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

[Bob kb8tq]

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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