[time-nuts] Rb as source for ADEV?

[Bob Stewart]

Hi Tom,

If I understand you right, the only thing I need from the adev program is the OADEV values and those are the new ADEV?  Here's the plot for the past 24 hours using "0" for bins.  It takes a few seconds to run, doesn't it?  


Thanks for the ideas on what to measure.  I'm going to replace the EFC divider with low temp coeff resistors and do a software bug fix, and hopefully that will be the end of fiddling with this thing and I'll be able to get some really long runs in.


http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png

thanks for all the help,


Bob





>________________________________
> From: Tom Van Baak <tvb at LeapSecond.com>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>Sent: Thursday, February 6, 2014 5:13 PM
>Subject: Re: [time-nuts] Rb as source for ADEV?
> 
>
>Hi Bob,
>
>Short-term measurements like that do a good job using a OCXO and TIC to reveal TIC and GPS resolution limits. It's a useful exercise, but it usually doesn't tell you anything about the OCXO itself.
>
>Long-term measurements like that do a superb job using GPS to measure the long-term stability and frequency drift rate of the OCXO (or Rb). This, because for intervals of days to weeks to months you can't beat GPS as an inexpensive ultimate time/frequency standard. And for those long intervals, the TIC resolution is usually more than enough.
>
>Just collect the raw phase data and raw DAC data. In a few weeks you'll be able to make some really nice plots.
>
>Also consider freezing the DAC for a week (unlocked) and compare that data with your locked data. You can then make plots that look like: http://leapsecond.com/pages/gpsdo/
>
>On Rb -- since you're now a time nut, do not let the Rb warm up at all -- the data get you the first hour or first day will be just as interesting as the data you collect the next month.
>
>On ADEV -- I know the source code calls them adev and oadev, but you should just call it ADEV. No one uses the old back-to-back formula anymore; the overlapping formula is the default. And then plot using the "all" or "many" tau method I mentioned.
>
>/tvb
>
>----- Original Message ----- 
>From: "Bob Stewart" <bob at evoria.net>
>To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
>Sent: Thursday, February 06, 2014 2:23 PM
>Subject: [time-nuts] Rb as source for ADEV?
>
>
>I'm getting a little more familiar with ADEV and OADEV now. With a little help from Tom, I've put together gnuplot scripts and his software to get a decent plot. But, as some time-nuts have pointed out, my measurements are of one part of my system being compared to another. Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long should I let the Rb heat up before starting the test? I'm a bit uncertain about the result of comparing a stable clock of questionable accuracy to an accurate clock of questionable stability. Hopefully I said that right.
>
>thanks,
>
>Bob - AE6RV
>
>
>
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