I"m trying to build a clock that uses the WWVB signal to keep its own
time.  I have everything built and working except the Antenna portion.
I have a 1.1mH ferrite rod Antenna.
I know tuning it would require a capacitor that I calculated to be
7700pF.  The problem I am having is tuning it.  I am not sure how to
test it to make sure it is working correctly.  I have tried
broadcasting a 60kHz signal from a function generator and viewing it on
an O-scope and Spectrum Analyzer, but I"m seeing nothing.  I"m looking
for any suggestions to prove I have this tuned correctly.  

THanks

Hello,

On Thu, Apr 13, 2006 at 06:52:11PM -0700, bgjim225 wrote:
> I"m trying to build a clock that uses the WWVB signal to keep its own
> time.  I have everything built and working except the Antenna portion.
> I have a 1.1mH ferrite rod Antenna.
> I know tuning it would require a capacitor that I calculated to be
> 7700pF.  The problem I am having is tuning it.  I am not sure how to
> test it to make sure it is working correctly.  I have tried
> broadcasting a 60kHz signal from a function generator and viewing it on
> an O-scope and Spectrum Analyzer, but I"m seeing nothing.  I"m looking
> for any suggestions to prove I have this tuned correctly.  

Do you have a schematic of the receiver you are trying to use? The 
problem can be almost anywhere.

Regards

Francesco  IS0FKQ
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"bgjim225" <bgjim225@yahoo.com> wrote
> I"m trying to build a clock that uses the WWVB signal to keep its own
> time.  I have everything built and working except the Antenna portion.
> I have a 1.1mH ferrite rod Antenna.
> I know tuning it would require a capacitor that I calculated to be
> 7700pF.  The problem I am having is tuning it.  I am not sure how to
> test it to make sure it is working correctly.  I have tried
> broadcasting a 60kHz signal from a function generator and viewing it on
> an O-scope and Spectrum Analyzer, but I"m seeing nothing.  I"m looking
> for any suggestions to prove I have this tuned correctly.

Look for the Temic U4221B datasheet. Also 
http://www.c-maxgroup.com/tech/antenna.php may be helpful.

Karel Sandler 

bgjim225 wrote:
> I"m trying to build a clock that uses the WWVB signal to keep its own
> time.  I have everything built and working except the Antenna portion.
> I have a 1.1mH ferrite rod Antenna.
> I know tuning it would require a capacitor that I calculated to be
> 7700pF.  The problem I am having is tuning it.  I am not sure how to
> test it to make sure it is working correctly.  I have tried
> broadcasting a 60kHz signal from a function generator and viewing it on
> an O-scope and Spectrum Analyzer, but I"m seeing nothing.  I"m looking
> for any suggestions to prove I have this tuned correctly.  

I don't know of any simple way to tune other than what you're trying 
(using a signal generator and receiver).  Depending on the Q of the 
inductor, the resonance might be very sharp and you may need to tune 
quite a distance around 60kHz to find it -- particularly if your signal 
generator calibration is questionable.  Also, be careful that you don't 
load the antenna as you try to couple signal into it.

Another thought -- how are you impedance matching from the antenna to 
the receiver?  Depending on design, a loop may be a high impedance and 
loading it with 50 ohms may not work too well.  The shielded loop 
antenna I built (http://www.febo.com/time-freq/wwvb/antenna/index.html) 
used a 1 turn loop intertwined with the tuned loop to transform the 
impedance down to a more usable level.

John
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This sounds like great information for

 http://ntp.isc.org/bin/view/Support/ConfiguringWWVRefclocks

if y'all would care to add that info there...

H

Speaking of which, if I created WWVRefclockUsers, would anybody add
themselves to that list?

(I don't need to be the one to create it, but I will if nobody else does.)

H

Harlan Stenn said the following on 04/14/2006 08:58 PM:
> Speaking of which, if I created WWVRefclockUsers, would anybody add
> themselves to that list?
> 
> (I don't need to be the one to create it, but I will if nobody else does.)

Harlan, you might want to distinguish between WWV (HF) and WWVB (LF)
users.  I'd add myself to the WWVB list, and will be happy to add a link
to my WWVB-related pages.

John

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Harlan Stenn said the following on 04/14/2006 08:58 PM:
>> Speaking of which, if I created WWVRefclockUsers, would anybody add
>> themselves to that list?

John Ackermann said:
> Harlan, you might want to distinguish between WWV (HF) and WWVB (LF)
> users.  I'd add myself to the WWVB list, and will be happy to add a link
> to my WWVB-related pages.

OK, I have created pages for WWV and WWVB refclock configuration and users.

H

Speaking of WWVB clocks: does any company actually manufacture a
preconfigured WWVB clock with a serial interface anymore? I've been
unable to find one. Spectracom and the other manufacturers that used to
make them seem to have switched over to GPS entirely.

The reason I ask is I'd like to set up a refclock at my employer's HQ,
but the datacenter is in the 10th floor of a 50-floor high rise. The
building is closely surrounded by others with similar or greater
height. I can't use GPS becuase none of the windows open, renting roof
space is not possible, and I cannot get any GPS signal through the
windows. The location is basically the worst "urban canyon" scenario
you can imagine .

I'm 1462.5 km (4.8 ms) from the WWVB transmitters, which is well inside
the coverage area maps on the NIST site. I figure WWVB is my best
(only?) option for a refclock at this location. Is sub-milisecond
accuracy possible using a WWVB refclock? The NIST site says 0.1 to 15
ms phase error, which is two orders of magnitude. I see ~5 ms average
offsets when I sync with nearby stratum-1 servers via NTP. Would WWVB
perform any better?

