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Comment by caf | Hacker News Reader

It'd be a fun project to make a dial wall clock that uses GPS time.

GPS would be tricky to receive in a typical hotel or office lobby (i.e. far away from any windows at the ground floor, possibly in an urban canyon).

In Germany (and in neighboring countries), radio-controlled clocks are quite common for this purpose, listening to DCF77 near Frankfurt [1].

Long wave seems to work a bit better than the L-band for indoor propagation, and it probably also helps that the transmit power is three orders of magnitude higher.

I'm not sure if the US has an analogous service – there's WWV and WWVH, but they are shortwave transmitters, and I don't know if wall clock or even wristwatch size receivers are possible for that.

[1] https://en.wikipedia.org/wiki/DCF77

> I'm not sure if the US has an analogous service – there's WWV and WWVH, but they are shortwave transmitters, and I don't know if wall clock or even wristwatch size receivers are possible for that.

It does. Small WWVB clocks that self set are quite common.

Yes, works for small clocks and watches, but they have mostly moved to gps these days, at least for auto sync watches.

WWVB is running at 60kHz, and powers at least a few of the small desk clocks in my home :)

https://en.m.wikipedia.org/wiki/WWVB

I think you can still buy NTP reference devices for your network that use GPS. So, the lobby of the hotel doesn't have to be within view of the sky, as long as their reference device is.

Meinberg is just one of several companies I've seen that sell clocks that are NTP clients.

It makes sense that a company might make those, if they also make the NTP servers that those clients might be connected to.

Good stuff. I'm planning on buying some for the house.

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