[time-nuts] UBLOX LEA-5T Programming?

Graham / KE9H ke9h.graham at gmail.com
Fri Oct 9 12:41:20 EDT 2015


There is a lot of jitter on a GPS 1 PPS output.
You need a big "flywheel" to smooth out the jitter errors.
GPS modules only have room for small flywheels.
--- Graham


On Fri, Oct 9, 2015 at 9:16 AM, Clint Jay <cjaysharp at gmail.com> wrote:

> I am still learning and want to understand, if the PPS is good then why is
> the programmable output bad, as I understand it thus far, the PPS is
> derived from the same clock source or have I got that badly wrong?
>
> On 9 October 2015 at 12:16, Bob Camp <kb8tq at n1k.org> wrote:
>
> > Hi
> >
> > Doing a GPSDO by locking to the awful 10 MHz output from any of these GPS
> > modules
> > is not going to work very well. Given the very long time constants
> > involved in a GPSDO
> > control loop, doing it without code is going to be pretty difficult.
> >
> > A much easier approach:
> >
> > Grab the GPS PPS and a scope. Use it to set the Lucent boxes on
> frequency.
> > Repeat the process
> > once a week.  The direct lock will flop around by (likely many) ppb. Your
> > manual set will probably keep it
> > under 1 ppb for a week.
> >
> > Bob
> >
> > > On Oct 9, 2015, at 1:39 AM, Perry Sandeen via time-nuts <
> > time-nuts at febo.com> wrote:
> > >
> > > Hi,
> > > I have six of the older style (anodized solid aluminum case) Lucent
> > crystal oscillators that I’d like to turn into simple 10 MHZ output
> > GPSDO’s. I have some salvaged HP cases so I can have a linear PS and all
> > other stuff in one package.
> > > I’ve found two different choices of GPS relatively low cost units on
> > Ebay.
> > > One is a LUCENT M12+ GPS Timing Receiver W/100 Hz output  for  $19.99
> > Item 171886538138.
> > > The other is a UBLOX LEA-5T GPS module dev board 1PPS /USB/RS232/ntp
> ser
> > with two 1 PPS outputs for $49.90. Item 251785217093.
> > > IIRC, one output of a Ublox can be set to a 10 MHz.
> > > Can this model be set to have a 10 MHz output and is it easily done
> from
> > a PC? I have no coding ability.
> > > For more money I’d get a simpler phase detector circuit, which is all
> > I’m looking for. For less money I’d have to build more circuitry.
> > > A factor I don’t know is if the ublox is that much better/newer to
> > justify the price difference.
> > > I already have packed away two Oncore units with either a 1 KHz or 10
> > KHz output.
> > > Suggestions welcomed.
> > >  Regards,
> > > Perrier
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>
>
> --
> Clint.
>
> *No trees were harmed in the sending of this mail. However, a large number
> of electrons were greatly inconvenienced.*
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