I'd rather not build a WWVB receiver and antenna if I can just buy one
for use with NTP.

>The reason I ask is I'd like to set up a refclock at my employer's HQ,
>but the datacenter is in the 10th floor of a 50-floor high rise. The
>building is closely surrounded by others with similar or greater
>height. I can't use GPS becuase none of the windows open, renting roof
>space is not possible, and I cannot get any GPS signal through the
>windows. The location is basically the worst "urban canyon" scenario
>you can imagine .

>I'm 1462.5 km (4.8 ms) from the WWVB transmitters, which is well inside
>the coverage area maps on the NIST site. I figure WWVB is my best
>(only?) option for a refclock at this location. Is sub-milisecond
>accuracy possible using a WWVB refclock? The NIST site says 0.1 to 15
>ms phase error, which is two orders of magnitude. I see ~5 ms average
>offsets when I sync with nearby stratum-1 servers via NTP. Would WWVB
>perform any better?

I'm not a wizard on this topic.

I think WWVB has significant variation on propagation delays over
the day.  You can probably get good accuracy if you have a good
crystal and are willing to average over a week or so.

I don't know of any box that does that.  The normal PC crystal
is not very good on this scale so you can't do the averaging
from withing NTP. At least not if you NTP server is in a house
like mine.  Maybe you can if you have good air conditioning.

Do cell phones work in your offices?  If so, there is at least
one company making NTP boxes that work off cell phone timing which
is basically a relay from GPS.

Google for >CDMA NTP<.  This is the one that I remember:
  http://www.endruntechnologies.com/tempus-ntp-server.htm
(I have no idea if their gear is any good.  It's out of my
hobby price range.)



-- 
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other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.

Ry said the following on 04/15/2006 02:14 AM:

> I'm 1462.5 km (4.8 ms) from the WWVB transmitters, which is well inside
> the coverage area maps on the NIST site. I figure WWVB is my best
> (only?) option for a refclock at this location. Is sub-milisecond
> accuracy possible using a WWVB refclock? The NIST site says 0.1 to 15
> ms phase error, which is two orders of magnitude. I see ~5 ms average
> offsets when I sync with nearby stratum-1 servers via NTP. Would WWVB
> perform any better?

I can't answer your question about current availability, but I can show
you some WWVB results.  I have an old Spectracom 8170 and the
accompanying large ferrite antenna is mounted on my roof.  I'm about
1770km from the station.

At http://www.febo.com/time-freq/ntp/stats/index.html I have a set of
plots derived from the peerstats file of one of my NTP servers,
databox.febo.com.  It shows the offset of my other internal NTP boxes,
as well as three external stratum 1s, versus the system time (ie, the
offset field from peerstats).  databox itself is a stratum 1 machine,
using a shared memory PPS driver to sync to an HP Z3801A GPS disciplined
oscillator.  So the offset of the other servers is being measured
against a fairly stable baseline, and if you're sneaky you can back out
any wander in databox's time by looking at common-mode wiggles in the
plots.

(Unfortunately, at the moment I'm doing some reconfiguration and two of
the servers that should be stratum 1 are actually running at stratum 2,
and one of them has a very strange wander pattern over 5ms or so that
makes the rest of the plot harder to read than it should be; all the
other machines are typically grouped well within 1ms.)

In general, toe.febo.com, which is hooked to the Spectracom 8170, holds
within several hundred microseconds of the other clocks.  However, every
now and then, perhaps once every couple of weeks, there is a downward
excursion of perhaps 20ms and a recovery that takes a couple of days to
fully complete.  I suspect this occurs when the 8170 loses lock and its
 10MHz oscillator goes into free-run mode for a little while.  It may be
that a receiver alignment would reduce the magnitude of this effect, but
my longer term plans are to use an external reference oscillator.

So, other than that occasional anomaly, the WWVB receiver provides very
good time, usually well within 1ms.

By the way -- I also have some plots of WWVB received signal strength at
http://www.febo.com/time-freq/wwvb/sig-strength/index.html, comparing
the performance of a couple of antennas, and showing the strength change
from day to night.

Having said all that, I think you may have problems getting decent
reception if your WWVB antenna is in a machine room near the bottom of
an urban canyon, but it's worth a shot.  Another thing you might
consider is one of the CDMA refclocks that get their time from the
cellular network.  It won't be as traceable as using an NIST or USNO
source, but you shouldn't have trouble getting a signal.

John

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Propably its just better to get a cheap SpectrumAnalyzer? Just look at:
http://test1.contenttest.net/Spektrumanalysator_en.shtml
They have realy cool equipment at VERY low price...

Hal Murray wrote:
> Do cell phones work in your offices?  If so, there is at least
> one company making NTP boxes that work off cell phone timing which
> is basically a relay from GPS.

This only works for CDMA call phone systems, Endrun knows where.
> 
> Google for >CDMA NTP<.  This is the one that I remember:
>   http://www.endruntechnologies.com/tempus-ntp-server.htm
> (I have no idea if their gear is any good.  It's out of my
> hobby price range.)

I have one such unit installed in Tampa. It is quite pricey ($1100 ?), 
but it does seem to work, except that it has needed a 
reset/reconfiguration for a few months, and I don't have anyone locally 
who can handle it. :-(

Terje

-- 
- <Terje.Mathisen@hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"

Ry wrote:

> Speaking of WWVB clocks: does any company actually manufacture a
> preconfigured WWVB clock with a serial interface anymore? I've been
> unable to find one. Spectracom and the other manufacturers that used to
> make them seem to have switched over to GPS entirely.
>


WWVB Receivers are occasionally available on e-Bay for $100 - $300.

