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Methods for improving 60kHz RF signal (WWVB)?

Started by Frnak McKenney March 13, 2014
Hi, Jeff.

Thanks for joining in.

On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:
> On Thu, 13 Mar 2014 09:51:15 -0500, Frnak McKenney ><frnak@far.from.the.madding.crowd.com> wrote: > >>I have two "atomic clocks": one is a La Crosse LCD unit, the other >>an "analog" wall clock whose hands are driven by a WWVB-sync >>1xAA-powered mechanism. Following the recent "let's screw with >>everybody's clocks" cycle neither of my "atomic clocks" caught it, >>and I was reminded that I was Going To Fix This Problem last time. >>And the time before... <grin!> > > That was in late 2012 that WWVB added phase modulation and broke many > WWVB receivers. If that's your problem, there are a few fixes, but I > suspect they're only useful for higher end receivers. ><http://www.maxmcarter.com/rubidium/2012_mod/>
Good thought. Unfortunately, I've had WWV/WWVB reception problems as long as I've lived here. I finally build a 1m dia tuned loop so my Heath Most Accurate Clock could reliably receive WWV 10MHz. That doesn't mean that the 2012 change didn't make things worse, it just means that it's hard for me to distinguish "a pain to reset before 2012" from "a slightly bigger pain to reset after 2012". <grin!>
>>After some years I've discovered that, if I place my clocks near the >>west-most window and leave them for a few days, they will usually >>re-sync with the current WWVB time; if I don't do this it may be >>weeks or months before they pick up a strong enough signal to reset. > > Sounds like interference. I have the same problem at both my house > and my office. I have about 6 assorted WWVB receivers, all of which > do not like being near any switching power supply, CCFL lamp, some > LED lamps, solar inverters, etc. I built a 60KHz sniffer out of a > loopstick cannibalized from one of my cheap receivers that didn't > make it through the 2012 transition. I got lazy and just attached > it to portable oscilloscope and retuned it to 60KHz to compensate > for the scope probe capacitance. Wandering around the house, I > identified some of the major noise source. I later did the same > test with a larger 60 KHz loop antenna.
Good thought. As in, "make sure you're solving the right problem".
> ... Don't try this with a > shielded loop as I was looking for the magnetic component of the > signal, not the electric.
I must be misreading this. I was under the impression that a shielded loop was preferred for WWVB-ish signal detection because it _was_ less sensitive to E-field noise. Or am I missing something subtle here?
>>Is there some simple way of strengthening the WWVB signal so my >>clocks will reset themselves automatically, preferably one that >>doesn't involve stringing wires to each device? > > The article provided by Neon John: ><http://www.ka7oei.com/wwvb_antenna.html> > is the best I've seen. However, methinks some explanation of what's > happening might be useful. You probably have noticed that 60 KHz > antennas come in various sizes. There are tiny solenoid wound > loopsticks that fit inside wristwatches. There are typically 8-10mm > diameter ferrite rods and coils in various lengths. There are large > unshielded loops and there are large shielded loops.
My analog clock has a WWVB-sync'ed movement like this one: http://www.amazon.com/Atomic-Clock-Movement-Shaft-Length/dp/B007KA54RW/ and there isn't room inside it for much of an antenna. One might guess that the LaCrosse WS-8418 has a slightly larger antenna, but it would be a guess; I haven't had an excuse to take it apart (yet).
> ... However, if you > test these devices in an area free from EMI interference, you'll > probably find that they all have approximately the same field > strength sensitivity when operating a given receiver. I've only > compared a large home-made loop with a ferrite loopstick rod > antenna, and they were (as far as I could tell) the same. > > So, what's the difference? Well, the unloaded Q of the various > antennas are different. My guess(tm) is about: > wristwatch antenna 50 > loopstick rod 100 > shielded loop 200
> Loaded Q is less, and often as low as 1/2 of the unloaded Q. In > this case, the Q determines how much extraneous noise the receiver > has to deal with. Higher Q picks up less noise, is generally > better, but can have a problem with temperature drift. Use only the > best capacitors. Too much Q is also a problem if you want to > receive other time stations without retuning the antenna. Somewhere > between 50 and 100 seems about right.
