Reducing the mains voltage to save energy

[JohnD]

Fair enough - but, as I said, during those inbetween-synchs periods they could, if mains-powered, synch to to the mains (rather than a local oscillator) if they so wished. Mind you, crystal oscillators are so stable over the sort or time period we're talking about that I can't see that there would be much point.

Kind Regards, John

I heard from someone in the watch trade that quartz watches can be made incredibly accurate, and if you buy a cheap one, it is deliberately manufactured to be inaccurate, so that there will be an advantage in buying an expensive one.

 

[Harry Bloomfield]

I heard from someone in the watch trade that quartz watches can be made incredibly accurate, and if you buy a cheap one, it is deliberately manufactured to be inaccurate, so that there will be an advantage in buying an expensive one.

They can specially select the crystals and components around it, to be extra temperature stable and take extra care with the calibration to get better accuracy, but even cheap quartz watches are incredibly accurate compared to their expensive mechanical counterparts.

If more accuracy is needed from a crystal oscillator, the usual way is to have it installed inside a temperature stable oven. I have two such in frequency counters which cost several thousands of pounds and a fancy frequency standard with an ovened reference. You switch them on, then wait an hour for them to settle before they attain full accuracy.

 

[SimonH2]

That read a bit confused..

Yes, I suppose it was, sorry about that.

NTP is not a radio time source it is an Internet time source, several servers in fact. MS Windows uses NTP sources to sync the PC's clock maybe once per week, if Internet access is available. Being a bit obsessive about having the right time, I have edited my Registry so my computers resync every hour.

NPL / MSF is on 60Khz and transmits (apart from outages) continuous time codes, in the form of a full data set over one minute, and optionally a fast code croak. I wrote what was probably the first computer code to receive and decode it back in the 1970's.

NTP is a protocol - mostly used with internet located time sources, "NTP servers". You can run NTP (or more accurately, a daemon process), but use other time sources - such as GPS or MSF receivers. There are commercial units which incorporate a GPS of MSF receiver, maintain an accurate internal clock, and re-distribute that via the NTP protocol - or you can buy just the receiver and plug it into your own system with the right driver.
That Windows "syncs the clock" periodically suggests that the Windows time management isn't very good - I am not familiar with the internals of Windows time management. Typically the NTP daemon on Unix like systems runs continuously - it does not sync the clock (except at startup), it carefully tweaks it so that it comes into sync with the source it's chosen as the master.