<snip>
> 
> I'm 1462.5 km (4.8 ms) from the WWVB transmitters, which is well inside
> the coverage area maps on the NIST site. I figure WWVB is my best
> (only?) option for a refclock at this location. Is sub-milisecond
> accuracy possible using a WWVB refclock? 

Possible?  Yes.  Probable?  No!  If you want to invest about $35 in an 
"atomic clock" You can hang it on your wall and check the reception 
indication several times during the work day.  If you get solid 
reception during daylight hours a WWVB receiver just might give you 
sub-millisecond accuracy.  If you lose signal during daylight hours, 
forget it!

> The NIST site says 0.1 to 15
> ms phase error, which is two orders of magnitude. I see ~5 ms average
> offsets when I sync with nearby stratum-1 servers via NTP. Would WWVB
> perform any better?
> 
> I'd rather not build a WWVB receiver and antenna if I can just buy one
> for use with NTP.
> 

I never had a WWVB receiver to try it with.  If someone wants to lend me 
some equipment I'll compare it with my GPS refclock.

On Sat, 15 Apr 2006 09:33:49 -0400, Richard B. Gilbert wrote:

> Possible?  Yes.  Probable?  No!  If you want to invest about $35 in an 
> "atomic clock" You can hang it on your wall and check the reception 
> indication several times during the work day.  If you get solid 
> reception during daylight hours a WWVB receiver just might give you 
> sub-millisecond accuracy.  If you lose signal during daylight hours, 
> forget it!

Except the clocks use very simplistic methods for decoding the signal.
Something not to dissimilar to the current versions of radioclkd. However
you can do much better than this.

If you employ some advanced (well not that advanced really but it looks
very impressive) statistical filtering to the signal you can still decode
a signal when the basic methods fail utterly. I know the clocks are not
doing this because it would require way more CPU power than the
micro-controllers in them have.


JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

Jonathan Buzzard wrote:
> On Sat, 15 Apr 2006 09:33:49 -0400, Richard B. Gilbert wrote:
> 
> 
>>Possible?  Yes.  Probable?  No!  If you want to invest about $35 in an 
>>"atomic clock" You can hang it on your wall and check the reception 
>>indication several times during the work day.  If you get solid 
>>reception during daylight hours a WWVB receiver just might give you 
>>sub-millisecond accuracy.  If you lose signal during daylight hours, 
>>forget it!
> 
> 
> Except the clocks use very simplistic methods for decoding the signal.
> Something not to dissimilar to the current versions of radioclkd. However
> you can do much better than this.
> 
> If you employ some advanced (well not that advanced really but it looks
> very impressive) statistical filtering to the signal you can still decode
> a signal when the basic methods fail utterly. I know the clocks are not
> doing this because it would require way more CPU power than the
> micro-controllers in them have.
> 
> 
> JAB.
> 

Does anyone still make this sort of hardware?  Other than the occasional 
antiques available on e-Bay, I have not heard of any.

John, et al,

You are not going to like this.

I;ve been running several WWVB clocks since 1981 using Spectracom 8170 
and Netclock/2 receivers with the NTP WWVB driver. NIST Time and 
Frequency Services, NIST Special Publication 462 (Revised 1990), claims 
nominal timecode accuracy of 100 microseconds, and that's what I got in 
the beginning.

The WWVB signal has become degraded in recent years and now all WWVB 
receivers here have been retired. Here in Delaware we are on the 100 
microvolt per meter contour (before the WWVB transmitter upgrade) and 
normally this would be sufficient for good accuracy. However, at least 
here in Newark, there is another strong signal on 60 kHz that interferes 
with WWVB. I chased this down to power-line conducted EMI and found the 
interferiing signal was well above the noise several miles from campus. 
It's not clear where it originates, but the prime suspect is a power 
inverter for an arc welder at the Chrysler plant in town.

This was bad enough, but then we started installing banks of UPS units 
in the machine room and they scream like banshees on 60 kHz, even with 
the antenna on the roof of an outbuilding. The result was total failure 
of all our WWVB radios, at least on campus.

Until recently I was getting good results at home, but now I see the 
signal has failed there as well, probably due to increased crud at 60 
kHz due some incidental radiator. I conclude WWVB is no longer useful 
here and I suspect in any machine room, unless the antenna is far away 
from the UPSes and with suitable ferrite decoupling.

A solution that would probably work for business is to locate the 
antenna and radio in a doghouse on the roof and run serial cable to the 
machine room. Lemme tell you how hard that is with a plastic sheet roof 
and a landlord that believes rooftop space rental for tenant machinery 
is a significant revenue stream.

