[time-nuts] Best counter setting for ADEV?

David davidwhess at gmail.com
Tue Oct 2 16:45:02 EDT 2012

I am sorry if my question was not clear.

Why not phase lock the clock that the pulse per second output is
derived from to GPS time so that the pulse per second output does not
display sawtooth jitter.

I assume this is not done because it is cheaper to report the sawtooth
correction for those who can use it rather than change the GPS
receiver hardware.

On Tue, 2 Oct 2012 12:57:15 -0700, "Tom Van Baak" <tvb at LeapSecond.com>

>All GPSDO "remove that contribution to timing error" by virtue of the quartz "fly-wheel".
>I think David was asking about GPS timing receivers, not full-blown GPSDO.
>Yes, I agree the Thunderbolt is a very nice GPSDO.
>----- Original Message ----- 
>From: "Mark Sims" <holrum at hotmail.com>
>To: <time-nuts at febo.com>
>Sent: Tuesday, October 02, 2012 12:50 PM
>Subject: [time-nuts] Best counter setting for ADEV?
>> No,  the Thunderbolt does it and it works beatutifully.   The GPS receiver clock is derived from the 10 MHz oscillator.  Voila,  no messy sawtooth corrections to deal with.
>> The Thunderbolt is a VERY user/hacker friendly design.  Even if I were silly enough to build my own GPSDO,  I'd still use a Thunderbolt as a base.   It has the EFC dac,  phase comparator, and temperature monitoring already implemented.  Plus no sawtooth correction crap to handle.   You can control the DAC manually and implement your own control loop.   Opps,  siilly me,  been there,  done that.   Lady Heather does have an implementation of an alternate disciplining algorithm in it.
>> ----------------------
>> I assume there is a design compromise that prevents economically phase
>> locking the GPS receiver clock to the GPS signal to remove that
>> contribution to timing error.

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