[time-nuts] Sidereal timekeeping

[Hal Murray]

> does anybody out there have any ideas as where to find a 32859Hz crystal (1/
> 2  that value would be better) to be used to replace 32768 crystals in
> ordinary  clocks? I think that 32768 crystals cannot be dragged that much.
> I've already  read the JimLux article somewhere on the web, but I would be
> pleased finding a  simpler solution. Also, I already have computer programs
> that show sidereal  time. 

I think it depends upon what you mean by "ordinary clocks".

Most of the recent wall clocks I've seen are battery powered (single AA) and 
resynchronize nightly via WWVB.

If you want sidereal time, you won't have anything to synchronize to.  What 
sort of accuracy are you interested in?  If you want reasonable accuracy, you 
will need an external signal.  (You can provide power over the same cable.)

My straw man would be to send 32859Hz down coax or twisted pair and feed it 
into the xtal-in pin on the clock chip.  I'm not sure how to set the time.  
You can cut the lead to the antenna to make sure it doesn't sync to WWVB.

You can make 32859Hz from a PIC (or any micro you like) running off any handy 
frequency.  Given that this is time-nuts, I'd suggest 10 MHz from a GPSDO.

It might be simpler to dump the 32KHz and WWVB chip and drive the motor 
directly from a 1 PPS signal.  Just use a sidereal second rather than a 
normal second.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.