Dave

John Ackermann N8UR wrote:
> Ry said the following on 04/15/2006 02:14 AM:
> 
> 
>>I'm 1462.5 km (4.8 ms) from the WWVB transmitters, which is well inside
>>the coverage area maps on the NIST site. I figure WWVB is my best
>>(only?) option for a refclock at this location. Is sub-milisecond
>>accuracy possible using a WWVB refclock? The NIST site says 0.1 to 15
>>ms phase error, which is two orders of magnitude. I see ~5 ms average
>>offsets when I sync with nearby stratum-1 servers via NTP. Would WWVB
>>perform any better?
> 
> 
> I can't answer your question about current availability, but I can show
> you some WWVB results.  I have an old Spectracom 8170 and the
> accompanying large ferrite antenna is mounted on my roof.  I'm about
> 1770km from the station.
> 
> At http://www.febo.com/time-freq/ntp/stats/index.html I have a set of
> plots derived from the peerstats file of one of my NTP servers,
> databox.febo.com.  It shows the offset of my other internal NTP boxes,
> as well as three external stratum 1s, versus the system time (ie, the
> offset field from peerstats).  databox itself is a stratum 1 machine,
> using a shared memory PPS driver to sync to an HP Z3801A GPS disciplined
> oscillator.  So the offset of the other servers is being measured
> against a fairly stable baseline, and if you're sneaky you can back out
> any wander in databox's time by looking at common-mode wiggles in the
> plots.
> 
> (Unfortunately, at the moment I'm doing some reconfiguration and two of
> the servers that should be stratum 1 are actually running at stratum 2,
> and one of them has a very strange wander pattern over 5ms or so that
> makes the rest of the plot harder to read than it should be; all the
> other machines are typically grouped well within 1ms.)
> 
> In general, toe.febo.com, which is hooked to the Spectracom 8170, holds
> within several hundred microseconds of the other clocks.  However, every
> now and then, perhaps once every couple of weeks, there is a downward
> excursion of perhaps 20ms and a recovery that takes a couple of days to
> fully complete.  I suspect this occurs when the 8170 loses lock and its
>  10MHz oscillator goes into free-run mode for a little while.  It may be
> that a receiver alignment would reduce the magnitude of this effect, but
> my longer term plans are to use an external reference oscillator.
> 
> So, other than that occasional anomaly, the WWVB receiver provides very
> good time, usually well within 1ms.
> 
> By the way -- I also have some plots of WWVB received signal strength at
> http://www.febo.com/time-freq/wwvb/sig-strength/index.html, comparing
> the performance of a couple of antennas, and showing the strength change
> from day to night.
> 
> Having said all that, I think you may have problems getting decent
> reception if your WWVB antenna is in a machine room near the bottom of
> an urban canyon, but it's worth a shot.  Another thing you might
> consider is one of the CDMA refclocks that get their time from the
> cellular network.  It won't be as traceable as using an NIST or USNO
> source, but you shouldn't have trouble getting a signal.
> 
> John
> 
> _______________________________________________
> questions mailing list
> questions@lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions
> 

>The WWVB signal has become degraded in recent years and now all WWVB 
>receivers here have been retired. Here in Delaware we are on the 100 
>microvolt per meter contour (before the WWVB transmitter upgrade) and 
>normally this would be sufficient for good accuracy. However, at least 
>here in Newark, there is another strong signal on 60 kHz that interferes 
>with WWVB. I chased this down to power-line conducted EMI and found the 
>interferiing signal was well above the noise several miles from campus. 
>It's not clear where it originates, but the prime suspect is a power 
>inverter for an arc welder at the Chrysler plant in town.

I'm not a wizard at this stuff.  CPUs are cheap these days.

Would it be possible to pull the signal out of the junk
with some serious DSP hacking?

At the back of an envelope level, how would one answer
that question?

On the other hand, NIST recently upgraded the transmitter
at WWVB, so somebody must think this is a valuable service.
Do they have anybody tracking the EMI issues?

Who uses WWVB these days?  Have serious time hackers all switched
to GPS, leaving "atomic clocks" as the only customer?

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other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.

Hi Dave --

We've chatted about your WWVB problems in the past, and you seem to have
a real collection of noisemakers that cause problems.  On the other
hand, I get really good reception here in Ohio.  I'm using the
Spectracom ferrite antenna (with internal preamp) up on the roof of my
house, and don't have any major spark generators nearby.  I do, however,
have challenges of my own with a few AM broadcasters that put in very
strong signals.  The BCB power coming down the coax of my wideband LF
antenna is so great that my LORAN receiver shows a diurnal phase shift
when the broadcaster changes antenna pattern at sunrise and sunset.

I get very good signal strength, and the 8170 loses lock maybe once
every 10 days; I've never actually seen the "lock" LED go off when I was
there.

I just looked at the NIST WWVB page, and it looks like the experiment
they were doing with the modulation depth has become permanent -- the
advertised power drop is now 17dB instead of the 10dB it used to be.  I
wonder if that might have a negative effect on some users, particularly
if they are competing with a lot of local noise.

I guess from Dave's, and my, experience you can draw the conclusion that
WWVB reception quality may be very dependent on the local environment.

By the way -- despite my fondness for LF, I'll readily acknowledge that
GPS is certainly a better time source in a whole bunch of ways, as long
as you can see the sky.

John
----
David L. Mills said the following on 04/15/2006 11:31 PM:
> John, et al,
> 
> You are not going to like this.
> 
> I;ve been running several WWVB clocks since 1981 using Spectracom 8170
> and Netclock/2 receivers with the NTP WWVB driver. NIST Time and
> Frequency Services, NIST Special Publication 462 (Revised 1990), claims
> nominal timecode accuracy of 100 microseconds, and that's what I got in
> the beginning.
> 
> The WWVB signal has become degraded in recent years and now all WWVB
> receivers here have been retired. Here in Delaware we are on the 100
> microvolt per meter contour (before the WWVB transmitter upgrade) and
> normally this would be sufficient for good accuracy. However, at least
> here in Newark, there is another strong signal on 60 kHz that interferes
> with WWVB. I chased this down to power-line conducted EMI and found the
> interferiing signal was well above the noise several miles from campus.
> It's not clear where it originates, but the prime suspect is a power
> inverter for an arc welder at the Chrysler plant in town.
> 
> This was bad enough, but then we started installing banks of UPS units
> in the machine room and they scream like banshees on 60 kHz, even with
> the antenna on the roof of an outbuilding. The result was total failure
> of all our WWVB radios, at least on campus.
> 
> Until recently I was getting good results at home, but now I see the
> signal has failed there as well, probably due to increased crud at 60
> kHz due some incidental radiator. I conclude WWVB is no longer useful
> here and I suspect in any machine room, unless the antenna is far away
> from the UPSes and with suitable ferrite decoupling.
> 
> A solution that would probably work for business is to locate the
> antenna and radio in a doghouse on the roof and run serial cable to the
> machine room. Lemme tell you how hard that is with a plastic sheet roof
> and a landlord that believes rooftop space rental for tenant machinery
> is a significant revenue stream.
> 
> Dave

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My Cingular GSM phone works in the datacenter, so I imagine a CDMA
refclock might work for us.

