
A Brief History of NTP Time: Confessions of an Internet Timekeeper (2003) [pdf] - lelf
http://www.eecis.udel.edu/~mills/database/papers/history.pdf
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PeterWhittaker
I've long been impressed by how many key contributors to the IETF were not
only among the top practitioners in their fields but also fantastic writers,
able to describe their work and necessary next steps with just the right
balance of simplicity and complexity and always with clarity.

Many of the more important RFCs are almost a joy to read, and this article -
written by the author of many of the NTP-related RFCs and predecessor docs -
is a gem: Clear, concise, to the point, balanced, informative.

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rwg
Section 4 ("Radios, we have Radios") really dates this article.

 _DARPA purchased four of the Spectracom WWVB receivers_ [...] _The radios
were redeployed in 1986 in the NSF Phase I backbone network, which used
Fuzzball routers [26]. It is a tribute to the manufacturer that all four
radios are serviceable today_

Those receivers almost certainly aren't in use anymore.

There's a real problem with WWVB reception here on the east coast of the
United States, especially in urban areas. NIST investigated several
possibilities for improving reception, including building a second WWVB-like
transmitter site in Alabama. (That plan ended up dying because of a dispute
with NASA that never got resolved before the funding expired.) So they went
with Plan B, a public-private partnership with a company named Xtendwave,
where Xtendwave worked with NIST to design a phase modulated signal format for
WWVB, NIST implemented the new phase modulated signal, and Xtendwave filed for
and received patents on it all.

So NIST is currently broadcasting two signals on WWVB's carrier: the old
amplitude modulated signal, which is prone to interference, and a new phase
modulated signal that's more resistant to interference and has error-
correction built-in. Unfortunately, when the phase modulated signal appeared,
all of the "laboratory grade" carrier tracking WWVB receivers in the world
(like Dave Mills' Spectracom receivers and a Kinemetrics/TrueTime receiver I
had at ${PREVIOUS_JOB}) became instantly obsolete — they can't lock onto a
carrier that's constantly, unexpectedly going 180° out of phase.

It's worth noting that Xtendwave has been saying that their line of receiver
chips for the new phase modulated WWVB signal will be available Real Soon Now™
since at least late 2012, but you still can't buy them. Also, no one seems to
know if you can build your own receiver for WWVB's phase modulated signal
without running afoul of Xtendwave's patents.

So, yeah, NIST obsoleted working equipment actively used in industry in order
to provide a "better" time signal that nobody can actually make use of. Yay.

 _These four radios, together with a Heath WWV receiver at COMSAT Laboratories
and a pair of TrueTime GOES satellite receivers at Ford Motor Headquarters and
later at Digital Western Research Laboratories_

GOES is NOAA's geostationary weather satellite program, and NOAA used to
broadcast a publicly documented timecode from those satellites. NOAA finally
killed the time service a decade ago because GPS existed, there was almost no
funding to keep the GOES timecode going, and the ground hardware used to drive
the service was obsolete.

There's a nice GOES retrospective at
[http://tf.nist.gov/general/pdf/2013.pdf](http://tf.nist.gov/general/pdf/2013.pdf)

