andrew@kean.mun.ca (07/26/89)
I can't really speak for anyone else on the net, but one of the things that I really hate is clocks that are "just a little bit off". Now, a few years ago, I remember seeing a Heathkit (read:expensive) project for "the world's most accurate clock". Apparantly the thing picked up a broadcast from the NBS and decoded it. What a lovely thing for my PC... "this file created on 22-Jul-89 10:59:03.4 _EXACTLY_" :-) So the question... anyone know how this works and how/where it is broadcast? -Andrew. Bitnet: andrew@kean.mun.ca
tjk@csd4.milw.wisc.edu (Thomas Krueger) (07/27/89)
In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: >Now, a few years ago, I remember seeing a Heathkit (read:expensive) project for >"the world's most accurate clock". Apparantly the thing picked up a broadcast >from the NBS and decoded it. > >What a lovely thing for my PC... "this file created on 22-Jul-89 10:59:03.4 >_EXACTLY_" :-) > >So the question... anyone know how this works and how/where it is broadcast? We have two of them here at UWM. There are two shortwave radio stations, WWV in Fort Collins, CO, and WWVH in Honolulu. They both broadcast on 2.5, 5, 10, 15 and 20 MHz. The signal has two subcarriers, one at 100 Hz, and another at 1000 Hz, that contain data the clock decodes. The clock itself is the Heathkit GC-1000 "Most Accurate Clock". It receives on 5, 10 and 15 MHz, and will hunt for the strongest signal. When it receives two time frames that are the same (except for the obvious difference) the clock will update and be accurate to the nearest .1s. Supposedly the local oscillator will adjust itself up and down to agree with WWV. The clock has switches for GMT/local time, daylight savings (I think), delay propogation, channel lockout, and timezone. The RS-232 board is an "option" so better order it with the clock. Caveat: Don't connect this sucker to an external antenna that lightning likes to strike since you will blow the living piss out of the front end. In a house, the supplied whip antenna should be all you need. After blowing up both of these clocks many times, we connected the antenna to building ground... works fine. If you REALLY want to see the data stream, call 414-229-5955 at 1200 baud and when the PACX switch asks you what system, type "clock" then return (of course). Hope this helps. - Tom -- "A Veteran of the Psychic Wars" Thomas Krueger, Univ WI Milwaukee College of Engineering Electronics Shop tjk@csd4.milw.wisc.edu [moderator, info-high-audio] +1 414 229 5172
htaylor@pilot.njin.net (Hal Taylor) (07/27/89)
The National Institute of Standards & Technology offers an Automated Computer Time Service (ACTS). They offer a disk and instructions for $34.00. Order from: NIST Office of Standard Reference Materials B311 - Chemistry Bldg. NIST Gaithersburg, MD 20899 (301) 975-6776
usenet@cps3xx.UUCP (Usenet file owner) (07/28/89)
I remember an article in either _Radio Electronics_ or _Modern Electronics_ describing how to build an accurate timebase using the NBS standard clock. If I recall correctly it used a modified weather radio to pick up the broadcast. Hope this helps...
suzy@tank.uchicago.edu (suzy marie mercer) (07/28/89)
I know the original posting referred to a "PC," so this response probably isn't helpful for the little blue side of the world, but there is a PD program for the Mac called Set Clock. It calls up a time service and resets the system clock. The call takes a minute or less and costs about 10-15 cents off peak.