But haven't most mobile phone carriers moved away from CDMA? Are
precise time signals still broadcast as part of the newer "spread
spectrum" 3G standards? (EV-DO seems to be based on CDMA at least in
part, but I'm not sure about GSM/UTMS). Would a CDMA refclock be a
short-term solution given the rollout of newer standards by the mobile
phone carriers?

I'll ask these same questions of vendors, of course, to discover how
"future-proof" their products are. But vendors are not likely to have
an unbiased view of the long-term viability of CDMA as a time source.

Thanks,
  Ry

Hal,

THe Spectracom receiver is actually very good. It can pull the signal 
from beneath the noise (literally), but doesn't do well with cochannel 
signals. What I saw on the scope was a substantial carrier modulated 
with 60-Hz square wave(!). That's why I suspect an arc welder. I called 
in the power company and they were quite cooperative (heck; they were 
hams themselves). It was easy to verify the crud quickly dived under the 
noise when more than a couple hundred feet from the power line. I could 
probably fix it at home with line filters.

Outboard DSP might help, but I would DC coupling and the only thing I 
have around for that is an old DSP93. Heck; not this year.

Dave

Hal Murray wrote:
>>The WWVB signal has become degraded in recent years and now all WWVB 
>>receivers here have been retired. Here in Delaware we are on the 100 
>>microvolt per meter contour (before the WWVB transmitter upgrade) and 
>>normally this would be sufficient for good accuracy. However, at least 
>>here in Newark, there is another strong signal on 60 kHz that interferes 
>>with WWVB. I chased this down to power-line conducted EMI and found the 
>>interferiing signal was well above the noise several miles from campus. 
>>It's not clear where it originates, but the prime suspect is a power 
>>inverter for an arc welder at the Chrysler plant in town.
> 
> 
> I'm not a wizard at this stuff.  CPUs are cheap these days.
> 
> Would it be possible to pull the signal out of the junk
> with some serious DSP hacking?
> 
> At the back of an envelope level, how would one answer
> that question?
> 
> On the other hand, NIST recently upgraded the transmitter
> at WWVB, so somebody must think this is a valuable service.
> Do they have anybody tracking the EMI issues?
> 
> Who uses WWVB these days?  Have serious time hackers all switched
> to GPS, leaving "atomic clocks" as the only customer?
> 

John,

Get a couple of nice big ferrite cores and take a couple of turns with 
your downlead. Also, I hope you are using the LORAN loop; the whip is 
far inferior. My Austron receivers have both failed and my homebrew 
LORAN works onlu pm ISA bus.

In the twenty years I have been here the RFI/EMI all over the LF, MF and 
HF bands has grown steadily worse. The W3UD ham radio club HF gear is 
essentially unusable.

Dave, w3hcf

John Ackermann N8UR wrote:

> Hi Dave --
> 
> We've chatted about your WWVB problems in the past, and you seem to have
> a real collection of noisemakers that cause problems.  On the other
> hand, I get really good reception here in Ohio.  I'm using the
> Spectracom ferrite antenna (with internal preamp) up on the roof of my
> house, and don't have any major spark generators nearby.  I do, however,
> have challenges of my own with a few AM broadcasters that put in very
> strong signals.  The BCB power coming down the coax of my wideband LF
> antenna is so great that my LORAN receiver shows a diurnal phase shift
> when the broadcaster changes antenna pattern at sunrise and sunset.
> 
> I get very good signal strength, and the 8170 loses lock maybe once
> every 10 days; I've never actually seen the "lock" LED go off when I was
> there.
> 
> I just looked at the NIST WWVB page, and it looks like the experiment
> they were doing with the modulation depth has become permanent -- the
> advertised power drop is now 17dB instead of the 10dB it used to be.  I
> wonder if that might have a negative effect on some users, particularly
> if they are competing with a lot of local noise.
> 
> I guess from Dave's, and my, experience you can draw the conclusion that
> WWVB reception quality may be very dependent on the local environment.
> 
> By the way -- despite my fondness for LF, I'll readily acknowledge that
> GPS is certainly a better time source in a whole bunch of ways, as long
> as you can see the sky.
> 
> John
> ----
> David L. Mills said the following on 04/15/2006 11:31 PM:
> 
>>John, et al,
>>
>>You are not going to like this.
>>
>>I;ve been running several WWVB clocks since 1981 using Spectracom 8170
>>and Netclock/2 receivers with the NTP WWVB driver. NIST Time and
>>Frequency Services, NIST Special Publication 462 (Revised 1990), claims
>>nominal timecode accuracy of 100 microseconds, and that's what I got in
>>the beginning.
>>
>>The WWVB signal has become degraded in recent years and now all WWVB
>>receivers here have been retired. Here in Delaware we are on the 100
>>microvolt per meter contour (before the WWVB transmitter upgrade) and
>>normally this would be sufficient for good accuracy. However, at least
>>here in Newark, there is another strong signal on 60 kHz that interferes
>>with WWVB. I chased this down to power-line conducted EMI and found the
>>interferiing signal was well above the noise several miles from campus.
>>It's not clear where it originates, but the prime suspect is a power
>>inverter for an arc welder at the Chrysler plant in town.
>>
>>This was bad enough, but then we started installing banks of UPS units
>>in the machine room and they scream like banshees on 60 kHz, even with
>>the antenna on the roof of an outbuilding. The result was total failure
>>of all our WWVB radios, at least on campus.
>>
>>Until recently I was getting good results at home, but now I see the
>>signal has failed there as well, probably due to increased crud at 60
>>kHz due some incidental radiator. I conclude WWVB is no longer useful
>>here and I suspect in any machine room, unless the antenna is far away
>>from the UPSes and with suitable ferrite decoupling.
>>
>>A solution that would probably work for business is to locate the
>>antenna and radio in a doghouse on the roof and run serial cable to the
>>machine room. Lemme tell you how hard that is with a plastic sheet roof
>>and a landlord that believes rooftop space rental for tenant machinery
>>is a significant revenue stream.
>>
>>Dave
> 
> 
> _______________________________________________
> questions mailing list
> questions@lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions
> 

