[time-nuts] WWVB Clocks don't sync anymore (revisited) (J. Forster)
johncroos at aol.com
johncroos at aol.com
Wed Mar 20 13:55:17 EDT 2013
Re: WWVB Clocks don't sync anymore (revisited) (J. Forster)
As it turns out the batteries in my Radio Shack WWVB alarm clock had died. I replaced them last night
around midnight and went off to bed. This morning it has synched up fine. I dissected an identical
one of these a while back. It does have a very narrow band single resonator crystal filter. I think the
BW was just s few Hz and PSK would turn to AM at the keying rate. Of course on each phase reversal the
amplitude out of the filter would go to zero for an instant.
Here in East Kansas the WWVB signal from a ferrite rod can be received on my tek 475 with no premap.
That is loud.
-73 john K6iql
-----Original Message-----
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Today's Topics:
1. Re: WWVB Clocks don't sync anymore (revisited) (J. Forster)
2. Re: WWVB Clocks don't sync anymore (revisited) (J. Forster)
3. Re: Repair of PRS10 Lamp Assembly (Dr. G?tz Romahn)
4. Re: WWVB Clocks don't sync anymore (revisited) (Clint Turner)
5. Re: Is possible precise 1pps? (Herbert Poetzl)
----------------------------------------------------------------------
Message: 1
Date: Wed, 20 Mar 2013 09:24:12 -0700 (PDT)
From: "J. Forster" <jfor at quikus.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Subject: Re: [time-nuts] WWVB Clocks don't sync anymore (revisited)
Message-ID:
<65101.12.6.201.31.1363796652.squirrel at popaccts.quikus.com>
Content-Type: text/plain;charset=iso-8859-1
Have you tried to put BPSK through a narrow band filter and looked at the
envelope at the output?
-John
==========
> Hi
>
> Also consider that some of these receivers use a narrowband crystal filter
> in front of the IC. I doubt they spend a ton of money on the components,
> so
> that may not be the world's best crystal in terms of aging. If it ages far
> enough the receiver simply goes deaf. If it ages a bit less than that, it
> slices off one sideband much more than the other. That's likely to do all
> sorts of odd things to it's ability to ignore phase modulation.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Herbert Poetzl
> Sent: Wednesday, March 20, 2013 10:58 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] WWVB Clocks don't sync anymore (revisited)
>
> On Wed, Mar 20, 2013 at 02:34:19AM -0400, Bill S wrote:
>
>> Interestingly, I have three timepieces that will no longer
>> synch to wwvb.Two Radio Shack digital clocks and a Casio
>> wristwatch that I've worn for a couple of years and was always
>> pretty much dead on. Like Paul, I have an analog Lacrosse clock
>> that is running correctly. Nothing I've tried will make the
>> other clocks synch.
>
> Maybe this is related to the phase modulation time code
> protocol used by WWVB since October 29th, 2012.
>
> Their website also states that clocks using information
> from the carrier will no longer work, and that during the
> transition period (at least March 21st 2013), the PM
> signal will be turned for for 30 minutes twice a day
> (noon and midnight MST) so maybe check if the clocks
> sync then?
>
> best,
> Herbert
>
> http://www.nist.gov/pml/div688/grp40/wwvb.cfm
>
>> Bill_S W2FMA
>
>> On 3/19/2013 5:29 PM, paul swed wrote:
>>
>>> Funny you bring this up. I am just noticing a sharp clock that
>>> I always use and it has been accurate. But it did not flip
>>> with the time change this time and though it says its locked
>>> its off by 45 seconds slow. Yet a lacross clock across the
>>> room seems to be on second wise but never flipped with the
>>> time change. As I say its just becoming apparent. Regards Paul
>>> WB8TSL
>
>>> On Tue, Mar 19, 2013 at 4:55 PM, Clint Turner
>>> <turner at ussc.com> wrote:
>
>>>> A few weeks ago I posted a question/comment about some of
>>>> my WWVB-based "Atomic" clocks no longer setting themselves
>>>> properly. These two clocks, SkyScan #86716, would show the
>>>> symbol indicating that they had set themselves, but their
>>>> time was drifting away from UTC. Interestingly, they *would*
>>>> set themselves exactly once upon installation of the battery,
>>>> but never again.