><http://www.c-max-time.com/tech/antenna.php>
Thank you for the pointer. I've filed it for future reference. ( Do the Aerial Connection diagrams a-d look mislabeled to you? )
><http://www.tinaja.com/glib/WWVBexps.pdf> > > Most better receivers use shielded loops. However, the noise > reduction is not just from the increased Q of the loop. It's also > because such large loops are usually mounted outside, away from the > switching power supplies. They're also magnetically shielded and > thus are immune to direct (transformer) coupling from inductors and > xformers. > > In short, if you want to get rid of the interference problem, get a > better antenna and/or move the antenna away from the interference > sources. > > As you note, propagation varies with the time of day. In general, > the best signals are when both the transmitter and receiver are at > night.
Agreed. I don't forsee ever needing instant mid-day updates, though.
><http://tf.nist.gov/tf-cgi/wwvbmonitor_e.cgi> ><http://www.nist.gov/pml/div688/grp40/vb-coverage.cfm>
> (A working Java is required). What the graphs mean is that it's not > going to update at some times of the day, no matter how good a > location or hardware you are using. Interestingly, you'll find that > 60 KHz propagation does not exhibit short term fades and dropouts > that are so common on the higher shortwave frequencies with WWV.
If I can improve things to the point where it gets updated every night I'll be more than happy. <grin!>
>>And, if I have to build it, what would be a good unidirectional LF >>antenna type? > > Bidirectional is usually good enough. Loop yagi style constructs > are impractical because the element spacing will need to be about > 1/4 wavelength apart, which at 60 KHz is about 1,250 meters. Some > kind of phasing contraption using two loops and null out a single > direction if you're dealing with a difficult noise source, such as > an arcing power line insulator also won't work. Getting the loops > far enough apart might be difficult. Too close, and they hear the > same signals and cancel everything. > >>I have two neighbors to my SW and NW, and I really don't >>want to mess up their equipment. <grin!> > > Build a 60 KHz sniffer and see if they really are a problem. My bet > is that if you have interference problems, it's local.
Good suggestion, but I think I was trying to say that I didn't want any signal amplifier I built to cause problems for my neighbors.
> Incidentally, there's a small chance you'll run into something like > these solar micro-inverters: ><http://www.solarvoltpower.net/resources/KD-WVC-260W%20Owners%20Manual.pdf> > They switch at 50 KHz, but communicate low speed data to a computah > with a 60 KHz carrier. I haven't seen one yet, but I'm told that they > do cause WWVB problems.
Well, if I build a 60Hz "sniffer" I should be able to find one if I have it. Thank you for the suggestions. Frank -- Generations of students in the social sciences have been exposed to entertaining lectures that point out how dumb everyone else is, constantly wandering off the path of logic and getting lost in the fog of intuition. Yet logical norms are blind to content and culture, ignoring evolved capacities and environmental structure. Often what looks like a reasoning error from a purely logical perspective turns out to be a highly intelligent social judgment in the real world. Good intuitions must go beyond the information given, and therefore, beyond logic. -- Gerd Gigerenzer / Gut Feelings: The Intelligence of the Unconscious. -- Frank McKenney, McKenney Associates Richmond, Virginia / (804) 320-4887 Munged E-mail: frank uscore mckenney aatt mindspring ddoott com
On 15/03/14 18.45, Jeff Liebermann wrote:
...
> That was in late 2012 that WWVB added phase modulation and broke many > WWVB receivers. If that's your problem, there are a few fixes, but I > suspect they're only useful for higher end receivers. > <http://www.maxmcarter.com/rubidium/2012_mod/>
... Do any of you know if this IC (CME8000) works with the new WWVB?: CME8000 Datasheet: http://www.c-max-time.com/downloads/getFile.php?id=533 Quote: "... 9 Protocol recognition To get a fast information of the received protocol, after every power on the received signal will be compared with the chosen protocol. The bit stream is checked for pulses with characteristically pulse duration. To start a new protocol recognition it is necessary to reset via PON. ... WWVB is designed such that when S1, S2 selected WWVB, CME8000 scans automatically in parallel the 3 possibilities in JJY, WWVB and MSF. Once protocol identified is not WWVB, user should switch to its correct protocol setting and confirm once again on the correct setting in 60kHz. ... WWVB Signal: at minimum 1&mu;V input voltage all 60 bit of the signal are decoded without failure and the frame marker and the position markers (800ms) are recognized also. A pulse of ~500ms is recognized as a binary 1 and a pulse of ~200ms is recognized as a binary 0. After reception of a complete string, including the frame marker, all bit are stored in the equivalent place in the shift register (bit 1 in cell1, bit 60 in cell 60). ..." CME8000 (ca. 2007 design): http://www.c-max-time.com/products/showProduct.php?id=1 Downloads: http://www.c-max-time.com/downloads/search.php?search=CME8000 /Glenn
Digikey has complete modules:
561-1005-ND

/Glenn
On Sat, 15 Mar 2014 15:05:27 -0500, Frnak McKenney
<frnak@far.from.the.madding.crowd.com> wrote:

>Good thought. Unfortunately, I've had WWV/WWVB reception problems as >long as I've lived here.