My main LF antenna for other than WWVB is an AMRAD-design active voltage 
probe antenna, with a 1 meter whip and a fiercely linear front-end (the 
transistor runs with something like 70ma bias to keep distortion 
products down).  It actually works very well for LORAN, with strong 
signal strength and very low noise numbers.

The problem, though, is that the broadband power (measured on an HP 
3586C selective voltmeter, in broadband mode) is about -6dBm, changing 
to about -3dBm at night when the BCB antenna patterns change.  That high 
power level was apparently changing the operating parameters of the 
LORAN receiver front end, and when the power changed by 3dB at night, it 
caused about a 30ns phase shift.  Adding a low pass filter knocked the 
broadband power down by about 50dB, and solved the problem.

I recently got an official Austron loop antenna of eBay, and plan to get 
that installed outside this summer.  But with the BCB filter in place, 
the AMRAD antenna does a really good job (and it's useful for other 
things as well -- I've also used it to receive WWVB).

73,
John
----

David L. Mills wrote:
> John,
> 
> Get a couple of nice big ferrite cores and take a couple of turns with 
> your downlead. Also, I hope you are using the LORAN loop; the whip is 
> far inferior. My Austron receivers have both failed and my homebrew 
> LORAN works onlu pm ISA bus.
> 
> In the twenty years I have been here the RFI/EMI all over the LF, MF and 
> HF bands has grown steadily worse. The W3UD ham radio club HF gear is 
> essentially unusable.
> 
> Dave, w3hcf
> 
> John Ackermann N8UR wrote:
> 
>> Hi Dave --
>>
>> We've chatted about your WWVB problems in the past, and you seem to have
>> a real collection of noisemakers that cause problems.  On the other
>> hand, I get really good reception here in Ohio.  I'm using the
>> Spectracom ferrite antenna (with internal preamp) up on the roof of my
>> house, and don't have any major spark generators nearby.  I do, however,
>> have challenges of my own with a few AM broadcasters that put in very
>> strong signals.  The BCB power coming down the coax of my wideband LF
>> antenna is so great that my LORAN receiver shows a diurnal phase shift
>> when the broadcaster changes antenna pattern at sunrise and sunset.
>>
>> I get very good signal strength, and the 8170 loses lock maybe once
>> every 10 days; I've never actually seen the "lock" LED go off when I was
>> there.
>>
>> I just looked at the NIST WWVB page, and it looks like the experiment
>> they were doing with the modulation depth has become permanent -- the
>> advertised power drop is now 17dB instead of the 10dB it used to be.  I
>> wonder if that might have a negative effect on some users, particularly
>> if they are competing with a lot of local noise.
>>
>> I guess from Dave's, and my, experience you can draw the conclusion that
>> WWVB reception quality may be very dependent on the local environment.
>>
>> By the way -- despite my fondness for LF, I'll readily acknowledge that
>> GPS is certainly a better time source in a whole bunch of ways, as long
>> as you can see the sky.
>>
>> John
>> ----
>> David L. Mills said the following on 04/15/2006 11:31 PM:
>>
>>> John, et al,
>>>
>>> You are not going to like this.
>>>
>>> I;ve been running several WWVB clocks since 1981 using Spectracom 8170
>>> and Netclock/2 receivers with the NTP WWVB driver. NIST Time and
>>> Frequency Services, NIST Special Publication 462 (Revised 1990), claims
>>> nominal timecode accuracy of 100 microseconds, and that's what I got in
>>> the beginning.
>>>
>>> The WWVB signal has become degraded in recent years and now all WWVB
>>> receivers here have been retired. Here in Delaware we are on the 100
>>> microvolt per meter contour (before the WWVB transmitter upgrade) and
>>> normally this would be sufficient for good accuracy. However, at least
>>> here in Newark, there is another strong signal on 60 kHz that interferes
>>> with WWVB. I chased this down to power-line conducted EMI and found the
>>> interferiing signal was well above the noise several miles from campus.
>>> It's not clear where it originates, but the prime suspect is a power
>>> inverter for an arc welder at the Chrysler plant in town.
>>>
>>> This was bad enough, but then we started installing banks of UPS units
>>> in the machine room and they scream like banshees on 60 kHz, even with
>>> the antenna on the roof of an outbuilding. The result was total failure
>>> of all our WWVB radios, at least on campus.
>>>
>>> Until recently I was getting good results at home, but now I see the
>>> signal has failed there as well, probably due to increased crud at 60
>>> kHz due some incidental radiator. I conclude WWVB is no longer useful
>>> here and I suspect in any machine room, unless the antenna is far away
>>> from the UPSes and with suitable ferrite decoupling.
>>>
>>> A solution that would probably work for business is to locate the
>>> antenna and radio in a doghouse on the roof and run serial cable to the
>>> machine room. Lemme tell you how hard that is with a plastic sheet roof
>>> and a landlord that believes rooftop space rental for tenant machinery
>>> is a significant revenue stream.
>>>
>>> Dave
>>
>>
>>
>> _______________________________________________
>> questions mailing list
>> questions@lists.ntp.isc.org
>> https://lists.ntp.isc.org/mailman/listinfo/questions
>>
> 
> _______________________________________________
> questions mailing list
> questions@lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions
> 
> 

