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WWV Shortwave Time Broadcasts May Be Slashed In 2019 (qrz.com)
New submitter SteveSgt writes: A forum thread on QRZ.com indicates that the shortwave time broadcasts by the National Institute of Standards and Technology (NIST) from stations WWV (Colorado) and WWVH (Hawaii) may be slashed in budget year 2019. [One of the proposed reductions includes "$6.3 million supporting fundamental measurement dissemination, including the shutdown of NIST radio stations in Colorado and Hawaii."] While the WWV broadcasts may seem like an anachronism to some Slashdotters, they remain a crucial component in many unexpected services, from over-the-air broadcasters and traffic signals, to medical devices, wall clocks, and wrist watches. The signals serve as standard beacons for radio propagation, and as a frequency reference for alignment of a broad range of communications equipment. It's easy to imagine that not even the NIST knows every service and device that could be impacted by this decision.
on 60 kHz. The WWV/WWVH services being cut are on HF (2.5-25 MHz).
The loss of those frequencies will obsolete the older HF clocks, like the Heathkit GC-1000 "Most Accurate Clock" I have in my ham shack. As well as removing the other functions they provided besides time, such as precision frequency reference (zero beat a signal generator or receiver VFO against WWV's carrier, and you know it is exactly on frequency), and the various frequencies throughout the HF band provide useful propagation checks, as well.
Oh well, the $6M they save can pay off a lot of porn stars, or cover the security detail for a couple rounds of golf in Bedminster...
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I don't have any good links, but it's not too complicated...
The radio beacon travels at (roughly) the speed of light. That's about 300 million meters per second, so there's a 1ms delay after the signal gets to be 300 km away.
From a technical perspective, all communications (including Internet-based systems) are bound by that same speed, and trying to break that cosmic limit has proven to be extremely difficult, so engineers have done what engineers do best: they cheat.
The "fancy" algorithm is really pretty simple, conceptually: Instead of just accepting a time beacon, the NTP client measures how long it takes to ask for a time, and assumes that the time it receives was accurate halfway through the round-trip time. For example, if it takes 14ms to get a message saying it's exactly noon, that message was probably received very close to 7 ms after noon, so NTPd will set the local clock accordingly. It's not perfect, because the round-trip time might not be symmetrical, but it's close enough for most practical purposes. Using WiFi might add a bit of delay, but as long as the delay is symmetric, it won't be a problem.
The key for NTP is that it's a client-server protocol, so the client knows approximately how long the message was in transit. A one-way radio beacon like WWV doesn't have that, but that also means WWV doesn't need to receive transmissions from clients to function.
GPS is even fancier. A GPS satellite transmits not just a time beacon, but also a message with the satellite's location when the beacon was sent. Once a receiver has learned the locations and delays for at least four satellites, it can start to determine its own location. First, it will compare the satellites' locations and delays relative to other satellites to figure out where the receiver could possibly be on Earth. Then it can use that location to determine the exact delay for each satellite's signal, which is then used (just like in NTP) to compute the actual time.
GPS is superior to both NTP and WWV, because it is still a one-way communication system, but also isn't subject to any network traffic or assumptions about symmetry. With no prior knowledge, a GPS receiver can accurately compute both its location and time.
You do not have a moral or legal right to do absolutely anything you want.
It's also sad how badly misunderstand the US constitution.
The constitution is not law.
The constitution is a framework which all laws must conform. This is a significant difference.