radio time code clock error

Nope. My clocks are just fine. Sometimes my WWVB based clocks go nuts from RF noise in the shop. They then reset themselves after midnight, when 60 KHz propagation is best. In the UK, you're probably using MSF. They do have some scheduled outages, but that's not the problem this time: Offhand, I would guess(tm) that your unspecified model radio clock has a dying battery. My various clocks do some rather strange things when the battery is low.

You might want to fasten your seat belt on June 30th. The good news is that you'll get an extra second of sleep during the night of June 30th.

More:

At the tone, the time will be: Ummm... never mind.

Not specified as litterally no name/model on it. Casio watch, I compared it to , was fine . At least I now know not to rely on "no-name" and use it in alarm mode with another alarm clock. If it went erroneous "to the west" it would not be so problematic

As the minuits agree, but the hours are off, I would look for a setting as to which time zone the clock is set for.

I've never seen an option to change country of use, or any legend like LON for London as in the Casio. Automatically seems to selct UK , the strongest signal? along with automatic daylight saving changes. Just pressed reset to remind me that no country option comes up and within 10 minutes had sync'd with the Casio , in effect. Tried Google Images but this one not seen in the first 3 pages of pics of silver desktop "radio controlled" LCD clocks

So perhaps that was the failure mechanism. Rugby went down for maintainence or its signal got locally shadowed/echoed/interferred with and if Darmstadt was a stronger/clearer? signal , perhaps reset itself to CET time for a while. The Casio having a preset station option , it may loose updating but it would not try to find another code source.

Ah, CET is in advance of GMT (BST - 1 ) not behind, and I doubt there is a transmitter for the Cape Verde Islands.

I have an Oregon Scientific alarm clock that has five prominent buttons on its face: Clock, UP, DOWN, ALARM, ZONE.

I have hit the zone button by mistake before. It steps through the 4 US time zones.

I live in a fringe reception area for the german time signal at 77.5kHz and have many clocks that use this signal but because a marginal reception the y do not always sync. The curious thing about this is every night I have a different set of clocks sync, they seem to decide at random when the signal was good enough.

The oldest one is 13 years old and is an alarm clock I check daily, in thes e years I have had it three times take an incorrect time/date probably from interference. It either takes the right time or does not sync, three times in 13 years seems not bad for the simple parity bit protection the protoco l uses.

I think, however, it is somewhat dangerous to have the clocks sync at night *after* you have checked they are set correctly, so if bad reception sets wrong data they will fail to wake you up at the right time.

Jeroni Paul wrote: "The oldest one is 13 years old and is an alarm clock I check daily, in these years I have had it three times take an incorrect time/date probably from interference. It either takes the right time or does not sync, three times in 13 years seems not bad for the simple parity bit protection the protocol uses.

I think, however, it is somewhat dangerous to have the clocks sync at night *after* you have checked they are set correctly, so if bad reception sets wrong data they will fail to wake you up at the right time. "

Enough reasons for me not to use the freakin' things...

I've got the best time sync source of all, courtesy the NIST and WWVB! ;)

Spain? According the coverage map at: Yes, the signal is probably not very strong and you're in the skywave only region.

That sounds like the older amplitude modulated system. DCF77 also transmits a phase modulated signal, which works better for weak signal due to better processing gain. I'm in the USA and have not tried it with over-the-air DCF77, but have played with simulators and with WWVB, which also has a phase modulated BPSK signal. The problem is that the technology seems to be patented and chips are not forthcoming. Also, the addition of BPSK modulation caused some old WWVB receiver chips to fail. No clue what the situation was with DCF77 but it might be worth checking.

Kinda sounds like you're getting some local interference. It doesn't take much computah or switcher noise to trash the signal, especially when it's weak in the first place. If your devices have a loopstick for an antenna, they are directional, with the strongest signal perpendicular to the loopstick. I was having random updates until I moved my WWVB clock away from several switching power supplies.

