[time-nuts] time-nuts Digest, Vol 165, Issue 48

AC0XU (Jim) James.Schatzman at ac0xu.com
Wed Apr 25 07:51:56 EDT 2018


Gary-

Interesting. The TICC is spec'ed to have a 10e-10 AD floor at 1 sec. Your measurement is slightly better than the spec. How can we know whether you are measuring the test source  (JL GPSTLXO) or the stability of the TICC itself?

Jim



At 03:10 AM 4/25/2018, you wrote:
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>Today's Topics:
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>   1. Re: Cheap jitter measurements (Gary E. Miller)
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>----------------------------------------------------------------------
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>Message: 1
>Date: Tue, 24 Apr 2018 20:45:08 -0700
>From: "Gary E. Miller" <gem at rellim.com>
>To: time-nuts <time-nuts at febo.com>
>Subject: Re: [time-nuts] Cheap jitter measurements
>Message-ID: <20180424204508.5794f374 at spidey.rellim.com>
>Content-Type: text/plain; charset="utf-8"
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>Time-nuts!
>
>I went ahead and bought the TAPR-TICC, it is a very impressive
>instrument.  For this setup it is combined with a Jackson Labs
>GPSTLXO as the 10MHz reference.  The JL is a GPS disciplined temperature
>compensated crystal oscillator.
>
>The first setup uses the TAPR-TICC in Period mode, outputting the PPS
>period individually for channel A and channel B.
>
>Channel A is the PPS of a plain u-blox NEO-M8N.  Channel B is the
>PPS of the JL GPSTLXO.
>
>Simple to get the cycle times from the USB serial port.
>
>Then I grabbed a copy of the easy to use Python Allantools.
>    https://github.com/aewallin/allantools
>
>A little coding later and there are nice plots.  They were compared to
>the output of tvb's adev.c program.  Results are similar.
>
>Results are attached.  gps.png is the plain NEO-M8N.  GPSTLXO is the
>JL part.
>
>gps.png looks as expected.  GPSTLXO.png shows the quality of the JL part,
>but does have some odd divots in the plot.  Maybe artifacts of using the
>PPS derived from the reference 10MHz?  Or an artifact of the 10e6 divider?
>
>There are adev's of Rb standards here: http://www.ke5fx.com/rb.htm
>
>My guess is that the oadev at 1s would be about 50x better with
>a Rubidium?  But similar at 10k seconds?
>
>Comments?
>
>RGDS
>GARY
>---------------------------------------------------------------------------
>Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>        gem at rellim.com  Tel:+1 541 382 8588
>
>            Veritas liberabit vos. -- Quid est veritas?
>    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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