RevDisk informed us:
The actual atomic clock is situated in the NIST building off Broadway in Boulder, Co. The time signals generated thereby were transmitted through a subchannel of one of the Denver TV stations up to the time transmitters located in Fort Collins CO.
OK, so the Boulder Amateur Radio Club (BARC) used to have its meetings in their auditorium and they used to have a large digital display of the atomic clock time over the main entrance, just past the guard station.
Every time I went in there for a meeting, I'd make a big show of looking back and forth from my watch to the display until I caught the guards' attention, and then point to the display and tell them, "It's slow."
Yeah, I know, I'm an
Ok, that is funny. I hope the guards laughed.
I thought that the US had two official master clocks, just in case. Apparently that wasn't the case but now is again. NIST-F1 was the solo official US master clock. But now NIST-F2 is operational and planned to be accurate to 1 second every 300 million years. The backup is the U.S. Naval Observatory master clock in DC, and the USNO Alternate Master Clock in Colorado.
I'm kicking myself for not going for a tour last time I was in Boulder. How was it?
Question about the atomic clock... specifically the time signal.
How do they adjust for the time lag between a clock 10 miles away receiving the signal vs a clock in, say, Eastport, Maine, about 2,300 air miles away?
Even though the signal travels at 186,000 miles per second, there's still a measurable lag.
And, if it's used to establish time for the GPS satellite network, that's even more of a signal lag
For radio, you do indeed get lag. You calculate it by your distance from the transmitter. It's a fixed variable, as the US is only growing by 1cm per year. Give or take. It's a rough estimate, but generally within tens of milliseconds. Which isn't bad. NTP is similar accuracy. If it's important enough to matter, they've already factored it in.
With GPS, the lag is the source of the accuracy and why you need multiple satellites. You compare the transmissions from the different sources and you get a location. Nifty thing is, the entire system is dependent on super accurate timing. Tens of nanosecond range, rather than millisecond. The amount of lag isn't important, it's how precisely you can measure the lag that defines the accuracy. In another five years, we'll have GNSS receivers that can use GPS, GLONASS, Galileo and BeiDou-2.
Nifty bit of trivia, GPS compensates for Relativistic speed impact on time.