Note to all;

Be cautious about getting time of day from consumer GPS products.  All that
I have encountered
(so far) exhibit T.O.D. errors up to a few tenths of a second, and the
error is not repeatable from
session to session.  Some do have PPS outputs, which are typically claimed
to provide usec
level of accuracy, but most do not.

I routinely use WWV to verify correct setting of my WWVB-synced watch and
kitchen clock.  I have
occasionally seen severe setting errors, which I attribute to attempts at
syncing in the face of poor
WWVB reception conditions.

My impression is that none of the time codes currently in use by broadcast
NIST time signals
contain forward error correction or even error detection features.  If this
is wrong, please somebody
correct me!

BTW, there are a fair number of Heathkit clocks in the wild which use WWV
(as opposed to WWVB)
for syncing.  An old college-era housemate with whom I keep in touch owns
and still uses at least
one of them.

Dana

On Mon, Aug 13, 2018 at 5:25 AM, Mark Spencer mark@alignedsolutions.com
wrote:

Hi

… but there are modules out there for not a lot of money that do indeed give
quite good PPS (and TOD) information. Picking out the good brands / models
from the junk is part of why you have lists like this one.

I believe you will find that the “new” PSK modulation scheme on WWVB has at
least some error detection built into it.

There aren’t a lot of those left running these days …..

Bob

On 8/12/18 8:40 AM, Craig Kirkpatrick wrote:

WWV/WWVH also provides HF propagation forecasts, severe weather warnings
for mariners, etc., as well as being a propagation beacon.

I don't think HF communications is completely going away - it's unique
in not requiring any infrastructure to achieve world-wide communications
other than the two endpoints of the link.

It's probably a smaller population than radio amateurs, but there are
people who work with HF propagation on a day to day basis. For example,
if Rocketlabs ever gets their act together and launches a couple more
rockets, I'll have a spacecraft in LEO for which I intend to use WWV and
WWVH as calibration sources.

Hello to the group. The Chronverter is now available again. US $37.
Its from unusual electronics as was mentioned earlier in the thread.
No matter how 2019 actually goes its a good way to keep the wwvb clocks
going.
Saves me from having to create the same thing.
Regards
Paul
WB8TSL

On Mon, Aug 13, 2018 at 8:39 AM, jimlux jimlux@earthlink.net wrote:

On 8/12/18 6:36 PM, David I. Emery wrote:

GPS is up high enough that aerodrag isn't really a problem - if you're
above 1500km, it's negligible, and they're up at 20,000km.
Solar wind pressure will push them around a bit, but not much.  I would
think that if you did nothing, they'll be there for a very, very long time.

Their orbit is actually a quite high radiation zone (traversing the
radiation belts as they pass through the polar region), compared to GEO.

So the GPS satellites are pretty robust to this kind of thing.

Hi

Ok, this is Time Nuts. We probably have a pretty good sample of those who use this and that as a source of time.
We also are reasonably conscious about what we are doing. NIST’s claimed reason for running WWV (and WWVH) is to
distribute accurate time and frequency.

Would / does anybody on the list actually use WWV as their primary source of accurate time or accurate frequency?

Ok, so how about as a secondary source of time?

Now show of hands …. third tier backup?

I’ll place my votes first …. rarely as a third tier backup. Why? It’s just not good enough any more compared to the other
things I have easily available.

No, I”m not debating how badly we need third or eight tier backups. The question is purely - what is it actually used for?

Bob

I'll just add:

I got into time nuts after I acquired a GPSDO for checking the frequency accuracy of my amateur radios.  I realized I needed a GPSDO when I couldn't figure out if I was seeing drift in my radios frequency standards or Doppler shift from WWV transmissions while using WWV as a frequency reference.

To recap a prior post I do use WWV fairly often as a time source (mostly when I am in "the field") and I have occasionally used WWV as a frequency standard (not withstanding my concerns about Doppler shift.)  All of this is for non commercial / hobby use.

Mark Spencer

Aligned Solutions Co.
mark@alignedsolutions.com
604 762 4099

On Mon, Aug 13, 2018 at 8:10 AM, Bob kb8tq kb8tq@n1k.org wrote:

I've never posted here and am mindful of the S/N ratio message sent
out this morning but I am glad to see a post like this.

