> WWV is the oldest continuously operating radio station in the United States. It's been on the air since 1920. It's signal provides a frequency standard for receivers. The time stamp is regulated by an atomic clock. But a 2019 budget proposal for NIST would close WWV, WWVH in Hawaii and WWVB, which syncs up the time for about 50 million radio-controlled clocks, wristwatches and appliances.
Classic example of the government providing a pure utility, a utility with no profit motive, which private enterprise could never justify.
Not to mention it's impossible to even charge for this service. I guess you could encrypt the stream, but a single key leak compromises everything (unless you assume devices are connected to the internet, which defeats the purpose of the system).
Satellite TV providers manage to make it work: each receiver has its own key in a smartcard, and the master key which encrypts the broadcast is gradually distributed to each receiver over the same radio channel. The master key is changed often, so leaking it once is not enough.
We do. GPS is actually more accurate. That said...
1. GPS requires a clear line of sight to the sky. Doesn't work for indoor clocks.
2. Shortwave receivers are more energy efficient.
3. Redundancy is a good thing. Just in case GPS (or your receiver) has a problem.
4. WWV isn't just time. It also serves as a frequency reference for radio stations. It also transmits marine weather alerts, space weather (solar flares, etc.), and GPS system health updates. (Though apparently the marine weather notices are being discontinued in Jan 2019.)
I have a wall clock that syncs from WWVB. It was pretty cheap and uses a single AA battery (which seems to last forever). I never have to update the time.
Can satellite time provide an equivalent or better solution here?
To get halfway decent holdover performance, you want all the precision you can get when the constellation is good. That requires the best skyview (and least multipath) you can manage.
You can see only about half the sky that way, which means usually getting almost as good a fix as with a roof mount antenna. For best results, you want the satellites to be as far apart as possible in the sky (measured by angle from your position, not miles between them). See https://en.wikipedia.org/wiki/Dilution_of_precision_(navigat... .
If you mainly care about time and can tolerate a few microseconds of error, usually being able to see 4 satellites might well be enough.
I remember seeing a gps receiver designed just for time that could maintain sync using only one satellite (it assumed that it was bolted to an immovable object, and it might have needed to see 4 satellites at once at some point).
Classic example of the government providing a pure utility, a utility with no profit motive, which private enterprise could never justify.