[time-nuts] Re: Power and heat re: Heathkit WWV clock / where are the good oscillators?

[Brooke Clarke]

Hi Joe:

The DS3231 is specified at 2ppm/year out of the box.  But it can be tweaked to much better performance.
https://www.maximintegrated.com/en/products/analog/real-time-clocks/DS3231.html
For example if a clock with a much better stability used the DS3231 as a backup, then it could be tweaked while the main 
clock was running.
https://prc68.com/I/PRC68COM.shtml#07092006

-- 
Have Fun,

Brooke Clarke
https://www.PRC68.com
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------
> Hi all – I've been reading up on the *Heathkit GC-1000 Most Accurate Clock*
> from the 1980s, which syncs with WWV. I've seen numerous reports of the
> flawed power supply and regulator, and the intense heat it generates in the
> chassis, and I'm stumped. Why does it need so much power that it's getting
> hot? There's hardly any computation involved in syncing with WWV, decoding
> its BCD bitstream, etc. Can I expect similar issues if I build my own clock
> instead of restoring a GC-1000?
>
> Quartz watches can sync with WWVB and run for a couple of years on, what,
> ≈200 mAh coin cells? I'm amazed that some are able do GPS, which is far
> more computationally taxing, but I think most of those are solar with a few
> months of battery backup. I don't understand why a WWV clock isn't sipping
> milliamps in cool silence like a watch. Is it something to do with the WWV
> medium band frequencies (5-15 MHz) compared to WWVB's long wave (60 KHz)?
> (Why did Heathkit sync to WWV and not WWVB? I thought the latter has less
> propagation delay.)
>
> The oscillator runs faster than a standard 2^15 Hz movement, but so do lots
> of high accuracy quartz watches. I've looked for an Omega quartz ship's
> chronometer from the early 80s, but they're too rare apparently. It has a
> 2^22 Hz oscillator and runs for a couple of years on two AA batteries.
> (Scroll down to the ship's version:
> https://en.wikipedia.org/wiki/Omega_Marine_Chronometer) And the new Citizen
> Caliber 0100 movement runs at 2^23 Hz, in a watch... (
> https://www.hodinkee.com/articles/citizen-eco-drive-caliber-0100-review)
>
> By the way, why am I not finding any RTCs better than 20 or 15 seconds per
> month accuracy? I've looked on Mouser and Digikey. It's like there's been
> no progress since the 80s. That Omega was good for maybe 0.4 sec/month
> drift, worst case, and the new Citizen is unbelievable at under 0.1
> sec/month. What performance can we expect in a disciplined oscillator like
> the GC-1000's? I haven't found any specs on its *endogenous* accuracy after
> some break-in period with enough disciplining. I'd like to have less than
> 0.1 sec/day between syncs – syncing isn't possible at all hours, and GPS
> won't work for my application. So a 3 sec/month clock on its own. The world
> is full of quartz watch movements more accurate than that, without needing
> ovens, many dating to the 1970s, so I'm confused by why movements that sit
> on a desk and never move are so subpar compared to watch movements. Has
> anyone leveraged a watch movement in a desktop chassis? I wonder about the
> interfaces, since they're all used in analog watches and I don't know if
> they express/output time in a way that can be used by a controller.
>
> Thanks,
>
> Joe
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com