From: bill.sloman@ieee.org   
      
   On 8/01/2026 2:41 am, TTman wrote:   
   > Bac in the early 80s, I nade a lot of money selling 'better than normal   
   > accuracy' digital watches. A colleague designed and made an accuracy   
   > tester that showed +/- 20 seconds/month. The source accuracy was from   
   > MSF Rugby RF transmitter ( 1 pulse/second?). The detector ( I think) was   
   > some form of piezo... it was about 2mm diameter glued into a BNC housing   
   > ( for simplicity). It worked by touching the piezo probe onto the back   
   > of the watch ( with the back off) and I was able to adjust the trim cap   
   > to get close to a few seconds per month ( ignore ambient/body temp)   
   > This probe went into the box via a cable, was amplified and somehow   
   > comaped to the source and converted into secs/month.   
   > Can anyone figure out how this probe was constructed?   
   > Reason- I want to build another one with a 10Mhz reference Xtal etc.   
   > any suggestions welcomed.   
      
   Don't bother. 10MHz reference crystal aren't all that accurate. Get a   
   rubidium stabilised source if you can't pull a proper reference out of   
   the ether. Global positioning system reference frequencies are lot more   
   accurate than any 10MHz reference crystal, and there are other broadcast   
   frequencies which are almost as good.   
      
   The standard watch crystal is a 32,768kHz piezo fork, and if you put one   
   close to the metalwork around an active crystal in watch it would   
   presumably get mechanically excited by the watch crystal, and you should   
   be able detect an electrical signal on it's leads that would track   
   frequency being generated inside the watch.   
      
   The sensing crystal is unlikely to be resonant at exactly the same   
   frequency inside the watch so there would be a little phase lead or lag   
   between them, but it would be stable.   
      
   I've never seen it done, but it ought to work.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)