[time-nuts] PicTic Data

[Stanley Reynolds]

Thanks for looking at my data that was what I was fishing for all along :-)

I was looking at the article: 

"A Small Dual Mixer Time Difference (DMTD) Clock Measuring System W.J. Riley " 
Richard posted
 
And thinking it would be nice to do the DSS and Mixer boards to go with the 
pictic II.
 
Or changing the Pictic II to use the Acam TDC GP2 Time to Digital Converter; 2 
channel w/65 ps resolution now under $30. as Bruce suggested a while back.
 
My wants sure exceed my cans ;-)
 
Stanley
 


----- Original Message ----
From: John Miles <jmiles at pop.net>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sat, August 14, 2010 11:25:44 PM
Subject: Re: [time-nuts] PicTic Data


> John glad you are getting good results and have something to
> compare to. Back to
> me who doesn't have any knowns but lots of guessing. Attached is
> a run with a
> box cover over the pictic, run is shorter ~ 800 seconds but the
> box does look
> like it helps.
> I need to do a lot more testing but sometimes I just get excited :-)

I imported your .txt file alongside the traces I captured.  Assuming it was
taken with 1 Hz on both START and STOP, it looks like the attached.

You're getting the exact sort of results that I see if I feed both the START
and STOP inputs at 1 Hz.  My guess is that the onboard oscillator limits the
performance in that case, since it has a lot of time to drift during the
measurement if the two pulses occur close to 1 second apart.  Even the 5370B
looks much worse if driven with 1 Hz on both inputs than it does with 1 Hz
at START and 10 MHz at STOP.

So I think you're basically up and running OK.  When I get around to trying
a better clock, I'll also go back and see if the 1-pps x2 performance
improves.

It would be great if the next spin of the board could include sine-to-CMOS
shapers for the input channels as well as an external clock input, for
people who are working directly with RF signals as opposed to 1-pps.

-- john, KE5FX


> ----- Original Message ----
> From: John Miles <jmiles at pop.net>
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Sent: Sat, August 14, 2010 10:19:46 PM
> Subject: Re: [time-nuts] PicTic Data
>
> A few preliminary measurements here (I'm working on getting some software
> support together):
> http://www.ke5fx.com/pictic.htm
>
> -- john, KE5FX
>
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> > Behalf Of Stanley Reynolds
> > Sent: Saturday, August 14, 2010 7:12 PM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] PicTic Data
> >
> >
> >
> >
> > My guess as to what the data may indicate is performance of the
> > 10 Mhz 20PPM
> > PICTIC internal oscillator, need to repeat test with precision
> > 10Mhz and auto
> > calibrate off. Fatness of the line/width maybe PICTIC error. Note
> > graph seems to
> > show me leaving the room and returning via the outside door. Not
> > sure what the
> > ~100 sec oscillations are, need to check a/c cycle time.
> >
> > Stanley
> >
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