Any suggestions for gear and/or software that works with WWV (or CHU)?
Or general suggestions for non GPS sources of time?
Hey Hal!
In North America, WWV and CHU are pretty much it for accessible
backups these days. Unfortunately time and frequency distribution is a
niche that tends to get neglected (if not actively gutted) in US
budgets.
Dave Mills had a driver in ntpd that used a PC audio port to listen to WWV.
I don't know anybody who ever used it. I think there was code to tell some
brand of receiver with a serial/USB port how to change frequencies so you
could use the one that worked best for that time of day.
You do now. The WWV and CHU audio drivers work fine. If you
want the auto-tuning functionality, you need to use an Icom receiver
that supports their CI-V protocol. (This can be a full fledged tabletop
like the R-75, or a more compact receiver like their PCR-100 or 1000.
Some of these are no longer produced, but they're easy to come by on the
secondary markets. I picked up multiple PCR-100s off eBay at $25 ea a
while ago.)
You can always use any shortwave receiver, and just tune it to a
good frequency. There are also kit and prebuilt 10 MHz receivers out
there in the $30-$40 range which will work. You accept a slight loss in
daily coverage by selecting a compromise frequency, but it's better than
nothing and independent of GPS.
If you (or anyone else on NANOG) needs some help getting the
audio refclocks working; drop me a line.
There used to be WWVB (60 KHz) receivers. The good ones phase locked
to the carrier. The general rise in EMI made those close to useless
in most locations. NIST finished the job when they changed the
modulation format a few years ago. As far as I know, there aren't any
replacements for the old gear that take advantage of the new modulation
format. GPS works too well.
It's not so much that GPS works so well, as there's no way to
produce a commercial receiver that uses the enhanced format. By gifting
the developed IP back to the developer as part of the SIPR grant, it is
all sitting under a patent umbrella. Unfortunately, the startup that
developed it appears to have failed (at least, they've mostly vanished,
folks seem to have moved on, and they're late on corporate reports at
this point.) -- leaving the new format only usable by hackers and not
something that can be rolled into a commercial timing receiver.
My biggest beef with the new format was the rollout, 5 years ago
now, before a commercial receiver was available on the market. I'm not
sure why NIST has stuck with it.
There are some boxes that recover the time from nearby cell phone towers. I
think they will stop working as the towers get upgraded to the newer
protocols that use a different form of timing. That will probably take many
years. But the cell phone towers depend on GPS. (You can ususlly spot the
conical antenna(s) if you look around a bit.)
CDMA was only ever good to +/- 10ms anyway, at least any of the
boxes I ever used. You can actually outperform it with classic WWV or CHU,
and those get you a real backup, rather than an indirect dependancy on
GPS.
--msa