I’m thinking of getting one. Do they work? Any problems or pitfalls I should know about beforing buying it?
I meant to say “before.” :smack:
They work very well, as long as you can get a signal. In fact, we use them where I work as a reference standard for calibrating long-term timers (stop watches, etc.) I even wrote a ISO-approved procedure for it.
One thing you want to keep in mind is that most atomic clocks are not continuously “locked in” to WWVB, even if the clock is in a location where it can pick up the signal. Most of the time an atomic clock is “freewheeling” using its onboard crystal oscillator. Every so often (typically 2 to 6 times per day) the clock re-synchronizes to WWVB. This means that, in order to achieve millisecond uncertainty, the onboard oscillator must be very stable and accurate.
I don’t think anybody’s really going to sell you an atomic clock. Those things are darn expensive, but indeed darn accurate.
You could, however, buy a watch that’s regularly set to the correct time via radio from a station controlled by an atomic clock (in the US, the [urlhttp://www.boulder.nist.gov/timefreq/]National Institute of Standards and Technology provides this free service). Those clocks actually are more accurate than non-radio ones, although nowaday’s cheapo quartz clocks surely provide suffiecient accuracy. One of the main benefits probably is that you don’t have to change them to Daylight Savings Time and back.
As mentioned signal is the issue. It’s a relatively weak signal in my area (Eastern Shore of MD) so if you’re inside a brick and mortar building your chances of hitting a signal consistently are 50/50 in my experience. Having said that atomic clocks are getting so cheap now they’re typically only a few bucks more than the non-atomics, so you have little to lose.
I bought a $20 atomic-linked watch and it served me well for many weeks. Then I somehow smashed it just a bit and water seeped in and you can figure the rest.
It would check once a day at 3am.
They’re damned pieces of junk. I was late for a meeting because of one.
How do you explain to your boss why you were .003 seconds late for a meeting?
I was recently at a school in Dowagiac, Michigan near the Indiana border. The “atomic” clocks in the building were all set to “Northern Indiana” time, which is Eastern Standard Time, instead of Eastern Daylight time. Do you have to set a time zone on these clocks?
Our clock has a switch for time zone and for switching to daylight time in the summer. Ours also has a hard time getting a signal in our brick townhouse.
The signal strength for WWV (Colorado) and VB (Hawaii) vary by location, time of day, season, frequency (2.5, 5, 10, 15, and 20 Megahertz - don’t know what frequency the clocks are locked on) and sunspot activity (and who knows what else). If you have problems with signal strength, you can try a long wire (one end thrown up in a tree) wrapped around the clock (or wrapped a couple dozen times around a hollow form - plastic tube placed next to the clock). This will inductively couple the wire to the clock and increase signal strength. Experiment with wire length, height, and orientation, and I’m sure you’ll find adequate signal. 
Given the weakness of the signal, anyone know why they don’t have a repeater on the East Coast?