[time-nuts] Mentorship needed in learning about Allan Deviation and variation.

[Joe & Gisela Noci]

Bob, Thanks for that. I am going to dig!

Joe

On Tue, Nov 10, 2020 at 7:56 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> If you are handling the sawtooth correctly, you should see no hanging
> bridges
> at all. My guess is that the spikes are coming from a problem in the
> sawtooth
> correction “stuff”. With no correction, you *will* see a spike as is rolls
> over. With
> a correction error, you would also see a spike.
>
> Bob
>
> > On Nov 10, 2020, at 11:37 AM, Joe & Gisela Noci <jgnoci at gmail.com>
> wrote:
> >
> > Hi Bob,
> > Yes, I am - I use a Dallus digital delay line in series with the GPS 1pps
> > and program the delay line each second with the GPS delay estimate in the
> > GPS NAV message.
> > It works really well, jitter on the 1pps pulse is hugely reduced, but one
> > side effect is that those 'hanging bridges' can become severely extended
> in
> > time.
> > I can by pushbutton selection bypass the delay line, ie, no sawtooth
> > correction - since I do not have a reference frequency source, I cannot
> say
> > if it is better or worse.
> > However, the logged values output from the time-digital convertor still
> > shows the spikes either way- I still suspect the spikes are conversion
> > artifacts from digital noise in the box..
> > Being green on the science of this I packed to much 'stuff' into the
> > enclosure and there are DC-DC converters for power, Nucleo processor
> > running at 140MHz, a NEXTION touch screen LCD, which
> > I am discovering is very noisy, etc....It is difficult to target any
> > solution at the moment as I believe there are too many areas that are
> > marginal - I need to clean it up!
> > Joe
> >
> > On Tue, Nov 10, 2020 at 6:24 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> >> Hi
> >>
> >> Are you using sawtooth correction?
> >>
> >> Bob
> >>
> >>> On Nov 10, 2020, at 8:55 AM, Joe & Gisela Noci <jgnoci at gmail.com>
> wrote:
> >>>
> >>> Hi everyone,
> >>> Still playing with my GPSDO..The Rubidium source I was hoping to have
> the
> >>> loan off did not work out, so still in the dark. I have sort of
> convinced
> >>> myself to procure a reasonable 'proven' source, Rubidium or whatever,
> but
> >>> that
> >>> seems to be more easily decided than done..Or at least so if the money
> >>> available is not astronomical... Also complicated by the difficulties
> >>> getting the goods here to Namibia!
> >>>
> >>> Anyway, I am still unhappy with my analogue time-to-digital conversion
> -
> >> I
> >>> do see the odd spike in the logged data and have been unable to find
> why
> >> -
> >>> have applied lots of filtering of supplies, used a separate A/D
> >> convertor (
> >>> as opposed to the convertor internal to the STM Processor) with own dc
> >>> regulated supply, own clean A/D Reference voltage ( 1ppm device).
> etc...
> >>>
> >>> Does not mean implementing a digital method will get rid of the spikes,
> >> so
> >>> I am still chasing that till I understand, but to that end:
> >>> I found this device and am keen to get the dev kit and try it out :
> >>>
> >>
> https://www.sciosense.com/products/time-to-digital-converters/development-kit-for-as6500/
> >>>
> >>> Has anyone perhaps played with it? Would be interested to know more
> about
> >>> it if so..
> >>> Regards
> >>> Joe
> >>> V51JN / ZS6JGN
> >>>
> >>> On Wed, Oct 28, 2020 at 7:08 PM Alberto di Bene <dibene at usa.net>
> wrote:
> >>>
> >>>> On 2020-10-28 2:29, jimlux wrote:
> >>>>> I'm still agitating for alien deviation - Microsoft offers it as a
> >>>>> suggestion, but not Allan, so it must be true.
> >>>>
> >>>> :-):-):-)
> >>>>
> >>>> Thanks Tom and Jim for the explanations. All clear now.
> >>>>
> >>>> 73  Alberto  I2PHD
> >>>>
> >>>>
> >>>>
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> >>
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