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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.
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You'd think they'd be a bit more accurate than just "On July 5th"
rewriting history since 2109
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.
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Ah, no, it's the muppets at Telstra who clearly don't come from Queensland, Western Australia, or the Northern Territory.
Patent litigation: A doctrine of Mutually Assured Destruction... in which everyone seems willing to push the button
So anyone here tried using a software defined radio setup to receive and decode the WWVB signal?
Is it too much to expect the quotation in the summary to actually come from the linked article? In part it says "Recent upgrades, ... will allow the station to be better received even in large buildings." My curiosity was piqued. What were these upgrades? Not only was there no explanation in the Wired article, none of the text quoted in the summary seems to appear in the article. WTF?
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I wonder how is it measured. Anyone knows?
" $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...
An accuracy of 1 part in 70 trillion. Yeah. Maybe right at the clock they use. But people setting their clocks by it live a distance from the station. And the speed of the radio waves is finite. So the further from the station the less effectively accurate the signal is (people don't measure the exact distance they are from the source so they can't know the real time when they get the signal). The time to receive could be a second or two behind the real time for someone receiving on the far side of the earth. So how does touting their supreme accuracy reflect on actuality? Not well. I wonder if it is worth creating a super duper accurate time keeping service that can't be received accurately.
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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
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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.
Nist revised the WWVB format, it now carries two time signals on the same carrier. The enhanced time signal encodes the date/time as a 26 bit number with 5 parity bits. Absolutely foolproof, no, but there is now error checking for clocks that support this new format.
Back in the early 1980's, my group used the Heathkit radios to synchronize portable seismographs. "At the tone, the time will be..."