cook@stout.ucar.edu (Forrest Cook) (07/28/89)
In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: >I can't really speak for anyone else on the net, but one of the things that I >really hate is clocks that are "just a little bit off". ... >So the question... anyone know how this works and how/where it is broadcast? You are in luck, Andrew. NIST (the National Institute of Science and Technology, formerly NBS) has a telephone number that you can dial up with your modem and get accurate time info from. For more info write to: NBS-ACTS Time and Frequency Division Mail Stop 524 325 Broadway Boulder, Co. 80303 They also distribute a DOS compatible 360K 5 1/4" disk that can be used to set your PC. The cost: $35.00 from: NBS Office of Standard Reference Materials B311-Chemistry Bldg, NBS Gaithersburg, MD, 20899 (301) 975-6776 I wrote a simple program on our local VAX/VMS system that calls NIST once every night and corrects the system clock. Our time is usually within +- 1 second of NIST time. The last report I heard (about a year ago) was that they were talking about adding a 900 number. ^ ^ Forrest Cook - Beware of programmers who carry screwdrivers - LB /|\ /|\ cook@stout.ucar.edu (The preceeding was all my OPINION) /|\ /|\ {husc6|rutgers|ames|gatech}!ncar!stout!cook /|\ /|\ {uunet|ucbvax|allegra|cbosgd}!nbires!ncar!stout!cook
pmj@warwick.UUCP (Paul M Jaggard) (07/28/89)
Just in case anyone's interested...
In the UK, one source of accurate time information is the Rugby MSF
transmitter on 60kHz (VLF). The signal gives information on minute, hour,
day, date, month, year, and whether BST is in use or not. Data is transmitted
in fast-code, as well as in slow-code format (1 bit per second, so decoding is
fairly simple for even slow, home-made gadgets). Transmission range is in the
order of a few hundred miles.
Paul.
------------------------------------------------------------------------------
Paul Jaggard Chief Engineer, W963 Radio... ( ( ( | ) ) )
pmj@cs.warwick.ac.uk ...and occasional CS student |
Warwick University 0203-675656 (home) 0203-417220 x44 (W963) /|\
Coventry 0203-633933 x??? (work) //|\\
----------------------------------------------------------------- 963kHz AM --flash@lopez.UUCP (Gary Bourgois) (07/28/89)
> ... >>So the question... anyone know how this works and how/where it is broadcast? I have seen several clocks using the NBS signal, made for the BROADCASTING industry. BUT the best and simplest system (THE ONE I USE) is to tune your shortwave receiver to WWV, The National Bureau of Standards TIME STATION. They are loud and clear 24 hours a day on one of these standard frequencies: 2.5 5 10 15 20 Megahertz.... In addition to the time, the station provides other information, including solar terrestrial conditions (affects reception, power grids, computers) North Atlantic Weather... AND an audio pitch of 440hz so you can tune your piano (middle C) The radio frequencies of the actual transmissions are accurate to cesium standards (a couple parts per million or so), and can be used to calibrate your digital radio equipment. Nifty station! Time announcement is given once every minute. Just issue the time command, and sit there with your finger on the return key and smush it at the appropriate beep. Do all the clocks in your house with WWV... There is nothing so nifty as seeing the VCR, Microwave, Wristwatch, Computer display, etc all blink over at the same second. (however, after a few days, varying factors will cause them to go out of synch, and it will drive you insane...)
john@stiatl.UUCP (John DeArmond) (07/28/89)
In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: >Now, a few years ago, I remember seeing a Heathkit (read:expensive) project for >"the world's most accurate clock". Apparantly the thing picked up a broadcast >from the NBS and decoded it. > >So the question... anyone know how this works and how/where it is broadcast? > Someone else can probably comment on the nitty-gritty of the time code protocol. Since I own one of the Heathkit clocks (40 bux at a H-K surplus sale :-), I can comment on its use from a user perspective. The time code is encoded on the audio of all WWV & WWVH broadcasts. It is (i think) a component of the tick audio. The heathkit clock scans the 5, 10, & 15 mhz frequencies and picks the best. The clock has a "data" led that indicates when it is receiving valid data. There is also an LED to indicate "super accurate" mode. That is, the clock is synchronized with the broadcast. Even in the absence of a broadcast, the clock continues to run but not to specification. The clock displays one-hundreths of seconds. IT also has an RS-232 port that outputs the time in ascii each second. Funny, the output is not synchronized to the time code. The clock has dip switches on the bottom for setting propagation delay compensation. Since I don't know know how to calculate this, not having gotten a manual, I just set it to midway and forget it. The receiver in the Heath unit is very poor. I had to erect a large dipole to get a signal under any condition. Even with this antenna, I cannot receive the signal if a computer is on in the shack. If you find one of these clocks surplus, it is a pretty good deal. It IS nice to have The Time at all times. -- John De Armond, WD4OQC | Manual? ... What manual ?!? Sales Technologies, Inc. Atlanta, GA | This is Unix, My son, You ...!gatech!stiatl!john **I am the NRA** | just GOTTA Know!!!
