[time-nuts] PicTic Data

Bob Camp lists at rtty.us
Sun Aug 15 12:53:02 UTC 2010


Hi

If I remember correctly, the inboard clock was chosen to be a "good source of noise" during the calibration process. It's certainly not a high stability clock.

Bob



On Aug 15, 2010, at 12:25 AM, "John Miles" <jmiles at pop.net> wrote:

> 
>> 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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>> 
>> 
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> <capture2_freq.gif>
> <capture2_adev.gif>
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