Reply to message 6:............. .7300 de Dick W5UFZ How are leap seconds declared?
The International Earth Rotation and Reference System Service (IERS) observes the Earth's rotation and nearly 6 months in advance (January and July) a "Bulletin C" message is sent out, which reports whether or not to add a leap second in the end of June and December. --- On Mon, 7/28/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: From: [EMAIL PROTECTED] <[EMAIL PROTECTED]> Subject: time-nuts Digest, Vol 48, Issue 76 To: [email protected] Date: Monday, July 28, 2008, 5:09 PM Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [EMAIL PROTECTED] You can reach the person managing the list at [EMAIL PROTECTED] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: A fan for the Z3801A (Greg Burnett) 2. Low power GPSDO ([EMAIL PROTECTED]) 3. Re: time-nuts Digest, Vol 48, Issue 75 (Kit Scally) 4. Re: How to get 32.768KHz from 10MHz. (Neon John) 5. Re: How to get 32.768KHz from 10MHz. (Jim Lux) 6. Leap Second Pending (Mark Sims) 7. Re: How to get 32.768KHz from 10MHz. (Neville Michie) 8. Re: Leap Second Pending (Ken Winterling) 9. Re: How to get 32.768KHz from 10MHz. (Neon John) ---------------------------------------------------------------------- Message: 1 Date: Mon, 28 Jul 2008 11:11:01 -0600 From: "Greg Burnett" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] A fan for the Z3801A To: "Discussion of precise time and frequency measurement" <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="iso-8859-1" Another thing to consider: Depending on how well you shock-mount the fan, what if its vibration translates to sideband spurs or noise? -Greg ---------------------- Alberto wrote: Talking of the Z3801A, has anybody added a small fan to it ? Mine is very hot inside, especially the large VLSI chips on the upper board. I contemplated adding a couple of small DC fans, to push out the hot air, but first would like to know your opinions and your experiences, if any, about that. Thanks Alberto I2PHD ------------------------------ Message: 2 Date: Mon, 28 Jul 2008 17:04:03 EDT From: [EMAIL PROTECTED] Subject: [time-nuts] Low power GPSDO To: [EMAIL PROTECTED], [email protected] Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="US-ASCII" Hello Murray, no problem :) just wanted to make sure folks know that there are options below 5W out there. I am impressed with your 50mW TCXO unit. We've been thinking about offering DIP14 TCXO's as well on the FireFly. That would allow for true battery operation. We are also testing extremely low power (~120mW) OCXO's, with the heating elements integrated into the Crystal Blank itself, but I am not happy with the stability of these just yet. We also have a Fury GPSDO wired up to the Agilent E1938A - while it's the best Fury I have it's a real power hog. In fact I am having a hard time finding a power supply capable of delivering sufficient warmup current to that box.. bye, Said In a message dated 7/28/2008 11:33:44 Pacific Daylight Time, [EMAIL PROTECTED] writes: Jack, I didn't claim that the Trimble NTGS50AA was the "lowest power GPSDO". Those are your words. I simply said it was "at the other extreme", meaning (although not said) at the other extreme of my limited experience of about 10 different models. I own only five commercial GPSDOs (HP Z3801A; Symmetricom Z3815A with MTI 260 OCXO; CIC GPSR-A and Samsung GCRU-D with Rakon CFPO-2 OCXO; and the Trimble NTGS50AA), plus a working relationship with the Datum and Symmetricom units at work and a previously owned HP Z3815A with E1938A OCXO. I've also built a few, but not in the class of the commercial units. My lowest power one is battery operated (uses a V-TCXO) and has a power consumption of 50mW (with display backlight off!), but is more affected by sun load than is desirable. Another uses the HP 10811A OCXO, and can hardly be classed as low power. I have a professional interest in achieving low power in the GPSDO, as the company I work for are part of the Femtocell working group. I am certainly impressed that the Firefly is down at 1.35W. Regards, Murray Greenman **************Get fantasy football with free live scoring. Sign up for FanHouse Fantasy Football today. (http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020) ------------------------------ Message: 3 Date: Tue, 29 Jul 2008 08:56:24 +1000 From: "Kit Scally" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] time-nuts Digest, Vol 48, Issue 75 To: <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="us-ascii" Alberto, In the commercial world that the Z3815A's (and quite possibly the Z3801 etc) were used in, they were installed "vertically" at the bottom of a large equipment cabinet that had convection air channels running within it. A bank of 12-16 fans towards the top of the cabinet sucked up ambient air and forced it past the PA heatsinks. The hot air was vented out the PA modules & cabinet top. Ambient air temp was controlled at 20-25 deg C. The GPSDO pcb (and associated electronics) was cooled with incoming ambient air with the pcb and IC temperatures settling at some value. The critical point here is that the whole cabinet was operating 24x365 and for years on end. While semiconductor life is inversely proportional (?) to Tamb and cooling the electronics may seem a logical approach to prolonging life, I would suggest that <in this application>, this is a second-order effect. The killer is thermal cycling which can induce premature failure in any electronic assembly - passive or active - with everything else being equal. Most (if not all) of these commerciall modules were designed with very high MTBF's in mind when used "au natural". I would leave well alone and look into providing "standby power" to your Z3801. Regards, Kit VK2LL ************* Message: 3 Date: Mon, 28 Jul 2008 15:40:40 +0200 From: Alberto di Bene <[EMAIL PROTECTED]> Subject: Re: [time-nuts] A fan for the Z3801A To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Murray, thanks for the advice. Well, my intention was, as suggested by a private message, to use a 12V fan powered at 5V, so that it runs slowly and silently, not blowing external air into the unit, but just extracting the hot air from the inside. And given that the unit is placed in the basement of the house, with a change in temperature between the day and the night of no more than 1 Celsius, may be the use of the fan should not disturb the thermal regulation of the OCXO and the other temperature-sensitive devices, while at the same time lowering the working temperature of those hot ICs, thus prolonging (maybe) their life. Anyway I am open to comments and suggestions. Thanks 73 Alberto I2PHD -- ------------------------------ Message: 4 Date: Mon, 28 Jul 2008 19:22:37 -0400 From: Neon John <[EMAIL PROTECTED]> Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz. To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=us-ascii On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux <[EMAIL PROTECTED]> wrote: >At 03:01 PM 7/23/2008, Mike S wrote: >>You're missing the point. The application is to drive a common, readily >>available consumer clock. Simple and cheap. It can be done with a >>single $1 PIC. You could spend $20 or $100 and not get better results >>for the application. If you can describe a way of doing it for $0.50, >>please do. > > >But this is time-nuts... Any approach that doesn't have the >performance of a hydrogen maser or cryogenic sapphire resonator just >isn't good enough. Why, we haven't even started on how to build a >radial ruling engine to make sure the clock face is precisely divided >into 60 segments to ppb accuracy. Yep. There's turd polishing and then there is time nuts turd polishing. Going for the angstrom finish on the turd. The latter sometimes makes me grit my teeth.... > >Based on the clocks I've taken apart, dividing the 10MHz down to 1 Hz >is probably your best bet, rather than trying to hit 32768. However, >I don't know of a non-programmable single chip solution that will do >a divide by 1E7. If you want programmable chips, there's countless >ways, some more elegant than others. Seems to me that all the solutions proposed so far are a bit complex, trying to go for the 32khz frequency when that's not necessary. The quartz analog clockworks has a one or two winding stepper motor. The SIMPLEST solution is to drive those coils directly with the PIC output and scrap the rest of the circuitry. With some clever fiddling, one could use one of the 8 pin PICs and that WOULD get the solution cost down to around 50 cents :-) John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN Save the whales, collect the whole set! ------------------------------ Message: 5 Date: Mon, 28 Jul 2008 16:35:53 -0700 From: Jim Lux <[EMAIL PROTECTED]> Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz. To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="us-ascii"; format=flowed At 04:22 PM 7/28/2008, you