_______________________________________________
questions mailing list
questions@lists.ntp.isc.org
https://lists.ntp.isc.org/mailman/listinfo/questions

On Sat, 15 Apr 2006 19:25:54 -0400, Richard B. Gilbert wrote:

[SNIP]
> 
> Does anyone still make this sort of hardware?  Other than the occasional 
> antiques available on e-Bay, I have not heard of any.

No idea, but you can cheaply interface OEM boards, similar to the type
that go in clocks to the serial port of a computer and then decode the
signal. I run both a MSF and DCF77 clock using this technique here in the
UK. My design and software also works with WWVB.

    http://www.buzzard.me.uk/jonathan/radioclock.html

At the moment I am working on some new advanced statistical filtering of
the signal that should provide *much* better decoding with weak signals.
No promise on the timescale when it will be ready however.

At the moment it exists as a Matlab program that runs against a previously
recorded HBG signal, that I normally cannot decode reliably with the
simplistic methods. However the Matlab program can decode the signal
accurately better than 90% of the time. It will need converting into C and
made to work in real time to be useful however.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

Jonathan Buzzard wrote:
> At the moment it exists as a Matlab program that runs against a previously
> recorded HBG signal, that I normally cannot decode reliably with the
> simplistic methods. However the Matlab program can decode the signal
> accurately better than 90% of the time. It will need converting into C and
> made to work in real time to be useful however.
> 
> JAB.
> 

Normally I'd suggesting running the MatLab compiler which can convert it
to a binary but the overhead can be horrendous. I've done it but I don't
think you'd be happy with the time it would need to run your algorithm.

Danny
_______________________________________________
questions mailing list
questions@lists.ntp.isc.org
https://lists.ntp.isc.org/mailman/listinfo/questions

Danny Mayer wrote:
> Jonathan Buzzard wrote:
> 
>>At the moment it exists as a Matlab program that runs against a previously
>>recorded HBG signal, that I normally cannot decode reliably with the
>>simplistic methods. However the Matlab program can decode the signal
>>accurately better than 90% of the time. It will need converting into C and
>>made to work in real time to be useful however.
>>
>>JAB.
>>
> 
> 
> Normally I'd suggesting running the MatLab compiler which can convert it
> to a binary but the overhead can be horrendous. I've done it but I don't
> think you'd be happy with the time it would need to run your algorithm.
> 
> Danny
> _______________________________________________
> questions mailing list
> questions@lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions
> 
If the difficulty is that the Matlab code is higly vectorizedm try using 
the svmt library to provide vector operations in c++.  I've been pleased 
with the ease of recoding Matlab radar processing code using it, but it 
is still recoding.  The svmt fft routine is pretty poor, thugh.  I 
hacked in a call to the fftw3 library implementation instead.  Matlab 
uses fftw3 for fft's as well.
Tim keck

Hello Jonathan,

 On Monday, April 17, 2006 at 18:33:50 +0100, Jonathan Buzzard wrote:

> http://www.buzzard.me.uk/jonathan/radioclock.html
> At the moment I am working on some new advanced statistical filtering
> of the signal that should provide *much* better decoding with weak
> signals. No promise on the timescale when it will be ready however.

Have you seen the noisy signal decoding scheme of Poul-Henning Kamp? He
published code for the DCF77 signal on the ntp-hackers list last
February. It seems to me promising and very cheap.
http://lists.ntp.isc.org/pipermail/hackers/2006-February/001934.html


Serge.
-- 
Serge point Bets arobase laposte point net

On Thu, 20 Apr 2006 12:37:04 +0200, Serge Bets wrote:

> Hello Jonathan,
> 
>  On Monday, April 17, 2006 at 18:33:50 +0100, Jonathan Buzzard wrote:
> 
>> http://www.buzzard.me.uk/jonathan/radioclock.html
>> At the moment I am working on some new advanced statistical filtering
>> of the signal that should provide *much* better decoding with weak
>> signals. No promise on the timescale when it will be ready however.
> 
> Have you seen the noisy signal decoding scheme of Poul-Henning Kamp? He
> published code for the DCF77 signal on the ntp-hackers list last
> February. It seems to me promising and very cheap.
> http://lists.ntp.isc.org/pipermail/hackers/2006-February/001934.html
> 

Interesting but what I am aiming at is something much more sophisticated.
The basics are I am using Bayesian statistics. That is I take a prior
which is what I think the transitions from 0 to 1 and 1 to 0 should be
occurring based on the current time on the computer.