psfales@cbnewsc.ATT.COM (Peter Fales) (07/28/89)
In article <8720@kean.mun.ca>, andrew@kean.mun.ca writes: > I can't really speak for anyone else on the net, but one of the things that I > really hate is clocks that are "just a little bit off". > Several people have mentioned the "dial up" nbs time. While this may be a little more expensive (in the long run) than picking up free radio signals, it is certainly convenient: All it takes is a modem and some software. I have my UNIX systems using a program posted to the net a while back which calls the nbs time every Sunday morning and sets the clock. I usually find the clock is off by 10-20 seconds over a week and the phone calls run about 13 cents. -- Peter Fales AT&T, Room 5B-420 2000 N. Naperville Rd. UUCP: ...att!peter.fales Naperville, IL 60566 Domain: peter.fales@att.com work: (312) 979-8031
tjk@csd4.milw.wisc.edu (Thomas Krueger) (07/28/89)
In article <723@lopez.UUCP> flash@lopez.UUCP (Gary Bourgois) writes: } }In addition to the time, the station provides other information, including }solar terrestrial conditions (affects reception, power grids, computers) }North Atlantic Weather... AND an audio pitch of 440hz so you can tune your }piano (middle C) 440 Hz is A below middle C. - Tom -- "A Veteran of the Psychic Wars" Thomas Krueger, Univ WI Milwaukee College of Engineering Electronics Shop tjk@csd4.milw.wisc.edu [moderator, info-high-audio] +1 414 229 5172
bill@videovax.tv.Tek.com (William K. McFadden) (07/29/89)
In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: >I can't really speak for anyone else on the net, but one of the things that I >really hate is clocks that are "just a little bit off". Yep. Me too. >Now, a few years ago, I remember seeing a Heathkit (read:expensive) project >for "the world's most accurate clock". Apparantly the thing picked up a >broadcast from the NBS and decoded it. >So the question... anyone know how this works and how/where it is broadcast? I have built one of these clocks, so I guess that makes me as qualified as the next person to talk about it. The clock has a tuner that picks up the WWV shortwave broadcasts on 5, 10, and 15 MHz. There is a 3-bit ADC that senses the AGC voltage in the receiver and tells the microprocessor how strong the station is. When first turned on, the clock will tune itself to each of the frequencies to see which one has the strongest signal. (You can lock out any of the channels if you have local interference on one of the frequencies.) After sampling the three frequencies the clock listens to the strongest one for a while. If it hears a 1 KHz tone (broadcast once per minute), it begins decoding the time data. The time data is broadcast as trinary, one bit per second. The three states are: zero, one, and data separator. The carrier is a 100 Hz tone. The duration of the tone determines the data value. The time and date are transmitted once per minute, as well as some bits designating daylight savings time, UT1 (astronomical time) correction, etc. Becauce of fading, the data can get corrupted quite easily, and the time code contains no error detection or correction bits (it's an OLD format). To combat this, the clock requires three minutes of good data before it sets itself. Thereafter, it keeps itself synchronized to the 1 KHz tone (1200 Hz for WWVH Hawaii; the clock can be set to recognize either, but not both at once). The clock's timebase is a 3.6 MHz 10 ppm crystal oscillator. It compares the drift of this oscillator to the WWV tones and continually trims it with an DAC-driven varactor (8 bits). This makes the oscillator (whose output is available on the back panel) very accurate over the long term. The short term accuracy is less, but the documentation does not say how much so. In cases where the drift is severe (e.g., when WWV reception is bad for a long time), upon regaining signal the clock will just update its time before beginning to trim the oscillator frequency. If reception is poor for more than a day or two, the 0.1 sec. digit in the display will be blanked, indicating the drift is probably greater than 0.1 second. When a given frequency is received, the clock will stay there as long as it can hear the 1 KHz tone each minute and properly decode some number (unknown to me) of the data bits. Also, if all the time bits are correct, it will not change frequency for at least 10 minutes. This is the "hi-spec" mode, which means the clock is within 0.01 seconds of WWV. In my area (Northwest Unites States), I can get the clock to stay in "hi-spec" mode for most of the day (with a longwire antenna). When the clock has determined the signal is too weak, it will sample the three frequencies again. If another is stronger, it will go there; otherwise it goes back to the original one. It repeats this until it has "locked on" to another strong signal. The bottom of the clock has dip switches