at 
around 100ns peak to peak jitter.
 
So if the Time Intervall circuit was not doing any filtering (which we know  
it does, since the HP manuals state that it does), then the Standard Deviation 
 of the PTIM:SYNC:TINT? query results should have a peak to peak  result 
slightly worse than 100ns, and a standard deviation of around 30ns.  Of course we 
would have to add the OCXO noise and the quantization error on  top of these 
values.
 
Has anyone done any analysis on the TI values that the Z3801A gives  (besides 
GPSCon, which gives about 50ns pk to pk and 10+ns Standard  Deviation for 
most Z3801A'a)?
 
bye,
Said



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