[time-nuts] LEA-M8T

ken hartman ken at hartmans.org
Thu Apr 7 15:30:26 UTC 2016


What Bob Camp said about PRECISION navigation and as it applies to
precision time is true. Do not mix different constellations. There is
direct evidence.



On Thu, Apr 7, 2016 at 9:43 AM, Björn <bg at lysator.liu.se> wrote:

> For navigation more measurements have always been prefered - that is use
> as many GNSS systems as all your receicers support.
>
> That should be true also for common view timing.
>
> --
>        Björn
>
> <div>-------- Originalmeddelande --------</div><div>Från: Bob Camp <
> kb8tq at n1k.org> </div><div>Datum:2016-04-07  18:41  (GMT+07:00)
> </div><div>Till: Bob Stewart <bob at evoria.net>, Discussion of precise time
> and frequency measurement <time-nuts at febo.com> </div><div>Rubrik: Re:
> [time-nuts] LEA-M8T </div><div>
> </div>Hi
>
> Indeed, if you have not turned off the other systems for timing, you will
> have issues. Even for
> precision navigation, you need to turn them off. Until the European system
> goes up, there will
> not ba a coordinated approach between any two of the systems. Right now
> they each make their
> own assumptions and their own definitions. If you are driving a car down
> the road, that’s not a
> big deal. If you are trying to do TimeNuts stuff … A one meter delta is a
> big deal for timing. A “few”
> nanoseconds (say >10) is also a big deal.
>
> Bob
>
>
> > On Apr 6, 2016, at 9:39 PM, Bob Stewart <bob at evoria.net> wrote:
> >
> > Hi Logan,
> >
> > I seem to remember Bob Camp mentioning that you can't have multiple
> satellite sources in the mix, because the other satellites are inferior to
> the GPS sats in timing.  Maybe Bob or someone could address this.  I would
> love to discover that I've set something wrong in all the many, many data
> structures.
> >
> > Bob
> >
> >
> > --------------------------------------------
> > On Wed, 4/6/16, Logan Cummings <logan.cummings at gmail.com> wrote:
> >
> > Subject: Re: [time-nuts] LEA-M8T
> > To: "Bob Stewart" <bob at evoria.net>, "Discussion of precise time and
> frequency measurement" <time-nuts at febo.com>
> > Date: Wednesday, April 6, 2016, 8:18 PM
> >
> > Hi
> > Bob,
> >     Can't speak to
> > jitter accuracy but the M8 series is definitely not the same
> > receiver in the 6 series. As you probably know, M8
> > introduced multi-GNSS support so in addition to GPS you have
> > Beidou and Glonass satellites.
> >       At work we've had some gnashing of
> > teeth about the wider filter passband requirements for
> > multi-GNSS support since we're operating in a noisy
> > environment, but I have nothing further on degraded
> > performance when using only GPS.
> >      Would be interesting to let
> > it have all the constellations and see what
> > happens.
> > -Logan
> > On Wed, Apr 6, 2016 at
> > 10:04 AM, Bob Stewart <bob at evoria.net>
> > wrote:
> > I
> > recently bought a number of LEA-M8T receivers and I have to
> > say that I am unimpressed, so far.  They don't survey
> > to the same reported accuracy as the LEA-6T in the same
> > amount of time.  They certainly aren't better in the
> > jitter after sawtooth correction.  So, have I managed to
> > overlook some new field, or are they just not the same
> > receiver as the 6T?  I did shut all sats off except GPS
> > sats.
> >
> >
> >
> > Bob - AE6RV
> >
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