It's a bit more than just the parity bit. Some chips require that the correct time be received successfully more than once before it will sync. This is a function of the chip design.

Sorry, but you don't have a choice as to what time to sync. Propagation at VLF frequencies works best after midnight in the USA. I think it's the same for a north-south path, but I'm not sure. Note the increases in coverage area after midnight for WWVB: I couldn't find something similar for DCF77.

I thought low frequencies were used by WWVB (and WWVL before it) because it was all ground-wave, and well penetrating.

If it was on shortwave, you would be stuck with a given frequency for a givne time, which of course is why WWV transmits on a bunch of frequencies.

The reason I've seen for late night sync'ing (and which makes sense) is that in the wee hours of the morning, fewer people are up, thus much less manmade interference. So the CFLs are turned off, the tv sets are turned off (probably a bigger issue when they were actually CRTs, all that horizontal sync frequencies into the deflection coil), lots of other things that might be on in the daytime are off so they aren't making as much noise.

I've noticed this. My Casio Waveceptor watch starts looking at midnight local time, and if I have the CFL on at the time, it likely doesn't sync up, but will at a later hour (the watch is better than most of the clocks, since it tries multiple times). COnversely, if I have the CFL off, it generally will sync at midnight.

And I'm probably at the far edge of the reliable reception area.

Of course, with at least some of the clocks, one does have the option of pressing button (or putting the batteries back in) so the clock tries to sync up, no matter what time it is.

Michael

Have you had the situation of the displayed time jumping by an hour or two? As an alarm clock, losing synch and drifting a second or two , to a background quartz crystal clock, is no great problem

The skywave doesn't magically go away at lower frequencies. For example, here's a study on hearing both WWVB and JJY (Japan) in Germany, which certainly would require skywave propagation. See 3rd graph from the top. Unfortunately, I've never bothered to do any DXing on VLF, but have been told that it's possible to hear Europe and Japan in California if the conditions are right. VLF DX list:

Unlike HF (high freq) propagation, which is "bent" by the ionosphere back towards the ground, VLF frequencies are reflected off the D layer.

Actually, VLF has the same problem. Beyond some distance (which varies with antenna size and power level), the various time sync stations become very sensitive to ionospheric layer conditions, which is mostly controlled by the sun. During the day, skywave propagation sucks, while ground wave is unaffected. However, when there's dark over most of the distance between the transmitter and the receiver, the skywave returns. More on how it works:

That would be so nice if it were true, but it's not. It's not man made interference that causes most reception problems, it's lightning and atmospheric RF noise that are extremely high at VLF frequencies. See the graph at: At 60 KHz, the noise level is about 80dB above the normal thermal noise. When designing a receiver for 60 KHz, the problem is not the usual NF (noise figure) and gain, but rather being able to remain linear and handle the overload produced by the noise. That's why you often see VLF receiver front ends with heat sinks on the RF transistors.

Incidentally, the high noise levels is also why you can get away with using tiny antennas with loss instead of gain. A bigger antenna will amplify the noise and the signal equally which doesn't improve things. A bigger antenna also produces more voltage at the receiver input, which has to handled by an increasingly higher voltage and power input stage. However, what a bigger antenna might do is increase the Q of the antenna (i.e. decrease the antenna bandwidth) which would pickup less off frequency noise, which will help increase the SNR (signal to noise ratio).

Look again at the noise graph, and notice the red line added showing man made noises. At 60 KHz, the man made noise is about equal to the atmospheric noise.

If you want to pursue such a noise source survey, I suggest you build a loop resonant at 60 KHz and plug into an oscilloscope looking for noise. I suggest a very high Q magnetic loop so that it only picks up noise very close to 60 KHz. Just about anything with a switching power supply should show up as a noise source. I have some opinions on CFL lamps, LED lamps, and plasma TVs which I'm not quite sure are correct, so I'll not comment on those. Let's just say I have some very quiet LED lamps and some VERY noisy LED lamps.