>
>>>> Since that time, I've done a bit of digging around.
>
>>>> The first suspicion was that, perhaps, the NIST had fudged a
>>>> bit in the WWVB timecode recently, so I manually decoded a
>>>> few frames and analyzed them: Nothing suspicious there.
>
>>>> The next question was if the addition of the BPSK somehow
>>>> skewed the timing of the TRF's AGC/threshold - but logically,
>>>> this didn't make sense since the clock *did* set itself
>>>> exactly ONCE - and it wouldn't have been able to do this at
>>>> all were this the case. Out of curiosity I poked around on
>>>> the board and found the trace containing the time code and
>>>> found that despite the BPSK, its timing was exactly as it
>>>> should have been: No surprise there.
>
>>>> This left the clock itself, so I did what any other Time Nut
>>>> would do: I built a WWVB simulator.
>
>>>> Initially, I set it to a 2010 date - a time that I knew that
>>>> the clock worked properly. I had two clocks: One that I'd
>>>> just reset by pulling and replacing the battery while the
>>>> other had been "stuck" for a few weeks, not resetting itself
>>>> nightly as it should. I put both of these in the coupling
>>>> loops from my WWVB simulator and over the next few days, the
>>>> recently re-set clock happily synchronized itself while the
>>>> other one with the 2013 date was still "stuck." I then reset
>>>> that clock and it, too, behaved itself from then on.
>
>>>> I then reset the clock on the simulator to a February 2013
>>>> date and time. Initially, both clocks reset themselves to
>>>> the current time and date at their next midnight, but after
>>>> that, they got "stuck", never resetting themselves at "night"
>>>> again.
>
>>>> So, it appears to be a problem with "Broken Sand" (e.g. a
>>>> silicon problem).
>
>>>> For the morbidly curious, I have documented my efforts here:
>
>>>> http://ka7oei.blogspot.com/**2013/02/did-nist-break-bunch-**o
>>>> f-radio.html<http://ka7oei.blogspot.com/2013/02/did-nist-brea
>>>> k-bunch-of-radio.html>- The initial testing
>
>>>> http://ka7oei.blogspot.com/**2013/03/yes-nist-did-break-**
>>>> bunch-of-radio.html<http://ka7oei.blogspot.com/2013/03/yes-ni
>>>> st-did-break-bunch-of-radio.html>- The testing with the WWVB
>>>> simulator
>
>>>> 73,
>
>>>> Clint KA7OEI
>
>>>> ______________________________**_________________
>>>> time-nuts mailing list -- time-nuts at febo.com To
>>>> unsubscribe, go to https://www.febo.com/cgi-bin/**
>>>> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailm
>>>> an/listinfo/time-nuts> and follow the instructions there.
>
>>> _______________________________________________ time-nuts
>>> mailing list -- time-nuts at febo.com To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and
>>> follow the instructions there.
>
>> _______________________________________________ time-nuts
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------------------------------
Message: 2
Date: Wed, 20 Mar 2013 09:03:18 -0700 (PDT)
From: "J. Forster" <jfor at quikus.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Subject: Re: [time-nuts] WWVB Clocks don't sync anymore (revisited)
Message-ID:
<61948.12.6.201.31.1363795398.squirrel at popaccts.quikus.com>
Content-Type: text/plain;charset=iso-8859-1
If a clock uses a narrow (high Q)filter, the BPSK may mess up the
amplitude response. The Time Code is modulated AM on the carrier.
If this is the case, broadening the filter, possibly by adding shunt
resistance, might fix the issue.
FWIW,
-John
============
> On Wed, Mar 20, 2013 at 02:34:19AM -0400, Bill S wrote:
>
>> Interestingly, I have three timepieces that will no longer
>> synch to wwvb.Two Radio Shack digital clocks and a Casio
>> wristwatch that I've worn for a couple of years and was always
>> pretty much dead on. Like Paul, I have an analog Lacrosse clock
>> that is running correctly. Nothing I've tried will make the
>> other clocks synch.
