Even though it seems like I’m always running late, I’m anal about keeping my watch accurate to the second. Thus, I’m a big fan of NTP and radio-controlled clocks. In fact, I’m considering getting one of those “atomic” Casio watches.
Last month NIST updated WWVB Radio Controlled Clocks: Recommended Practices for Manufacturers and Consumers (PDF), its guide to making and using WWVB-controlled clocks. WWVB operates at 60kHz, way down in the low frequency band. A half-wavelength antenna for WWVB would be a little over a mile and a half long. NIST also operates WWV, which broadcasts at 2.5, 5, 10, 20, and 25MHz.
Building a WWVB-controlled clock is on my list of electronics projects, but it’s not one I intend to get to anytime real soon.