[time-nuts] GPS message jitter (was GPS for Nixie Clock)

[Scott Stobbe]

Bob, Thanks for the nudge towards Ublox. USB was a bit of blue sky thinking.

I took a look at the LEA-M8F module which by default includes a VCTCXO.
Will also take care of disciplining an (VC)OCXO provided a DAC is included.
What was interesting to me is you can "exchange" time it, copied from the HW
Integration Manual
<https://www.u-blox.com/sites/default/files/products/documents/LEA-M8F_HIM_%28UBX-14000034%29.pdf>

*1.6.3 FREQ_PHASE_IN0 / EXINT0, FREQ_PHASE_IN1 / EXTINT1 These two
frequency/phase inputs are provided for connecting an external source of
phase (pulse stream) or frequency reference into the module. The pulse
stream can be derived from a frequency reference or external
synchronization source. The module will measure and report the phase or
frequency offset of this input with respect to the current synchronization
source and optionally steer the related oscillator to bring the externally
derived pulses into alignment*


On Mon, Jul 18, 2016 at 7:28 PM, Bob Stewart <bob at evoria.net> wrote:

> Interestingly enough, the Ublox LEA series of timing receivers has a USB
> port which you can connect directly to a USB cable.  Of course you want to
> use an ESD device, etc.
> Bob
>  -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>       From: jimlux <jimlux at earthlink.net>
>  To: time-nuts at febo.com
>  Sent: Monday, July 18, 2016 5:46 PM
>  Subject: Re: [time-nuts] GPS message jitter (was GPS for Nixie Clock)
>
> On 7/18/16 1:44 PM, Scott Stobbe wrote:
> > Well, I suppose in the case of USB, the host hardware (consumer PC) is
> not
> > going to have any special hardware. But, if a gps receiver implements a
> USB
> > interface, in addition to standard NEMA data, it could also report the
> > phase and frequency error of your USB clock (since it has to recover it
> > anyways to get the usb data).
>
> The USB interface timing is going to be buried deep, deep inside some
> microcontroller or ASIC. Imagine a FTDI part, for instance.  I can't
> imagine a GPS mfr caring enough about this to spend any money on trying
> to figure out how to do it.
>
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