[time-nuts] More recent information on BG7TBL GPSDO?

[John Laur]

Bob,

Understood regarding NTP; I just thought if it had to be monitored anyway
it could pull double duty. I guess that is not so important.

It appears they are selling well enough to keep up with or otherwise
deplete their supply of surplus OCXOs, so there is probably little
motivation to fix problems. Maybe some additional information will surface
in the future. The design looks simple enough perhaps if the hardware is
documented properly an alternative firmware might be developed - that is a
long shot I know.

John

On Tue, Apr 28, 2015 at 4:47 PM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> The accuracy required by NTP can be met with a <$20 GPS board. It’s much
> easier to simply do a stand alone device than to try to tie everything
> together.
> Fewer ground loops / fewer things to go wrong / easier to keep running.
>
> The frequency offset in the device appears to be a design choice made by
> the
> people running the project. There is no way to find out if they have
> changed their
> design other than buying more devices. That *assumes* that the later
> devices
> have later firmware versions ….
>
> Bob
>
> > On Apr 28, 2015, at 2:57 PM, John Laur <johnlaur at gmail.com> wrote:
> >
> > Hello all. Long time listener; first time caller.
> >
> > I picked up one of the BG7TBL GPSDO units from Ebay, and I am still
> waiting
> > for it to arrive. I understand it has its flaws, but my needs are fairly
> > simple, and I think it will serve.
> >
> > My intent is to use it as a reference which is better than the 0.1ppm
> TCXO
> > in my HF radio, an ANAN-100D (HPSDR architecture); I would like a PPS
> > reference so that I can experiment with timestamped IQ samples; and I
> would
> > like to build an NTP server using a BeagleBone Black. I think this will
> > serve to do these things even if it is not the ideal equipment.
> >
> > I have read I believe all of the previous discussion on this list over
> the
> > past few months including the excellent study by John KE5FX, and I had a
> > few questions to see if there had been any new developments. I understand
> > some may have communicated with the designer as well.
> >
> > Does anyone else have further information on the serial interface? Is the
> > NMEA data directly to/from the U-Blox module or does the internal
> firmware
> > filter/augment it to allow monitoring or tuning of other internal
> > parameters - for instance can one set cable delay? What is its
> suitability
> > for running as a GPS/PPS reference for an NTP server? Any other software
> > suggestions for keeping an eye on it?
> >
> > Second, has the small frequency error identified by John been corrected,
> or
> > is it a problem endemic to the design (I think maybe this was identified
> as
> > a resolution limit of the DAC providing OCXO control voltage; could it be
> > dithered?)
> >
> > As this is my first moderately accurate device in the shack, is my best
> > approach just to put it on the shelf, leave it on for a long time, and
> > trust it? I can see how its easy to begin the slide when there is only
> one
> > clock to stare at skeptically.
> >
> > Thanks,
> > John Laur
> > K5IT
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