Find a spectrum analyzer and look at what you're actually receiving from the antenna. I spent a day troubleshooting a WWVB receiver before I discovered that I had an oscillating RF amplifier in the remote antenna section.
>I finally build a 1m dia tuned loop so my >Heath Most Accurate Clock could reliably receive WWV 10MHz.
Nice. I have a GC-1000 Most Accurate Clock that I'm slowly rebuilding. The original builder was seriously lacking in mechanical ability and made a nice mess.
>Good thought. As in, "make sure you're solving the right problem".
Yep. In general, if you have at least 10dB SNR, you should be able to demodulate WWVB. If you look at the plots at: <http://www.febo.com/time-freq/wwvb/sig-strength/wwvb-spectracom.html> The >10dB SNR is typically about 20 hrs per day. Avoid working around sunset and you'll probably be ok. Most people spend their time trying to maximize the antenna gain. Bad idea as that increases both the signal and the noise equally. What's needed is a way to improve the SNR by reducing the noise pickup. That's the real problem.
>> ... Don't try this with a >> shielded loop as I was looking for the magnetic component of the >> signal, not the electric. > >I must be misreading this. I was under the impression that a shielded >loop was preferred for WWVB-ish signal detection because it _was_ less >sensitive to E-field noise. Or am I missing something subtle here?
Oops. I was writing from memory and got it backwards. It's a magnetic loop and the Faraday shield removes the electric field.
>My analog clock has a WWVB-sync'ed movement like this one: > http://www.amazon.com/Atomic-Clock-Movement-Shaft-Length/dp/B007KA54RW/ > >and there isn't room inside it for much of an antenna. One might >guess that the LaCrosse WS-8418 has a slightly larger antenna, but it >would be a guess; I haven't had an excuse to take it apart (yet).
Well, it's probably larger than the tiny loopstick used in the wrist watches. Here's a possible dissection of a similar clock movement: <http://www.amug.org/~jthomas/wwvbmod.html> Looks like a reasonable size ferrite rod and coil winding. No shielding, which is typical.
>><http://www.c-max-time.com/tech/antenna.php> > >Thank you for the pointer. I've filed it for future reference. ( Do >the Aerial Connection diagrams a-d look mislabeled to you? )
You have good eyes. They should be labeled: a) single ended b) single ended something strange c) balanced center d) balanced center tap coil tap resistors You'll find plenty of errors on the web pile including document downloads with no file extension. Just add .PDF to the filename.
>Agreed. I don't forsee ever needing instant mid-day updates, though.
To save battery power, most such clocks play dead during the day and only wake up when a strong signal might be expected. Typical for the chip is only a few updates per night with a 1 to 24 hr delay after each successful update. If battery operated, they do NOT listen continuously. This is all settable in the chip at the whim of the designer. See the flow chart at: <http://www.c-max-time.com/tech/software6005.php>
>If I can improve things to the point where it gets updated every night >I'll be more than happy. <grin!>
Eliminate interference sources and you should be ok. However, I would have some doubts about the clock module. It seems like might be one that didn't quite survive the WWVB addition of PM in Nov 2012. Find a known working WWVB clock, and position it in the same general area as your clock. If it works, then there may be a problem with the module. More on PM problems: <http://ka7oei.blogspot.com/2013/03/yes-nist-did-break-bunch-of-radio.html>
>> Build a 60 KHz sniffer and see if they really are a problem. My bet >> is that if you have interference problems, it's local. > >Good suggestion, but I think I was trying to say that I didn't want >any signal amplifier I built to cause problems for my neighbors.
