[time-nuts] Re: Crystal oscillator for a begginer

[Keelan Lightfoot]

For the curious, the source for this is here: 

https://web.tapr.org/~n8ur/PIC_Code/

When I read that it uses a only a PIC, I was skeptical, but then when I read that jitter is in the range of 1 pico second, I was intrigued. It’s a neat solution, the 10 MHz input signal is used as the clock for the PIC, the code relies on a hand crafted carefully timed loop and the PIC’s fixed 400ns instruction cycle to create a very stable output. Crafty. It’s a bit like the Atari 2600 running in lock step with the horizontal blanking period. 

Ahh, I see Tom Van Baak is responsible for this idea. Nice work!

> On Jan 5, 2022, at 5:59 PM, W7SLS <w7sls.scott at gmail.com> wrote:
> 
> Adam,
> 
> You might already know this, but if not …
> 
> To add on to Bob’s suggestions, if you have more money than time,
> TAPR has some ‘divide to 1 pps’ devices:
> 
>    https://tapr.org/product/tadd-2-mini-pulse-per-second-divider/
> 
> And some ‘compare 1 pps devices’:
>    
>    https://tapr.org/product/tapr-ticc/
> 
> I have no financial connection to TAPR, except as a member (hmm, time to renew, probably).
> 
> Good luck on your adventures!
> 
> Sent from my iPad
> 
>> On Jan 5, 2022, at 5:33 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>> Hi
>> 
>> In general, eBay is your friend for stable crystal oscillators at a 
>> “friendly” price. Even if you buy 10 to get one, the price is still pretty
>> good. What you learn testing them is indeed “Time Nut Stuff”. 
>> 
>> Just what’s a good deal varies almost week to week. It is very much a 
>> shop shop shop sort of thing. 
>> 
>> Best / quickest / easiest way to use all these gizmos: Program up a PIC 
>> to divide them to 1 pps and go from there. 
>> 
>> Bob
>> 
>>>> On Jan 5, 2022, at 6:01 PM, Adam Space <time.isanapp at gmail.com> wrote:
>>> 
>>> My question is rather open ended. I'm relatively new to timing and whatnot.
>>> So far I have mainly dabbled in NTP, and some GPS stuff with a Raspberry Pi
>>> with a GPS hat. But both of these are limited to timekeeping on an actual
>>> computer system, but I'd like to get into some of the more hardware stuff,
>>> and I figured a crystal oscillator would be a good place to start.
>>> 
>>> My knowledge of hardware is pretty weak, so I am unsure of how stuff works
>>> in this realm. For example, a quick google search shows very cheap crystal
>>> oscillators, like these
>>> <https://www.digikey.com/en/products/detail/cts-frequency-controls/MXO45-3C-10M000000/1801887>.
>>> But I am confused on how I could exactly use this. One thing I like about
>>> NTP is that I can see and compare different clocks, and synchronize them
>>> to time-scales like UTC, and track their performance over time. But if I
>>> have a crystal oscillator going, how could I compare it or adjust it to
>>> other clocks on my network, or to UTC for example?
>>> 
>>> Or to take another example, suppose I have a few crystal oscillators like
>>> the one above. Is there a way I could compare them to each other, or log
>>> the offsets from each other, and so on? Ultimately, it would be nice to
>>> compare the frequency and time offsets to a reference source that is
>>> accurate long-term, like my GPS hat Raspberry Pi.
>>> 
>>> Any ideas, suggestions, or clarifications are welcome. Additionally, if
>>> anyone knows of any guides (either text, video, or whatever), that would be
>>> great too.
>>> 
>>> Adam
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