That sounds about right. The chip, usually made by C-Max uses an algorithm to determine when to listen. The problem is battery life. It makes no sense to listen during daylight hours, so it doesn't. If it sync at midnight, it doesn't try again later. If it fails, it retries according to some pattern. I used to have the link to the details, but can't find it right now. This is close but not the one I was looking for:

Probably true with a wristwatch receiver or consumer device. Not true with a proper loop antenna, which gets much better range. In the early 1980's, I setup a WWVB receiver in an area infested with high electrical noise. None of the commodity WWVB clocks would work. A shielded loop antenna and overkill coax shielding did the trick. Something like this, except my loop was circular and about 1 meter wide:

I hacked one of clocks to do that so I could make measurements: The receiver inside the antenna has an "enable" line to turn it on and off. In this device, it's labeled PON. The clock/display/control chip enables it according to the previously mentioned algorithm. I tied the line high (after disconnecting it from the clock) so that it would run continuously. It takes about 3 weeks to kill the two AAA batteries when running continuously.

Clean signal that will decode correctly: Noisy signal that won't work:

Second best. They adjust those ones to match that yellow thing up in the sky. ;)

Cheers

Phil Hobbs

(We just had a leap second.)

Good observer, yes, Spain. Also the Pyrenees are in the way blocking most g round signal.

I knew about the phase modulated encoding on the signal but I am not sure i f any of my clocks use that. The older ones sure do not, time ago I dissass embled the oldest alarm clock and scoped the signal output from its radio b oard and I could see the 0.1/0.2 sec signal drop.

There is a long wave radio transmitter in France at 162 kHz that carries ti me information by phase modulation of its carrier:

Yet, if I had one clock next to a noise source I would expect it to sync le ss times than the rest. But no, there appears to be a random distribution.

That's what I belived, but then how did it receive incorrect data? Did it a ctually receive the same wrong data twice in a row? The algorithm could als o check for a reasonable deviation against the current setting.

Maybe a setting to enable sync only during weekends or only when the alarm function is disabled.

I think on one occasion it was several hours off. You could tell it was a wrong bit value as the data would be wrong by a multiple of two.

I haven't looked into the situation for about a year. I also don't know the situation in Europe. To the best of my limited knowledge, there are no commodity clocks and no commodity chips being made that use phase modulation, in the USA. The technology appears to be owned by Everset, which has done absolutely nothing for several years. I could find no distributor that carries their chips. My previous requests for samples, pricing, and delivery were ignored: If you find a consumer grade WWVB chip or receiver that do BPSK, I would be interested.

I'm not sure, but might be able to take the demodulated output of a

You can probably get better info from the Time-Nuts mailing list:

Nope. WWVB sends the time code at the rate of 1 bit/second (1 baud). One frame is 60 seconds. Hopefully, the European systems are similar. All it takes is one noise hit every 60 seconds, and you'll receive nothing. If your local noise source is intermittent or random, then it's more a matter of timing and bad luck that will determine if the clock decodes anything useful.

Good question. I don't know. The only time I've seen an incorrect display was when I was building a WWVB emulator and spraying garbage data everywhere: However, I've never seen a random erroneous date or time.

Very unlikely that it might receive the same garbage successfully twice in a row but possible. However, note that the redundancy requirement is totally in the chip uses, which might vary in programming and capabilities.

I don't think so. Once it gets a valid time to display, it turns off the receiver to save battery power. No need to decode more than one or maybe two frames.

Personally, I want a graph of signal strength and SNR over a few days period. Whether anyone is willing to pay for such a feature is debatable.

Does the NIST use a sundial for a primary time standard? I realize that budget cuts have necessitated economy measures, this seems a bit extreme.

Yep. That felt good. I got one second of extra sleep.

In a way, they do. Civil time is adjusted to match mean solar time.

I was awake, advancing science. ;)

Cheers

Phil Hobbs