wrote: >On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux <[EMAIL PROTECTED]> wrote: > > > > > >Based on the clocks I've taken apart, dividing the 10MHz down to 1 Hz > >is probably your best bet, rather than trying to hit 32768. However, > >I don't know of a non-programmable single chip solution that will do > >a divide by 1E7. If you want programmable chips, there's countless > >ways, some more elegant than others. > >Seems to me that all the solutions proposed so far are a bit complex, trying >to go for the 32khz frequency when that's not necessary. The quartz analog >clockworks has a one or two winding stepper motor. The SIMPLEST solution is >to drive those coils directly with the PIC output and scrap the rest of the >circuitry. Actually, it's not even that complex... it's often an electromagnet/solenoid driving a conventional escapement type clock mechanism. Why use 2 coils when you don't ever need to go backwards? One advantage of generating 32kHz (averaged over 1 second) is that you don't have to build the power driver stage to actuate that electromagnet.. (since it's built into the single dirt-cheap chip in the clock in the first place) >With some clever fiddling, one could use one of the 8 pin PICs and that WOULD >get the solution cost down to around 50 cents :-) And, one could probably figure out a way to use the original 32kHz crystal AND run at different speeds.. ------------------------------ Message: 6 Date: Tue, 29 Jul 2008 00:01:24 +0000 From: Mark Sims <[EMAIL PROTECTED]> Subject: [time-nuts] Leap Second Pending To: <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="iso-8859-1" My Thunderbolts have just raised the "Leapsecond Pending" minor alarm... six months seems a bit early for such a warning... ---------------------------------------- _________________________________________________________________ Stay in touch when you're away with Windows Live Messenger. http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_messenger2_072008 ------------------------------ Message: 7 Date: Tue, 29 Jul 2008 10:04:46 +1000 From: Neville Michie <[EMAIL PROTECTED]> Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz. To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed FYI, Quartz analogue clocks almost universally use a bipolar motor, a two pole magnetic circuit with the minimum reluctance axis displaced from the direction of the energised field. When activated the 2 pole magnetic rotor aligns with the magnetic field, when the field collapses, the magnetic rotor moves a little towards the position of greater self attraction, so that it is set up for a move in the right direction when the reverse field is applied. To drive these motors as clock displays you either replicate the alternate 1.5 volt 20mS pulses, or connect a capacitor, about 10 - 100 mfd in series and drive them with a 0.5 hertz square wave of about 1.5 volt amplitude. The drive voltage and pulse duration should be adjusted for each type of motor, or else the voltage and capacitor size so that reliable stepping occurs. Overdrive can stop some types as the rotor "poles". just in case you were interested, cheers, Neville Michie On 29/07/2008, at 9:35 AM, Jim Lux wrote: > At 04:22 PM 7/28/2008, you wrote: >> On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux >> <[EMAIL PROTECTED]> wrote: >> >> >>> >>> Based on the clocks I've taken apart, dividing the 10MHz down to >>> 1 Hz >>> is probably your best bet, rather than trying to hit 32768. However, >>> I don't know of a non-programmable single chip solution that will do >>> a divide by 1E7. If you want programmable chips, there's countless >>> ways, some more elegant than others. >> >> Seems to me that all the solutions proposed so far are a bit >> complex, trying >> to go for the 32khz frequency when that's not necessary. The >> quartz analog >> clockworks has a one or two winding stepper motor. The SIMPLEST >> solution is >> to drive those coils directly with the PIC output and scrap the >> rest of the >> circuitry. > Actually, it's not even that complex... it's often an > electromagnet/solenoid driving a conventional escapement type clock > mechanism. Why use 2 coils when you don't ever need to go backwards? > > One advantage of generating 32kHz (averaged over 1 second) is that > you don't have to build the power driver stage to actuate that > electromagnet.. (since it's built into the single dirt-cheap chip in > the clock in the first place) > > >> With some