[time-nuts] Advantages of GNSS ???

Tue Jul 9 17:30:40 UTC 2019

RobertThat was my wrong take, since as long as I have messed with timing GPS receivers the difference was price and the fact that saw tooth data was present in hardware. Juerg did his first  M12/Dallas/Maxim in 2004 driving a PRS 10 only replacing it when he bought a Tbolt through TARP.Working 10 years ago with Richard Mc Corkle his GPS MAX used also a PIC to read M12 data adding it up for the time constant and adding the sum to his filter calculation.
He also did a PIC for me using the D/M chip.Since something happened to Richard I set out to do a board to be used for our GPSDO.  Tests did not show ant improvements.
Did a Furuno board without saw tooth because it is only 4 nsec. Works great. In all cases the PIC also generated the survey command in order to work without a computer. The Furuno T does on power up an automatic survey. The N version also works great and is available at Berklin for 1/3 the price of T but does not survey. Only other one also with 1 pps. Looks like Berklin has a problem selling them, that why the price drop. All other ones more expensive.Bert Kehren

In a message dated 7/9/2019 11:05:39 AM Eastern Standard Time, lajeunesse at mail.com writes:

Bert,

My take on the issue is that Mark Sims had not seen manufacturer documentation on how specifically to use the sawtooth correction value. You posted a picture of what we now know was an implementation of a use of the correction value. Did you have manufacturer documentation on how the value was to be used before you did your design? If so, that's what Mark is looking for. Like me, Dana was confused by your picture of a GPS assembly, which was not an answer to Mark. Knowing Dana personally I'm not surprised he started down the 20 question path, and I doubt he was actually offended by your post. 

respectfully,
Robert LaJeunesse

> Sent: Tuesday, July 09, 2019 at 6:26 AM
> From: "ew via time-nuts" <time-nuts at lists.febo.com>
> To: time-nuts at lists.febo.com
> Cc: ew <ewkehren at aol.com>
> Subject: Re: [time-nuts] Advantages of GNSS ???
>
> Dana
> This was in response to Mark Sins " I don't think that I have ever seen what to do  with the sawtooth value
>  documented in any receiver documentation"I did this 4 years ago it, is a sawtooth corrected ublox.  First pass. Always do a follow on board but never did any thing with it since there was no interest. We did it part of our GPSDO work but saw no improvement. Sorry my work offends you.I did the same with the Furuno GT and GN-87 without sawtooth since it is only 4 nsec. Ole tested it and we use it with very good results. Again I followed it up with a later design in case there is interest. I will not post the picture of the original one so not to offend you.I will not do a board on the ublox 9 since we are frequency not time nuts and see no need for it. 
> Bert Kehren
> 
> 
> In a message dated 7/9/2019 12:05:14 AM Eastern Standard Time, k8yumdoober at gmail.com writes:
> 
> One what?  I see that it is a Ublox unit, but see no reference to the
> interesting
> modern units like the 9 series.  Also, I note that the only reference on
> the board
> to "ant" is on the lower right corner, while what I suppose to be the
> actual antenna
> connector appears to be an SMA near the upper right corner.
> 
> And why does it look like several of the components have been resoldered
> or replaced or something?
> 
> Dana
> 
> 
> On Mon, Jul 8, 2019 at 8:00 PM ew via time-nuts <time-nuts at lists.febo.com>
> wrote:
> 
> > Well now you can see one
> > Bert Kehren
> >
> >
> > In a message dated 7/8/2019 7:02:07 PM Eastern Standard Time,
> > holrum at hotmail.com writes:
> >
> > A big issue with using the sawtooth correction message from a GPS
> > receivers is the issue of just what that sawtooth value is related to and
> > how to apply it to the measured PPS value / phase.
> > I added the ability to Lady Heather to calculate a sawtooth corrected
> > "paper clock" by applying the sawtooth correction message value to the PPS
> > output measured by an external counter like the TAPR TICC.
> >
> > There are around a dozen different combinations of sawtooth value and PPS
> > measurements...  only one of which minimizes the PPS error.  Do you add or
> > subtract the sawtooth value to the PPS measurement?  Do you apply the
> > sawtooth value to the previous/current/next PPS measurement?  Do you apply
> > the sawtooth correction to the PPS itself or the accumulated phase of the
> > PPS?
> > I don't think that I have ever seen what to do  with the sawtooth value
> > documented in any receiver documentation...  Heather has default receiver
> > dependent correction strategies or lets you specify the correction
> > strategy to use._______________________________________________time-nuts
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