>
> Maybe this is related to the phase modulation time code
> protocol used by WWVB since October 29th, 2012.
>
> Their website also states that clocks using information
> from the carrier will no longer work, and that during the
> transition period (at least March 21st 2013), the PM
> signal will be turned for for 30 minutes twice a day
> (noon and midnight MST) so maybe check if the clocks
> sync then?
>
> best,
> Herbert
>
> http://www.nist.gov/pml/div688/grp40/wwvb.cfm
>
>> Bill_S W2FMA
>
>> On 3/19/2013 5:29 PM, paul swed wrote:
>>
>>> Funny you bring this up. I am just noticing a sharp clock that
>>> I always use and it has been accurate. But it did not flip
>>> with the time change this time and though it says its locked
>>> its off by 45 seconds slow. Yet a lacross clock across the
>>> room seems to be on second wise but never flipped with the
>>> time change. As I say its just becoming apparent. Regards Paul
>>> WB8TSL
>
>>> On Tue, Mar 19, 2013 at 4:55 PM, Clint Turner
>>> <turner at ussc.com> wrote:
>
>>>> A few weeks ago I posted a question/comment about some of
>>>> my WWVB-based "Atomic" clocks no longer setting themselves
>>>> properly. These two clocks, SkyScan #86716, would show the
>>>> symbol indicating that they had set themselves, but their
>>>> time was drifting away from UTC. Interestingly, they *would*
>>>> set themselves exactly once upon installation of the battery,
>>>> but never again.
>
>>>> Since that time, I've done a bit of digging around.
>
>>>> The first suspicion was that, perhaps, the NIST had fudged a
>>>> bit in the WWVB timecode recently, so I manually decoded a
>>>> few frames and analyzed them: Nothing suspicious there.
>
>>>> The next question was if the addition of the BPSK somehow
>>>> skewed the timing of the TRF's AGC/threshold - but logically,
>>>> this didn't make sense since the clock *did* set itself
>>>> exactly ONCE - and it wouldn't have been able to do this at
>>>> all were this the case. Out of curiosity I poked around on
>>>> the board and found the trace containing the time code and
>>>> found that despite the BPSK, its timing was exactly as it
>>>> should have been: No surprise there.
>
>>>> This left the clock itself, so I did what any other Time Nut
>>>> would do: I built a WWVB simulator.
>
>>>> Initially, I set it to a 2010 date - a time that I knew that
>>>> the clock worked properly. I had two clocks: One that I'd
>>>> just reset by pulling and replacing the battery while the
>>>> other had been "stuck" for a few weeks, not resetting itself
>>>> nightly as it should. I put both of these in the coupling
>>>> loops from my WWVB simulator and over the next few days, the
>>>> recently re-set clock happily synchronized itself while the
>>>> other one with the 2013 date was still "stuck." I then reset
>>>> that clock and it, too, behaved itself from then on.
>
>>>> I then reset the clock on the simulator to a February 2013
>>>> date and time. Initially, both clocks reset themselves to
>>>> the current time and date at their next midnight, but after
>>>> that, they got "stuck", never resetting themselves at "night"
>>>> again.
>
>>>> So, it appears to be a problem with "Broken Sand" (e.g. a
>>>> silicon problem).
>
>>>> For the morbidly curious, I have documented my efforts here:
>
>>>> http://ka7oei.blogspot.com/**2013/02/did-nist-break-bunch-**o
>>>> f-radio.html<http://ka7oei.blogspot.com/2013/02/did-nist-brea
>>>> k-bunch-of-radio.html>- The initial testing
>
>>>> http://ka7oei.blogspot.com/**2013/03/yes-nist-did-break-**
>>>> bunch-of-radio.html<http://ka7oei.blogspot.com/2013/03/yes-ni
>>>> st-did-break-bunch-of-radio.html>- The testing with the WWVB
>>>> simulator
>
>>>> 73,
>
>>>> Clint KA7OEI
>
>>>> ______________________________**_________________
>>>> time-nuts mailing list -- time-nuts at febo.com To
>>>> unsubscribe, go to https://www.febo.com/cgi-bin/**
>>>> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailm
>>>> an/listinfo/time-nuts> and follow the instructions there.
