[jaggederest]

In the 80s my uncle had digital clocks that used an antenna to tune into the atomic clock time signal that (was/is?) broadcast nationwide. I've long wished that it was incorporated into stoves, microwaves, essentially everything that isn't an internet device (yet... sigh)

Sadly I think the actual antenna and hardware were relatively large since it's a long wave signal, but maybe with SDR it'll all fit on the head of a pin these days.

[raron]

> atomic clock time signal that (was/is?) broadcast nationwide

Probably DCF77 or WWVB.

> I think the actual antenna and hardware were relatively large since it's a long wave signal

Casio has some normal sized wristwatches that synchronizes to DCF77, it would definitely fit into a stove, microwave, or basically anything.

[jaggederest]

I believe it was a longwave broadcast so probably WWVB which would apparently imply a 60mm antenna, but it was a standard old school "GE digital clock radio" form factor so size wasn't at a premium.

[jasonwatkinspdx]

> Sadly I think the actual antenna and hardware were relatively large since it's a long wave signal, but maybe with SDR it'll all fit on the head of a pin these days.

Unfortunately there's no real way to cheat physics as far as shrinking a wavelength goes. With RF antennas about the best you can do is a major dimension 1/10th the frequency of interest.

[namibj]

There are many DCF77 receivers in Germany that are contained in a square box that's barely large enough for a AA battery; the rest of the square contains the motor/gears and the electronics/receiver (incl. a ferrite loopstick antenna).

The wavelength is around 3.8km...

[jasonwatkinspdx]

Yeah, that's because it's receiving an extremely narrowband signal accumulated over a long window so it can suffer the trash efficiency I'm talking about.