that allow you to select 12/24 hour mode, GMT only, timezone selection, channel lockout, propagation time compensation (to compensate for the time it takes the signal to reach you), UT1 (astronmical time) correction, and automatic daylight savings time correction. On the back is an optional RS-232 jack, an on-off volume control for listening to the WWV receiver (can be set to turn on the speaker only when in "hi-spec" mode), an external antenna input, the 3.6 MHz output, an external 12 VDC input, and the AC power cord. On the top is a removable telescoping antenna (only good for strong signal areas), and on the side is a switch to turn off the display (to save power). The display consists of 6 digits for hh:mm:ss and a smaller digit for tenths of a second. There are AM/PM LEDs for 12-hour mode. To the right are three LEDs that indicate the receive frequency (5/10/15 MHz). Below these are LEDs labeled CAPTURE, DATA, and HI-SPEC. The CAPTURE LED indicates a valid WWV signal is being received. As long as this is lit, the clock will not change frequencies. The DATA LED flashes to the 100 Hz data pulses. You can tell a lot about the signal quality by watching this LED. The HI-SPEC LED is only lit when the clock thinks it's within 10 mS of WWV time. The optional RS-232 accessary outputs the time and date in ASCII form. A dip switch inside the clock selects the year (not supplied by WWV) and the baud rate. You can also select whether to transmit the data continuously (once per second) or on demand (e.g., when the computer asks for it). I really like this clock. Currently we're using it at work to synchronize our VAX. Our software for doing this is still a little buggy, though. (In fact, right now our software's not being used until someone has time to fix it). I have only a few complaints about the clock. First on the list would have to be the RS-232 interface, which seems to be more of an afterthought than an original design consideration. For example, the time is always 1 second off (they explain this in the manual, but don't tell why). Also, it is correct only at the beginning of the first character transmitted. Hence, you have to compensate for transmission time, which is dependent on baud rate. In addition, the output levels are 0 volts and 5 volts. Some systems (such as our VAX) complain about these levels because they are not valid RS-232. The second problem is a couple of times it has set itself to the wrong time. Apparently the same bit was wrong three times in a row, and the other data bits were correct. Thus, the clock assumed it was receiving correct time code. This has happened rarely and only at powerup, however, and the clock has always recovered in a few hours or less. Once it knows the correct time, it stays there. The third problem is there is no way to set the time manually. I can understand this because it would be difficult to do, and there is a DC power input that automatically switches in when the AC fails. However, if power is interrupted you can expect it to take anywhere from 5 minutes to a day to reset itself, depending on signal reception conditions. (The display will be blanked until the clock sets itself.) The last problem concerns quality control. The radio receiver board comes pre-assembled and tested. Unfortunately, two connections were not soldered on the board. This caused it to stop working about a year after I built it. It has worked fine since I soldered these two points, however. The kit cost around $300 and I was able to build it in two (long) evenings. BTW, most of my information comes from the manual that came with the clock. It has a good description of the WWV signal format and thoroughly describes the operation of clock hardware and software. If you need more info about the clock, contact me by e-mail, and I'll look it up. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 UUCP: bill@videovax.Tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill GTE: (503) 627-6920 "The biggest difference between developing a missle component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI
andrew@kean.mun.ca (07/29/89)
It turns out that "Reference Data for Radio Engineers" (Howard & Sams) lists the specs of all time data transmission. The whole thing may be moot, though, as no matter what time of day it is, I can't seem to pick up WWV, WWVH, WWVB, or WWVL here in Sunny (ha!) Newfoundland for longer than 15 min/day. Of course, I _do_ have a _real_ cheapie reciever... but I can't even pick up CHU in Ottawa (which, BTW, the book does _not_ say how to decode... but at least it gives a reference). Oh well. Maybe the "tick, tick, tick, ... ... ... BEEP" (insert finger smush on button here) approach is the simplest. On second thought.... nah. All that means is that I need to think about this some more. Anyone have a cheap (read: < $50.00 ) hydrogen maser for sale? -Andrew.