Unless it decides to oscillate and become a transmitter, I wouldn't expect any problems. However, hanging a large loop antenna on the fence line might produce some paranoia on the part of the neighbors. I suggest threading some vines through it as natural camouflage.
>Well, if I build a 60Hz "sniffer" I should be able to find one if I >have it.
Ummm... that's 60 KHz, not Hz. It's difficult to tell what you're looking at with a scope. A portable spectrum analyzer would be better, if you can find something that works at 60 Khz. A high end 192 KHz sound cards should work. Probably already been done.... yep: <http://www.geocities.jp/bitalemon3000/english.html> <https://www.youtube.com/user/pobox22cpo> <http://www.qsl.net/dl4yhf/spectra1.html> More on VLF reception using Spectrum Lab software: <http://abelian.org/vlfrx/> Note the graphs with the noise plot. 60 KHz looks ugly and note the comments on buzz from the 12 KV lines. Good luck. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On 15/03/2014 02:59, Jasen Betts wrote:
> On 2014-03-14, Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote: > >>> I used a multi-turn 8" loop antenna encased in 1/2" copper pipe >>> (with a fiber joint to avoid a shorted turn. >> >> Square/rectangular, yes? Or is there some easy way to bend Cu pipe >> into a nice, pretty circle? <grin!> > > anneal it first. (get it red-hot with a propane torch) > then when it cools it'll be soft and can be formed by hand.
ISTR You have to drop it in a bucket of water whilst red hot to make copper stay soft (and avoid the jet of steam and boiling water). -- Regards, Martin Brown
On Sat, 15 Mar 2014 11:04:22 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> >wrote: >>That was in late 2012 that WWVB added phase modulation and broke many >>WWVB receivers. If that's your problem, there are a few fixes, but I >>suspect they're only useful for higher end receivers. >><http://www.maxmcarter.com/rubidium/2012_mod/>
>Aha! I didn't know about that phase modulation addition. Reading >here.... > <http://www.nist.gov/pml/div688/grp40/wwvb.cfm> >the way they did it will raise havoc with the synchronous AGC AM >detection schemes used in most old clocks, and in my old chip >design... > <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> >I'll have to muse over that and see if there's a solution. > ...Jim Thompson
The addition of PM should NOT have broken a synchronous demodulator. At worst, it should re-synchronize within one or two cycles. The shortest WWVB pulse is 200 msec wide or about 12,000 cycles of 60 KHz carrier, which is plenty of time. I don't think your ancient chip has a problem. <http://ka7oei.blogspot.com/2013/02/did-nist-break-bunch-of-radio.html> <http://ka7oei.blogspot.com/2013/03/yes-nist-did-break-bunch-of-radio.html> "Again, the ACTUAL problem with these clocks is that there appears to be a bug in their own firmware/hardware that causes them to lose the ability to re-synchronize themselves on their own, a problem that appears to have manifested itself some time in mid/late 2012." Also: WWVB Clocks don't sync anymore (revisited) <http://www.febo.com/pipermail/time-nuts/2013-March/075111.html> I think you'll find the problem unique to a few specific products: <https://sites.google.com/site/skyscan86715sync/home> -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sat, 15 Mar 2014 15:07:14 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Sat, 15 Mar 2014 11:04:22 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> >>wrote: >>>That was in late 2012 that WWVB added phase modulation and broke many >>>WWVB receivers. If that's your problem, there are a few fixes, but I >>>suspect they're only useful for higher end receivers. >>><http://www.maxmcarter.com/rubidium/2012_mod/> > >>Aha! I didn't know about that phase modulation addition. Reading >>here.... >> <http://www.nist.gov/pml/div688/grp40/wwvb.cfm> >>the way they did it will raise havoc with the synchronous AGC AM >>detection schemes used in most old clocks, and in my old chip >>design... >> <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> >>I'll have to muse over that and see if there's a solution. >> ...Jim Thompson > >The addition of PM should NOT have broken a synchronous demodulator. >At worst, it should re-synchronize within one or two cycles. The >shortest WWVB pulse is 200 msec wide or about 12,000 cycles of 60 KHz >carrier, which is plenty of time. I don't think your ancient chip has >a problem. > ><http://ka7oei.blogspot.com/2013/02/did-nist-break-bunch-of-radio.html> ><http://ka7oei.blogspot.com/2013/03/yes-nist-did-break-bunch-of-radio.html> > "Again, the ACTUAL problem with these clocks is that there appears > to be a bug in their own firmware/hardware that causes them to lose > the ability to re-synchronize themselves on their own, a problem > that appears to have manifested itself some time in mid/late 2012." > >Also: >WWVB Clocks don't sync anymore (revisited) ><http://www.febo.com/pipermail/time-nuts/2013-March/075111.html> > >I think you'll find the problem unique to a few specific products: ><https://sites.google.com/site/skyscan86715sync/home>