I would be very sad if I could not tune to 10,000,000.000 000 Hz
(usually, but the others occasionally, too, though I haven't copied
the new/old 25-MHz beacon yet) and hear the reassuring beat of WWV.
Given all the garbage on most of the radio bands, amateur or
professional, especially MW, WWV's programming is about the best out
there.

But I don't use them for time.  Everything at work is NTP with three
Symmetricom (yep, just old enough) S100s disciplining a set of servers
that users aim at.  Occasionally, someone fusses about "needing" PTP
for something or other "because it's better" until we start mentioning
the cost of the hardware and they suddenly decide that NTP is more
than enough.  Yes, NTP relies on GPS (and I guess the other GNSSs
these days) for the most part but there are other sources of time out
there that are not GPS based.  Dave Mills, W3HCF, included hooks for
WWV receivers in the NTP reference implementation on which most NTP
clients are based, but in all the years I've tinkered with NTP, I
don't ever remember seeing a Stratum 1 advertising that it's
disciplined by WWV.

Some buildings where I work have Primex master clock systems - GPS
receiver -> 72-MHz transmitter -> battery-powered wall clocks.  Some
clocks don't get a good signal but that's more a function of who
positioned the master clock (not me!) than a fault with the system
itself.

WWV/WWVH/WWVB never enters into the picture anywhere on campus AFAIK.

As for voters suddenly marching on their Congressmen's office because
their WWVB-disciplined clock no longer keeps time let me ask this: if
WWVB stopped transmitting how many people who have "atomic clocks"
would 1) notice 2) understand that the atomic clock is actually
elsewhere, and 3) that the timecode is sent from a government radio
station on 60 kHz?  Most would just say "ah, it's busted" and throw it
out.

I have yet to hear anyone make a case for retaining the HF system that
isn't backed by nostalgia.

As for solar flares taking out the various GNSSs ... wouldn't a solar
flare only take out the vehicles that were on the "sunny" side of the
Earth?  Wouldn't the (approximately) half of the SVs that are in the
Earth's shadow be unaffected?  Serious technical question - I have no
idea.

--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!

On 8/13/18 6:10 AM, Bob kb8tq wrote:

I don't use WWV (or WWVH) as a source of time/frequency per-se - what I
use it for is as a beacon at a known power, frequency, and antenna
pattern, with (presumably) very good close in phase noise.

The ionosphere has a coherence time of a few seconds, so ADEV of the
source at tau of 10 sec or longer isn't a huge thing for me.  But that 1
Hz/1 sec time frame is of real interest.

As the receiver flies over, we get nice soundings "through" the
ionosphere with good performance in the short term.

The usual ionosondes don't have anywhere near the same carrier purity,
and, because they sweep, you have to have good time synchronization of
your super het receiver to make sure you can tune the signal.

With WWV, I can set my center frequency to, say, 10.005 MHz, record 25
kHz BW for several minutes as I fly over and make my measurements.  The
"phase noise and ADEV" of my receiver position is very small - zipping
along 500 km at the top of the ionosphere, there's not a lot of bumps in
the road, so it's easy to model the position.

Not for my current spacecraft, but for a future one (SunRISE), we'll be
measuring (post processed) spacecraft position and time to a few ns.
The current one isn't that good - but for this one, we're interested in
the lumps and bumps of the ionosphere, and that's a "over time spans of
<3 seconds" kind of measurement.

That said, if WWV were to turn off tomorrow, I could probably build a
ground beacon with adequate performance to do my science. I don't need
kilowatts of radiated power - it's just convenient that WWV exists and
someone else does it. And in reality, I'd rather have an antenna which
radiates more "up" than "out" - WWV and WWVH are vertical dipoles - good
for skywave propagation, not so hot for vertical sounding.

On 8/13/18 6:52 AM, Peter Laws wrote:

Actually, it's the particles associated with the solar flare that cause
the problem, and they move substantially slower than the speed of light
(it takes hours to days), and they spread out a lot in time.

There's a plot at the wikipedia page on flares

https://en.wikipedia.org/wiki/Solar_flare#/media/File:ExtremeEvent_20120304-00h_20120317-24h.jpg

You can see the proton flux is spread out over many hours

(I'm project manager for constellation of satellites we're going to
fly to do radio interferometry imaging of the sun at HF for Coronal Mass
Ejections.. time tags are important to us)