>
>>> _______________________________________________ time-nuts
>>> mailing list -- time-nuts at febo.com To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and
>>> follow the instructions there.
>
>> _______________________________________________ time-nuts
>> mailing list -- time-nuts at febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and
>> follow the instructions there.
> _______________________________________________
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>
------------------------------
Message: 3
Date: Wed, 20 Mar 2013 18:02:56 +0100
From: "Dr. G?tz Romahn" <goetz at g-romahn.de>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] Repair of PRS10 Lamp Assembly
Message-ID: <5149EBC0.90109 at g-romahn.de>
Content-Type: text/plain; charset=windows-1252; format=flowed
Thanks for all your comments so far. I did sniffing with a cable loop
located in the lamp cell (thank you Bob for this advice), and surprise
(!) RF power does not degrade with time but does stay rock solid after
ignition. So, sorry Bob, you did not win the bet this time. Next step
should be to check, what is going on with heating. Not so easy since all
the many diagnostics are within range. As a provisory measure I decided
to cheat the lamp heat regulator somehow by paralleling a 39 KOhm
resistor to R226 an thereby shifting the operating point of the
thermistors in lamp assembly. PPR10, when started properly, now seems to
work as expected.
One comment to the lamp starting algorithm: oscillator FET drain and
gate voltage are controlled via factory set values but not on an
individual basis. All lamps are started with FET voltage set to maximum
available via SD2=255 and after inginition to some reduced value also
via SD2=55. So there is no need to change set values for different lamp
assemblies.
Goetz
Am 18.03.2013 01:34, :
> Hi
>
> I'd bet that something is keeping the oscillator from putting out enough RF.
The circuit is simple enough that the issue is one of a very small number of
parts. I'd bet on the FET?..
>
> Bob
>
> On Mar 17, 2013, at 8:24 PM, Brucekareen at aol.com wrote:
>
>> I am afraid the PRS-10 lamp starting algorithm is a little involved. I
>> believe that once the lamp temperature is in the starting range, the
>> microprocessor ramps up the drain and possibly gate voltage of the heating
>> oscillator FET until the bulb strikes as evidenced by a DC signal at the
detector.
>> If the lamp overheats (as measured by thermistors imbedded in the back of
>> the lamp block), at some point the microprocessor will reduce the drain
>> voltage to a safe steady-state value.
>>
>> The starting constants for each individual PRS-10 are factory-set in the
>> unit's programmed software, and as far as I know, access to change these
>> settings has not been made available yet to end users. This makes it
>> difficult to swap lamps between units.
>>
>> I have a PRS-10 with a lamp that is just on the edge of starting properly.
>> Since I cannot change the factory-programmed values, I have tried adding
>> a shunt resistor to increase the lamp current to the point where it would
>> reliably start. But, unfortunately, other problems seem to be keeping the
>> unit from working properly.
>>
>> The only luck I have had in repairing a non-working PRS-10 with certainty,
>> was one in a Symmetricom 2500 Time Source that turned out to have a failed
>> Mini-Circuits VCO on the synthesizer board. Replacing the VCO module
>> restored proper operation.
>>
>> Perhaps someday the factory will provide end users with access to what are
>> now "factory-only" settings.
>>
>> Bruce, KG6OJI
>> _______________________________________________
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------------------------------
Message: 4
Date: Wed, 20 Mar 2013 11:22:51 -0600
From: Clint Turner <turner at ussc.com>
To: time-nuts at febo.com
Subject: Re: [time-nuts] WWVB Clocks don't sync anymore (revisited)
Message-ID: <5149F06B.4040209 at ussc.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I found a note on the SkyScan web site itself that attempts to offer an
explanation/excuse as to why some of their clocks no longer synchronize:
http://skyscanatomicclocks.com/site/help-my-86715-86730-87315-is-not-catching-the-signal/
This, however, is a BIG red herring.
