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WWVB Celebrates 50 Years of Broadcasting Time
First time accepted submitter doublebackslash writes "On July 5th, WWVB, NIST's timekeeping radio station transmitting near Fort Collins, will celebrate 50 years of continuous operation. Operating at 60kHz, the signal actually follows the curvature of the Earth via a trick of electromagnetics, allowing nearly the entire globe to receive an accurate time signal, which has in recent years reached an accuracy of 1 part in 70 trillion. Recent upgrades, which came in $15.9 million under budget will allow the station to be better received even in large buildings, giving it an edge on timekeeping that not even GPS can touch, with its need for open skies to receive a signal."
It also operates at 5MHz, 10MHz, 15MHz, and 20MHz.
Only the State obtains its revenue by coercion. - Murray Rothbard
You'd think they'd be a bit more accurate than just "On July 5th"
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Some 15 years ago, when they were at their original low power, my area was so fringe that my fancy new WWVB wristwatch just wouldn't pick it up.
The protocol is really quite straightforward and well documented at their site. The 60kHz signal sends binary by sending either full power or a bit less (I forget how many dB). I used a computer synced with NTP and a plain old soundcard generating 60kHz from a sound card into an audio amp, and I just did either full on or full off. The output ran into a big coil that I had wound to be roughly resonant around 60kHz.
Much to my amazement, it worked. So I just kept the watch near that coil overnight and it synced perfectly, until WWVB cranked up their power at which point I retired the mess.
>"Operating at 60kHz, the signal actually follows the curvature of the Earth via a trick of electromagnetics, allowing nearly the entire globe to receive an accurate time signal"
Except it doesn't. It depends on time of day, weather, season, exact location, how much local interference, building construction, elevation, and many other factors.
I really WISH it were as strong and wonderful as implied in the summary, but it is not. I have used radio controlled, WWVB clocks for many years and one thing they are NOT is "reliable", at least not where I live. Of the dozens of clocks I have used over 20+ years, NONE of them could get a reliable signal anywhere I have lived in the Mid Atlantic coast of the USA.
I am lucky to have it sync several nights in a row and then go weeks without a signal (sometimes even a month). Unfortunately, none of the clocks I have seen will store a step adjustment, so they drift just like any other quartz clock- some are even worse than just a cheap $15 non-radio-controlled clock.
Having to constantly set and sync clocks on everything (except my computer equipment and SOME of the radio clocks) is really annoying in 2013. With all that freed up VHF TV, why couldn't the government have set aside just a tiny blip that could be used for another time sync that could penetrate buildings and work in the daytime and regardless of weather?
Oh well. WHEN it works, it is nice.
WWVB time propagation isn't accurate to 1.4 e-14, as stated. The souce might be, but propagation delays and variability make it so you can get nowhere close to that upon reception. GPS is better in all respects, other than perhaps reception in some particular locations.
"National Security is the chief cause of national insecurity." - Celine's First Law
So anyone here tried using a software defined radio setup to receive and decode the WWVB signal?
NIST changed the broadcast format to include some phase modulation.
"National Security is the chief cause of national insecurity." - Celine's First Law
" $15.9 million under budget"
Sure that'd be be a nice change for some billion dollar government project - to run a little under instead of doubling the budget,
But this was a budget of $16 million...
We had several KWR-37 devices that needed time sync to under one second worldside with the transmitting station when changing daily key cards. WWW()x was great until you where some where past SE asia, then we used the Russia time sync RWM to lock devices,
http://en.wikipedia.org/wiki/RWM
http://en.wikipedia.org/wiki/KW-37
http://www.nsa.gov/public_info/_files/uss_pueblo/Section_V_Cryptographic_Damage_Assessment.pdf
In GOD we trust, all others we monitor.
The time to receive could be a second or two behind the real time for someone receiving on the far side of the earth.
No, it can't. The Earth's circumference is about 25,000 miles, which means that nothing can be more than 12,500 miles away by the shortest route. Considering that the speed of light is roughly 186,000 miles/second, the maximum propagation delay is about 67.2 ms.
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You don't even need that, you can just use an appropriate ferrite rod and decoder board with a handful of discrete components and hook it up to a serial port.
http://www.buzzard.me.uk/jonathan/radioclock.html
It uses what I call the Woz method, aka minimal hardware, do it in software. You will actually get a better result using that method as well because the computer is capturing the timestamps of the signal edges directly without it going through some intermediate process.
One day I will get around to doing the super noise filtering version using Baysian statistics. Basically the more accurately you already know the time the more you can filter the noise out of the signal.
Back in the early 1980's, my group used the Heathkit radios to synchronize portable seismographs. "At the tone, the time will be..."