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Clock
On 02/12/2018 5:36 PM, Paul wrote:
Rene Lamontagne wrote: On 02/12/2018 1:25 PM, Paul wrote: Mark Lloyd wrote: On 02/11/2018 01:08 PM, Peter Percival wrote: Ken Blake wrote: If you want to know the time very accurately, of course a digital clock is more better. How come?* There is nothing about digit clocks that mean that they can't be wrong. Sorry, I used the wrong work there. It should be "precision". However, some clocks are now controlled by internet or radio, and are more accurate. The radio are really the best, because you never have to adjust them. All they need is a source of power, and they don't need a 60Hz reference to keep time. The radio that does that, is at low frequency, like 60KHz. The frequency used, varies with country or locale. (And this is not GPS either. This works even if GPS was knocked out. The reason for not using GPS, is the GPS constellation might not be receive-able inside your house. 60KHz penetrates buildings a lot better.) You may not get a usable signal during the entire 24 hour day, but in good circumstances, your "radio clock" is synced at least once a day. Even if your clock has a 100ppm xtal, it doesn't matter, because the radio sync will bring it back to where it should be. You don't have to have an atomic clock in the box. The antennas used, come two ways. You can use a wire loop with huge dimensions (i.e. you'd better be on a farm). However, using ferrite rods, you can make a compact design that is just as good. The one pictured here, might have been removed from the back of a commercial wall clock. That's to give an idea of how big a non-hobbyist one is. https://electronics.stackexchange.co...-wwvb-receiver The Russians make the best ferrite rods for this. Ferrites are available in a number of compositions, and I don't think there's much commercial interest in making the rods for this application. But I've seen hobbyists who claim some Russian-sourced rods worked well. I've seen some designs, that have multiple ferrite rods with the wire wrapped around the whole bundle. This is one of those niche hobbyist activities (if you want to build your own, rather than buy one). I think most people who dabble in this, they want the sync info to be available all day, and that's why they want their design to be more sensitive than a store-bought one. If the central transmitter goes down, then no more sync for you. You're on your own then. An EMP could easily knock out such a site. Or government cutbacks. You can also buy the pre-built ones if you want. But you'll need something to decode the serial output and actually use it. You know, the rest of your "clock" :-) https://www.ebay.com/p/3-Pcs-WWVB-60...38#UserReviews *** Paul My La Crosse weather forecast station has a built in one tuned to WWVB, If I want to set all the other clocks in the house this is the reference I use. Rene Does it have a LED that indicates when the 60KHz carrier is present ? There is a coverage map for the USA, and the signal strength contours change with time of day. ** Paul No, it has a Little icon of a satellite dish with waves emanating from it. If the carrier is not locked in the icon disappears Rene |
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