erk@americ.UUCP (Erick Parsons) (07/30/89)
From: suzy@tank.uchicago.edu (suzy marie mercer) Message-ID: <4684@tank.uchicago.edu> >I know the original posting referred to a "PC," so this response >probably isn't helpful for the little blue side of the world, but there >is a PD program for the Mac called Set Clock. It calls up a time >service and resets the system clock. The call takes a minute or less >and costs about 10-15 cents off peak. Not to rub salt but just to inform, there is also a PD program on these lines for the Amiga. It calls the Naval observatory in Washington D.C. and (compensating for time zone differances) sets the internal clock. I use it once a month via a cron time implemented command at a cost of about .87 a month (off peak rates). Can someone tell me if there is a service of this kind on the West Coast ?? What is the number ? -- ------------------ // -----------Cut-Here---------------------------------- Erick Parsons // Words for the wise: *If it works don't fix it.* Sacramento Ca // mail to: ...pacbell!sactoh0!americ!erk ------------- \\// --------------------------------------------------------
woolsey@nsc.nsc.com (Jeff Woolsey) (08/01/89)
In article <5502@videovax.tv.Tek.com> bill@videovax.tv.tek.com (William K. McFadden) writes: >In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: >>I can't really speak for anyone else on the net, but one of the things that I >>really hate is clocks that are "just a little bit off". Indeed. The clock in my car stops running (but remembers the time) whenever I crank the engine... >I have built one of these clocks, so I guess that makes me as qualified as the >next person to talk about it. I built one about four years ago, too. >The clock's timebase is a 3.6 MHz 10 ppm crystal oscillator. It compares the >drift of this oscillator to the WWV tones and continually trims it with an >DAC-driven varactor (8 bits). This makes the oscillator (whose output is >available on the back panel) very accurate over the long term. The short term >accuracy is less, but the documentation does not say how much so. But obviously the oscillator isn't going to get any more accurate after the eighth time the clock sets itself. That can happen within an hour if you have a good signal. >The bottom of the clock has dip switches that allow you to select 12/24 hour >mode, GMT only, timezone selection, channel lockout, propagation time >compensation (to compensate for the time it takes the signal to reach you), >UT1 (astronmical time) correction, and automatic daylight savings time >correction. I have yet to see any such clock that does the DST correction properly, i.e. applies it at 2AM local time. All of the clocks I have seen simply apply the bit in the time code when they see it. At WWV, this bit is a toggle switch that the operator flips as close to 0000Z on the prescribed day as is possible. Sometimes they forget. >I have only a few complaints about the clock. First on the list would >have to be the RS-232 interface, which seems to be more of an >afterthought than an original design consideration. For example, the >time is always 1 second off (they explain this in the manual, but don't >tell why). I've found that this one-second delay can be eliminated temporarily by the proper application of a finger across some CPU pins. The delay is missing in my clock due to CPU replacement (see below). >Also, it is correct only at the beginning of the first character >transmitted. Hence, you have to compensate for transmission time, >which is dependent on baud rate. It has to be correct somewhere. The best spot would be a marker after sending the time, but as it is, you could read your local clock at the start, collect the data which tells you what time the mark was, reread your clock for the delta from the mark, add the difference, and reset your clock. This assumes that the read-add-reset sequence for your local clock takes negligible time. >In addition, the output levels are 0 volts and 5 volts. Some systems >(such as our VAX) complain about these levels because they are not valid >RS-232. Indeed RS-232 standards are not met, but those aren't the actual output levels. Ground (pin 7) is at 5 volts, so that they can swing a 12V TxD line and it will go negative (relatively) more than 3 volts, so it is sort of within the realm of RS-232 operability. >The second problem is a couple of times it has set itself to the wrong >time. Apparently the same bit was wrong three times in a row, and the >other data bits were correct. Thus, the clock assumed it was receiving >correct time code. This has happened rarely and only at powerup, >however, and the clock has always recovered in a few hours or less. >Once it knows the correct time, it stays there. This is now a known problem, not limited to power-up. My clock did that a couple of times, and after some correspondence with Heathkit they sent me a replacement CPU (with a piggy-back 2716), and the problem has not recurred. At the same time, the 1-second delay in the ASCII time disappeared with this CPU. >The third problem is there is no way to set the time manually. I can >understand this because it would be difficult to do, and there is a DC >power input that automatically switches in when the AC fails. However, >if power is interrupted you can expect it to take anywhere from 5 >minutes to a day to reset itself, depending on signal reception >conditions. (The display will be blanked until the clock sets itself.) There is a way to set the time manually. Inside the clock there is a test switch which was used to calibrate the 1000/1200 Hz decoder. Push the switch a few more times and you get to read/advance the day of year, hour, minute, and perhaps second (it's been a while, I don't remember). I do not trust my clock after this exercise until the time agrees with the audio once again, because I think the HI SPEC LED remains lit if you do this. Check it out. >The last problem concerns quality control. The radio receiver board >comes pre-assembled and tested. Unfortunately, two connections were not >soldered on the board. This caused it to stop working about a year >after I built it. It has worked fine since I soldered these two points, >however. After four years of owning this clock, I finally got it to listen to 15MHz yesterday. It had NEVER set on this freq before, and turning the volume up after forcing the clock to listen to 15 MHz yielded silence. So I poked at the receiver board with a scope, and lo and behold that particular band started working. Perhaps I reseated a loose crystal or something. Subsequently I haven't seen the clock set on anything but 15 MHz, it likes that so much. We'll see if the shock of an upcoming move upsets it. I do have a wish list for clocks of this ilk, including the ability to ask it things. There are numerous other design problems with the Heathkit clock along the lines of the year DIP switches (such as not knowing for which time-zone the clock is reporting times without looking at the bottom of the clock--the computer cannot find out). PSTI (Precision Standard Time Interfaces? (now defunct, I hear)) was a little better in this regard, but still not perfect. -- -- Qualify nearly everything. Jeff Woolsey woolsey@nsc.NSC.COM +1 408 721-8162
jad@dayton.UUCP (J. Deters) (08/01/89)
In article <723@lopez.UUCP> flash@lopez.UUCP (Gary Bourgois) writes: [article on synchronizing clocks deleted] > >Do all the clocks in your house with WWV... There is nothing so nifty as >seeing the VCR, Microwave, Wristwatch, Computer display, etc all blink over >at the same second. (however, after a few days, varying factors will cause >them to go out of synch, and it will drive you insane...) Reminds me of a [supposedly] Confucius proverb: Man with one watch always knows what time it is. Man with two watches is never sure. -j -- J. Deters - jad@dayton.DHDSC.MN.ORG "I'll tell you what kind of guy I was. If you ordered a boxcar full of sons-of-bitches and opened the door and only found me inside, you could consider the order filled." -- Robert Mitchum
todd@ivucsb.sba.ca.us (Todd Day) (08/01/89)
erk@americ.UUCP (Erick Parsons) writes:
~It calls the Naval observatory in Washington D.C.
~and (compensating for time zone differances) sets the internal clock. I
~use it once a month via a cron time implemented command at a cost of
~about .87 a month (off peak rates).
Who's your telephone carrier? It costs me .16 at night and .32 during
the dayon ATT. It only takes a couple seconds of connect to do the actual
clock setting.