I'll run a test signal thru my circuit and see... might play just fine or it may barf ;-) It _is_ a PLL using an XOR (multiply) type of phase detector. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 3/15/2014 2:04 PM, Jim Thompson wrote:
> On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> > wrote: > >> On Thu, 13 Mar 2014 09:51:15 -0500, Frnak McKenney >> <frnak@far.from.the.madding.crowd.com> wrote: >> >>> I have two "atomic clocks": one is a La Crosse LCD unit, the other an >>> "analog" wall clock whose hands are driven by a WWVB-sync 1xAA-powered >>> mechanism. Following the recent "let's screw with everybody's clocks" >>> cycle neither of my "atomic clocks" caught it, and I was reminded that >>> I was Going To Fix This Problem last time. And the time before... >>> <grin!> >> >> That was in late 2012 that WWVB added phase modulation and broke many >> WWVB receivers. If that's your problem, there are a few fixes, but I >> suspect they're only useful for higher end receivers. >> <http://www.maxmcarter.com/rubidium/2012_mod/> >> > [snip] > > Aha! I didn't know about that phase modulation addition. Reading > here.... > > <http://www.nist.gov/pml/div688/grp40/wwvb.cfm> > > the way they did it will raise havoc with the synchronous AGC AM > detection schemes used in most old clocks, and in my old chip > design... > > <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> > > I'll have to muse over that and see if there's a solution. > > ...Jim Thompson >
A Costas loop, or failing that, a squaring loop as in the article. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On 3/15/2014 6:07 PM, Jeff Liebermann wrote:
> On Sat, 15 Mar 2014 11:04:22 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >> On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> >> wrote: >>> That was in late 2012 that WWVB added phase modulation and broke many >>> WWVB receivers. If that's your problem, there are a few fixes, but I >>> suspect they're only useful for higher end receivers. >>> <http://www.maxmcarter.com/rubidium/2012_mod/> > >> Aha! I didn't know about that phase modulation addition. Reading >> here.... >> <http://www.nist.gov/pml/div688/grp40/wwvb.cfm> >> the way they did it will raise havoc with the synchronous AGC AM >> detection schemes used in most old clocks, and in my old chip >> design... >> <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> >> I'll have to muse over that and see if there's a solution. >> ...Jim Thompson > > The addition of PM should NOT have broken a synchronous demodulator. > At worst, it should re-synchronize within one or two cycles.
Only if the loop bandwidth were at least 10 kHz, which it isn't. The
> shortest WWVB pulse is 200 msec wide or about 12,000 cycles of 60 KHz > carrier, which is plenty of time. I don't think your ancient chip has > a problem.
The maximum loop BW is set by the SNR. I sort of doubt it's that good.
> > <http://ka7oei.blogspot.com/2013/02/did-nist-break-bunch-of-radio.html> > <http://ka7oei.blogspot.com/2013/03/yes-nist-did-break-bunch-of-radio.html> > "Again, the ACTUAL problem with these clocks is that there appears > to be a bug in their own firmware/hardware that causes them to lose > the ability to re-synchronize themselves on their own, a problem > that appears to have manifested itself some time in mid/late 2012." > > Also: > WWVB Clocks don't sync anymore (revisited) > <http://www.febo.com/pipermail/time-nuts/2013-March/075111.html> > > I think you'll find the problem unique to a few specific products: > <https://sites.google.com/site/skyscan86715sync/home>
Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
>> anneal it first. (get it red-hot with a propane torch) >> then when it cools it'll be soft and can be formed by hand. > > ISTR You have to drop it in a bucket of water whilst red hot to make > copper stay soft (and avoid the jet of steam and boiling water).
I would do that sometimes to save time. it's not a required step. -- Neither the pheasant plucker, nor the pheasant plucker's son. --- news://freenews.netfront.net/ - complaints: news@netfront.net ---