[time-nuts] Question for any HP105 owners

[Mark Spencer]

To expand upon my original email, the averging time was one second when I used the HP 5370B, .8 of a second when I used the Tek Scope as a time interval counter.   

I've also collected data with averging times as low as .1 of a second using the 5370B.   When looking at the results for tau of 100 seconds or more the results are more or less the same for me.    

For tau of less than 100 seconds it appears the relative merits of the two instruments, combined with shorter averging times can change the resuls some what and I don't have as much confidence in the results at lower tau.

--- On Tue, 8/30/11, Tom Van Baak <tvb at LeapSecond.com> wrote:

> From: Tom Van Baak <tvb at LeapSecond.com>
> Subject: Re: [time-nuts] Question for any HP105 owners
> To: "'Discussion of precise time and frequency measurement'" <time-nuts at febo.com>
> Received: Tuesday, August 30, 2011, 12:56 PM
> Hi Paul,
> 
> Right, the averaging time, tau, is critical when quoting
> ADEV
> numbers. In fact, the key feature of any ADEV plot is
> seeing
> how stability changes as a function of tau. But Mark
> mentioned
> "at 100 seconds" so that allowed me to compare his single
> ADEV number against the tau 100 second column of a full
> log-log plot.
> 
> Your data looks odd to me. Sample rate, or bandwidth, can
> have a noticeable effect for short tau but I would expect
> that
> by the time you're all the way out to tau 100 s that the
> points
> would be about the same. Instead in your case they differ
> by
> an order of magnitude.
> 
> Can you zip up the raw 5370 data for each run and email it
> to me? That will help me spot the problem.
> 
> Thanks,
> /tvb
> 
> ----- Original Message ----- 
> From: "Paul A. Cianciolo" <paulc at snet.net>
> To: "'Tom Van Baak'" <tvb at leapsecond.com>;
> "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Sent: Tuesday, August 30, 2011 8:24 AM
> Subject: RE: [time-nuts] Question for any HP105 owners
> 
> 
> > Tom,
> >
> > Is there an assumption that is normally made when
> referring to ADEV.
> >
> > For example I looked at your image and see that you
> the chart begins at  .1
> > seconds, so I am assuming that the sample rate was .1
> sec to acquire these
> > numbers.
> > But Mark  does not specify a sample time in his
> ADEV number.
> >
> > Right now after I am testing a Rakon double oven
> oscillator and I see the
> > following.
> > Using a HP5370, z3801 reference for both the LO and
> the ref input on HP
> >
> > Using .1 sec sample rate:
> >
> > 4.18 x 10 -11  @ 1sec
> > 7.04 x 10 -12  @ 10 sec
> > 1.11 x 10 -11 @  100  sec.
> >
> > Using a 1 second sample rate
> >
> > 3.85 x 10 -11 @ 1sec
> > 4.01 x 10 -12 @ 10 sec.
> > 9.60 x 10 -13 @ 100 sec.
> >
> > This oscillator has been running now for barely 20
> hours.  The z3801a has
> > been running for about a year
> >
> > Am I doing something wrong?
> >
> > Thank you
> >
> >
> >
> > Paul A. Cianciolo
> > W1VLF
> > http://www.rescueelectronics.com/
> > Our business computer network is  powered
> exclusively by solar and wind
> > power.
> > Converting Photons to Electrons for over 20 years
> 
> Does it really take 20 years to do the conversion? ;-)
> 
> 
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