--
Todd Day | todd@ivucsb.sba.ca.us | ivucsb!todd@anise.acc.com
"It's not the heat, it's the stupidity" --- Angry Poodle B-B-Qbill@videovax.tv.Tek.com (William K. McFadden) (08/01/89)
In article <13107@nsc.nsc.com> woolsey@nsc.nsc.com.UUCP (Jeff Woolsey) writes: ->In article <5502@videovax.tv.Tek.com> bill@videovax.tv.tek.com (William K. McFadden) writes: ->>The clock's timebase is a 3.6 MHz 10 ppm crystal oscillator. It compares the ->>drift of this oscillator to the WWV tones and continually trims it with an ->>DAC-driven varactor. This makes the oscillator very accurate over the long ->>term. ->But obviously the oscillator isn't going to get any more accurate after ->the eighth time the clock sets itself. That can happen within an hour ->if you have a good signal. What I meant was that, integrated over a long period of time, the timebase is very accurate. This is because it is always playing "catchup" with WWV. (However, this is NOT true if the drift is large and the clock has to reset itself.) An analogy I like to think of is line frequency. The power line may be slightly off frequency at a particular moment, but over the long run it averages out. ->I have yet to see any such clock that does the DST correction properly, ->i.e. applies it at 2AM local time. All of the clocks I have seen ->simply apply the bit in the time code when they see it. At WWV, this ->bit is a toggle switch that the operator flips as close to 0000Z on the ->prescribed day as is possible. Sometimes they forget. That's true. Another nit I forgot to mention. Having it change in mid- afternoon is a bummer. ->>I have only a few complaints about the clock. First on the list would ->>have to be the RS-232 interface, .... ->>... the output levels are 0 volts and 5 volts. ->Indeed RS-232 standards are not met, but those aren't the actual output ->levels. Ground (pin 7) is at 5 volts, so that they can swing a 12V TxD ->line and it will go negative (relatively) more than 3 volts, so it is ->sort of within the realm of RS-232 operability. Your clock must be different than mine because mine puts out 0 and 5 volts. The schematic says so and an oscilloscope said so. I built my clock in 1985, so I'm not sure if yours is newer. Anyway, I'm glad they fixed this. (Maybe I can modify mine.) ->>The second problem is a couple of times it has set itself to the wrong ->>time. ->This is now a known problem, not limited to power-up. My clock did ->that a couple of times, and after some correspondence with Heathkit they ->sent me a replacement CPU (with a piggy-back 2716), and the problem has ->not recurred. At the same time, the 1-second delay in the ASCII time ->disappeared with this CPU. Was it free? I would like to get this if it doesn't cost an arm and a leg. Have any idea how they fixed it? ->>The third problem is there is no way to set the time manually. ->There is a way to set the time manually. Inside the clock there is a ->test switch which was used to calibrate the 1000/1200 Hz decoder. Push ->the switch a few more times and you get to read/advance the day of ->year, hour, minute, and perhaps second .... Sounds like another new feature. I don't remember my clock having it. (Of course, it could be my memory that's at fault, and not the clock! :-) I guess it's time to call Heathkit and ask about a software upgrade. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 UUCP: bill@videovax.Tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill GTE: (503) 627-6920 "The biggest difference between developing a missle component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI
collinge@uvicctr.UVic.ca.UUCP (Doug Collinge) (08/02/89)
In article <3586@csd4.milw.wisc.edu> tjk@csd4.milw.wisc.edu (Thomas Krueger) writes: >In article <723@lopez.UUCP> flash@lopez.UUCP (Gary Bourgois) writes: >}AND an audio pitch of 440hz so you can tune your piano (middle C) >440 Hz is A below middle C. 440 Hz is A above middle C (262Hz), in case anyone cares who doesn't already know... -- Doug Collinge School of Music, University of Victoria, PO Box 1700, Victoria, B.C., Canada, V8W 2Y2 collinge@uvunix.BITNET decvax!uw-beaver!uvicctr!collinge ubc-vision!uvicctr!collinge __... ...__ _.. . ..._ . __... __. _. .._ ..._._