clever fiddling, one could use one of the 8 pin PICs and >> that WOULD >> get the solution cost down to around 50 cents :-) > > > And, one could probably figure out a way to use the original 32kHz > crystal AND run at different speeds.. > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. ------------------------------ Message: 8 Date: Mon, 28 Jul 2008 20:05:25 -0400 From: "Ken Winterling" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Leap Second Pending To: "Discussion of precise time and frequency measurement" <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=UTF-8 So has mine. Ken, WA2LBI On Mon, Jul 28, 2008 at 8:01 PM, Mark Sims <[EMAIL PROTECTED]> wrote: > > My Thunderbolts have just raised the "Leapsecond Pending" minor alarm... > six months seems a bit early for such a warning... > ---------------------------------------- > ------------------------------ Message: 9 Date: Mon, 28 Jul 2008 20:08:58 -0400 From: Neon John <[EMAIL PROTECTED]> Subject: Re: [time-nuts] How to get 32.768KHz from 10MHz. To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=us-ascii On Mon, 28 Jul 2008 16:35:53 -0700, Jim Lux <[EMAIL PROTECTED]> wrote: >>Seems to me that all the solutions proposed so far are a bit complex, trying >>to go for the 32khz frequency when that's not necessary. The quartz analog >>clockworks has a one or two winding stepper motor. The SIMPLEST solution is >>to drive those coils directly with the PIC output and scrap the rest of the >>circuitry. > >Actually, it's not even that complex... it's often an >electromagnet/solenoid driving a conventional escapement type clock >mechanism. Why use 2 coils when you don't ever need to go backwards? The clockworks that I've taken apart almost all have 2 coils. One brand has one. They all drive a permanent magnet rotor that turns 90 degrees on each tick. I'm not sure what the single coil design does to make sure the rotor always turns the right direction. Or maybe it doesn't matter if the rotor turns a cam and ratchet mechanism. I've never taken one apart far enough to know. > >One advantage of generating 32kHz (averaged over 1 second) is that >you don't have to build the power driver stage to actuate that >electromagnet.. (since it's built into the single dirt-cheap chip in >the clock in the first place) No driver needed. Each coil has about a bazillion (bazillion.000000 for time nuts) turns of wire so fine I can't see it without my 7x OptiVisor. I've never bothered to measure but the resistance has to be in the hundreds of ohms or more. It has to be that high to get over a year's operation from an AA battery. Duck soup for a PIC output pin driver. Funny how this works. I've been thinking about this same type problem for a few days independent of reading this list. I'm old-fashioned and like analog clocks much better than digital. I also like the precision of radio-controlled clocks. I've bought several different WWVB analog clocks, all of which seem to use the same cheap ChiCom movement. They uniformly suck (to use a technical term) at receiving WWVB where I live. The digital versions have no problem receiving but I don't like the looks. What I've been thinking about is a modern version of the Simplex master/slave clock system. A GPS disciplined master clock sending out operating pulses to slave clocks around my house and shop. I thought about wireless, including synthesizing my own WWVB signal but I know that I'll not get enough round tuits to do that. What I'm working toward is just about what I described above, except that the master clock will drive 4 conductor telephone station wire and the slave clocks will contain no electronics. Only the clockwork and the coils. All the clocks will be wired in parallel. This is an open-loop system that assumes all the clocks are in the same mechanical position when the master is activated. Perfectly acceptable, given the relatively few number of clocks and the small area involved. This architecture should give me what I want - REALLY simple, no electronics in the individual clocks, "atomic" accuracy, automatic DST correction and perfect synchronism. Comments? John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN No one can be right all of the time, but it helps to be right most of the time. -Robert Half ------------------------------ _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 48, Issue 76 ***************************************** _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