The ONLY change that was made of any significance was the addition of a
BPSK component to the carrier. Fortunately, this occurs at the instant
that the UTC second begins - when the carrier drops in amplitude -
which, in the unlikely event that the "ringing" of the filtering in
these clocks TRF receivers were enough be at all sensitive to BPSK, this
phase shift would only go toward assisting them in their immediate
detection of the amplitude reduction of the ASK signal transmitted by
WWVB. Certainly, by the minimum time at which the carrier amplitude
might increase (0.2 seconds for sending a binary "0") the filter has
pretty much recovered from the effects of the phase reversal. In
programming the WWVB simulation, I also found that the clock's timing
was very forgiving - seeming not to care if the timing of these bits was
over 100ms out of spec in either direction! (The fact that the clock
reliably locked once, after replacing the battery, indicated that it had
no trouble with the "different" modulation.)
On these clocks I was able to locate the circuit board trace that
connects one epoxy-covered blob (the TRF chip) to the other (the clock
itself) and find the demoduated time code which was present after a
power-cycle. Even with a fairly poor S/N and the added BPSK, the
bandwidth of the TRF is wide enough that time code very nicely matched
what WWVB was sending - albeit that it was offset very slightly in time
(group delay, etc.) This was easily determined with a dual-trace scope
with one channel coming from a strong audio beat note from an LF
receiver on a good antenna, and the other channel looking at this logic
line.
As far as any of these consumer-grade clocks are concerned, there is no
modulation present other than the ASK signal and I tend to believe the
assertion by the NIST that the addition of the BPSK would be transparent
to these receivers.
While I don't have an answer for those clocks that flat out refuse to
acquire a time signal in the first place (again, even my clocks would
lock exactly once after replacing the battery) it would seem clear that
these particular units have a problem with their programming in that
they don't know what to do with the now-current dates. I've been
experimenting on the WWVB simulator with different years to try to more
accurately determine the window during which they work, but the initial
indications are that the period for which the programming works ranges
from somewhere in the late '90s to mid-late '12.
As I note on the web page, the 60 kHz WWVB frequency is, unfortunately,
fairly close to that on which many switching converters operate - or
near its 2nd harmonic and I've found that having an operating CFL or
switching "wall wart" in somewhat close proximity can prevent one of
these clocks from acquiring lock - and this is in an area in which the
signal's field strength is quite strong, somewhere in the 5
millivolts/meter range! In at least one occasion, I've found that a
non-locking clock could be explained by the recent addition of one of
these unintentional radiators.
73,
Clint
KA7OEI
------------------------------
Message: 5
Date: Wed, 20 Mar 2013 18:28:42 +0100
From: Herbert Poetzl <herbert at 13thfloor.at>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] Is possible precise 1pps?
Message-ID: <20130320172842.GO27691 at MAIL.13thfloor.at>
Content-Type: text/plain; charset=us-ascii
On Wed, Mar 20, 2013 at 01:48:59PM +0100, Attila Kinali wrote:
> On Mon, 18 Mar 2013 09:21:57 +0100
> "Pieter ten Pierick" <time-nuts-mail at tenpierick.com> wrote:
>>> The -T models are not that expensive. The problem is that you
>>> have to buy them in batches >30 to get down to a reasonable
>>> price. U-blox seems to have taken the stance, that small
>>> buyers are not really benefitial to their business (which is
>>> understandable when you can sell millions of pieces on the
>>> chinese market). But they nevertheless support these small
>>> buyers trough their webshop where you can buy single pieces
>>> (which is far better than most manufacturers who do not sell
>>> single pieces at all).
>> Sounds like a time-nuts group buy?
> Tried that a year or two ago. Did even get a "special" price
> from u-blox that would usually need higher volumes, but it
> didn't take off.
> Attila Kinali
May I ask, what the "special" price was, just to get the
right perspective here?
Thanks in advance,
Herbert
> --
> The trouble with you, Shev, is you don't say anything until you've saved
> up a whole truckload of damned heavy brick arguments and then you dump
> them all out and never look at the bleeding body mangled beneath the heap
> -- Tirin, The Dispossessed, U. Le Guin
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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