clements@bbn.com (Bob Clements) (08/02/89)
In article <2012@ubu.warwick.UUCP> pmj@cs.warwick.ac.uk (Paul Jaggard) writes: > In the UK, one source of accurate time information is the Rugby MSF >transmitter on 60kHz (VLF). [...] Transmission range is in the >order of a few hundred miles. In the US, we have the same sort of thing. It's called WWVB and it is also on 60 KHz. The code is similar to that on the 100 Hz subcarriers of WWV and WWVH, but not identical. I have a small receiver board for 60 KHz stashed somewhere. I used it for a while before the Heathkit clock came out. Since I'm located in the Boston area, the signal from Fort Collins Colorado and the signal from Rugby UK are about the same strength. Therefore the times when I can successfully receive the time code are pretty rare. I got a decent signal for a couple of hours per day, not every day. But in some parts of this country, the WWVB signal is more reliable than the WWV signals. As a matter of interest, WWVH in Hawaii synchronizes its time and frequency with the NBS clocks on the mainland by listening to WWVB on 60 KHz. When I've visited there I've seen the chart recorder showing phase differences between WWVB and a locally generated 60 KHz from their local generators. The difference was basically a 24-hour sine wave, but they watch for long term drift. The clocks at both WWV and WWVH are sets of three cesium clocks, each with their own time/RF/tone generators, continually voting among themselves. This is all in a shielded, temperature controlled room. The clocks are tweaked manually when necessary to match higher authority. WWVH to match WWV, WWV to match the big clocks in Boulder. When I first visited WWVH their only external reference was WWVB. More recently, they also compare against Loran C, Omega, and something else I don't recall. Maybe GPS. All the agencies watch each other and cooperate keeping this accurate. It's a neat place to visit. It's on the southwest corner of Kauai. In fact, it's a neat place even if you DON'T go to WWVH. :-) >pmj@cs.warwick.ac.uk Bob Clements, K1BC, clements@bbn.com
toddpw@tybalt.caltech.edu (Todd P. Whitesel) (08/02/89)
If i remember correctly, the one minute slip is caused by the fact that the one-bit-per-second message starts on the minute, but gives _that_ minute's time. So when you start receiving the message you should increment the clock and load it when the message has been received, this way the clock sets itself correctly but anticipates the next message while it is being received (assuming the next minute is the next one after the present one, always true except maybe for daylight savings). toddpw (Todd P Whitesel) @tybalt.caltech.edu
andrew@kean.mun.ca (08/04/89)
I'd like to thank everyone who responded for my quest for accurate time. BTW, since all my mail bounces, I'd like to ask erk@americ if he could email me that PD Amiga clock setter. Sigh. Someday this bounced mail grumble moan swear grumble.... -Andrew. <andrew@kean.mun.ca>
johng@trwind.UUCP (John Greene) (08/12/89)
In article <6142@stiatl.UUCP> john@stiatl.UUCP (John DeArmond) writes: >In article <8720@kean.mun.ca> andrew@kean.mun.ca writes: > >The clock displays one-hundreths of seconds. IT also has an RS-232 >port that outputs the time in ascii each second. Funny, the output is >not synchronized to the time code. Funny, mine is. > >The receiver in the Heath unit is very poor. I had to erect a large >dipole to get a signal under any condition. Even with this antenna, >I cannot receive the signal if a computer is on in the shack. > I don't have any problem with the receiver on mine. Maybe that is why you got such a good deal at the surplus place. I keep my antenna about 1.5 feet high and it lights the "most accurate" light almost every night. If I go to an external antenna or extend the rod antenna to its full extent, the "most accurate light is on for the majority of the time. -- John E. Greene "People are just like frankfurters....You have to decide if you're going to be a hot dog or just another wiener" DLR TRW Information Networks Division 23800 Hawthorne Blvd, Torrance CA 90505 ARPA: johng@trwind.ind.TRW.COM USENET: ..trwrb!trwind!johng