I then feed in the measured transitions, which I use to update my prior
and out pops the result. I can do this every second, every two seconds,
every three seconds etc. down to every minute depending on how much CPU
time I wish to expend on the task. Oh and it's proper Bayesian statistics
I am using, not some thing else dressed up as being Bayesian as seems to
happen far to often.

The only problem at the moment (apart from being written in Matlab) is
that it does require your computers clock to be close to UTC to begin
with. If you are more than a second or so out that it does
not work very well.

I also need to test it on something more than a particular 24hour period
of the HBG signal that I captured last August. My normal code won't decode
the HBG signal where I live, just too far from the transmitter.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

On Tue, 18 Apr 2006 02:19:58 +0000, Danny Mayer wrote:

> Jonathan Buzzard wrote:
>> At the moment it exists as a Matlab program that runs against a previously
>> recorded HBG signal, that I normally cannot decode reliably with the
>> simplistic methods. However the Matlab program can decode the signal
>> accurately better than 90% of the time. It will need converting into C and
>> made to work in real time to be useful however.
>> 
>> JAB.
>> 
> 
> Normally I'd suggesting running the MatLab compiler which can convert it
> to a binary but the overhead can be horrendous. I've done it but I don't
> think you'd be happy with the time it would need to run your algorithm.
> 

I would not be happy with the resultant code. Using Matlab is purely an
algorithm development tool. Once I am happy with the algorithm I will
rewrite it in C.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

Jonathan,

I've been down the fancy decoding path myself, e.g., the WWV driver, 
which is a theoretically optimum linear receiver. However, much of the 
crud found at WWVB and DCF77 frequencies is bursty, which is what my 
LORAN-C receiver and program is good for. The Spectracom receiver is 
actually quite good: however, it was designed to cope with Gaussian 
noise, not suffer a 20-dB clobber by an interfering buzzsaw signal.

My precerred approach, should I accept the assignement, would be to tap 
onto the I and Q baseband signals in the radio, chop at something like 
10 kHz and feed to the L and R inputs on a sound card. I can take it 
from there. My problemis that the SNR has become so degraded that the 
very good PLL in the radio doesn't lock up.

Dave

Jonathan Buzzard wrote:

> On Tue, 18 Apr 2006 02:19:58 +0000, Danny Mayer wrote:
> 
> 
>>Jonathan Buzzard wrote:
>>
>>>At the moment it exists as a Matlab program that runs against a previously
>>>recorded HBG signal, that I normally cannot decode reliably with the
>>>simplistic methods. However the Matlab program can decode the signal
>>>accurately better than 90% of the time. It will need converting into C and
>>>made to work in real time to be useful however.
>>>
>>>JAB.
>>>
>>
>>Normally I'd suggesting running the MatLab compiler which can convert it
>>to a binary but the overhead can be horrendous. I've done it but I don't
>>think you'd be happy with the time it would need to run your algorithm.
>>
> 
> 
> I would not be happy with the resultant code. Using Matlab is purely an
> algorithm development tool. Once I am happy with the algorithm I will
> rewrite it in C.
> 
> JAB.
> 

On Fri, 21 Apr 2006 21:11:07 +0000, David L. Mills wrote:

> Jonathan,
> 
> I've been down the fancy decoding path myself, e.g., the WWV driver, 
> which is a theoretically optimum linear receiver. However, much of the 
> crud found at WWVB and DCF77 frequencies is bursty, which is what my 
> LORAN-C receiver and program is good for. The Spectracom receiver is 
> actually quite good: however, it was designed to cope with Gaussian 
> noise, not suffer a 20-dB clobber by an interfering buzzsaw signal.
> 
> My precerred approach, should I accept the assignement, would be to tap 
> onto the I and Q baseband signals in the radio, chop at something like 
> 10 kHz and feed to the L and R inputs on a sound card. I can take it 
> from there. My problemis that the SNR has become so degraded that the 
> very good PLL in the radio doesn't lock up.
>

But that requires a much more expensive receiver than a little OEM board
with short ferrite rod. So my algorithm is designed to work with what I
have which is just level transitions and times there of.


JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

Jonathan,

Understand the situation here has deteriorated to the point that I can't 
hear the signal at all with a good antenna and communications receiver. 
The signal is thorougly covered in wideband hash from the power line. A 
wee OEM board and loopstick simply won't cut it with any algorithm. The 
only way to do that may be to synchronoualy demodulate the I and Q 
components and use a state machine and maximum likelihood decoder 
similar to the algorithm used in the WWV driver.

Dave

Jonathan Buzzard wrote:

> On Fri, 21 Apr 2006 21:11:07 +0000, David L. Mills wrote:
> 
> 
>>Jonathan,
>>
>>I've been down the fancy decoding path myself, e.g., the WWV driver, 
>>which is a theoretically optimum linear receiver. However, much of the 
>>crud found at WWVB and DCF77 frequencies is bursty, which is what my 
>>LORAN-C receiver and program is good for. The Spectracom receiver is 
>>actually quite good: however, it was designed to cope with Gaussian 
>>noise, not suffer a 20-dB clobber by an interfering buzzsaw signal.
>>
>>My precerred approach, should I accept the assignement, would be to tap 
>>onto the I and Q baseband signals in the radio, chop at something like 
>>10 kHz and feed to the L and R inputs on a sound card. I can take it 
>>from there. My problemis that the SNR has become so degraded that the 
>>very good PLL in the radio doesn't lock up.
>>
> 
> 
> But that requires a much more expensive receiver than a little OEM board
> with short ferrite rod. So my algorithm is designed to work with what I
> have which is just level transitions and times there of.
> 
> 
> JAB.
>