Re: [time-nuts] Primary Standards...
On 2/24/10 4:38 AM, Rob Kimberley r...@timing-consultants.com wrote: Yes, and no.. Time as we know it (UTC) is coordinated at the BIPM in Paris between observations from primary standards at contributing laboratories and also earth rotation measurements. Each lab contributing will at any time (excuse the pun) have a small time offset with regard to UTC. E.g. time from NPL in UK would say be offset from UTC at any time by a few microseconds, and would be designated UTC-NPL. Worth reading http://www.npl.co.uk/science-technology/time-frequency/time/ Interestingly there is a lot of research into more stable clocks using Mercury and Ytterbium. This then leads to discussion about a future possible re-definition of the second (which IMHO will happen). Yes... At JPL there's work going on with a linear trapped Hg ion clock for spacecraft. Stability is 1E-12/sqrt(tau), with temperature sensitivity on the order of 1E-15/degree (at the basic sensor). Roughly a liter in volume and 1 kg. When it's done, it will enable a lot of changes in things like navigating spacecraft and making precise measurements over long distances. (because you can do one-way measurements, as opposed to two way) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Fw: Rb Oscillator - rather fundamental question
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of WarrenS Sent: Tuesday, February 23, 2010 1:04 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Fw: Rb Oscillator - rather fundamental question One more try, As often happens when I rant, the rant is discarded in the posting. Rick Thanks, Interesting but maybe you have missed my too subtle of a point. Example: Lets say the second is redefined in the future to some new super duper thing that is good to 1 part in e20 (Which will happen if (when) the super duper thing becomes more available and proven) (Maybe based on the time it takes to count all the atoms in the new purposed 1 Kg sphere OR something like that.) Then the CS Osc would not be the BEST primary standard anymore, at least NOT at the new improved spec it could then be given. Not because it has changed or is less accurate, but because there is now something better. If it is not the primary standard, it does not make it worse, but it does mean it will now be a second standard at the new higher performance spec, by definition and need to be then calibrated and checked against the new primary standard IF one wanted to use it to it's maximum capability as a cost effective substitute for the supper duper. I don't think so.. In that event, the unobtainium and Cs sources would both be primary standards (within their random variation). The Cs+ standard would be less accurate than the Un+ standard, but they're both primary. The key to a primary standard is that if you build it, it requires no calibration against something else. It's like the meter, which is defined in terms of the wavelength of a particular spectral line in vacuum. Doesn't matter how you get the spectral line, but count off some number of wavelengths, and that's a meter. Now, could one argue that a Rb source is also a primary standard, just with low precision? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Primary standard again
** Primary means that the clock will meet its spec without being calibrated against a better clock** From your definition a Rb can be a primary standard for a 1e-6 world and a crystal as well as my wrist watch can be a primary standard in a 1e-3 spec or whatever they can repeat without Calibration. BUT I have not heard anyone argue that any of the above are primary standards, even at some reduced spec. (maybe just because not cost effective?) I suppose a pendulum can be a primary standard at some accuracy. Using the kit of parts analogy, if one builds the pendulum and operates it at sea level, the period of the pendulum is entirely determined by the physical dimensions and the gravitational constant. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Primary standard again
Aren't there relativistic effects on Cs standard frequency because of different gravity? (or is that really, the same frequency, just in a different frame of reference) -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Tuesday, February 23, 2010 1:43 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Primary standard again A REAL primary standard is something that you can assemble the kit of parts anywhere in the Universe, flip the switch, and get exactly the same time interval as anywhere else. That obviously does NOT apply to the pendulum, as it depends on the value of G. -John == I suppose a pendulum can be a primary standard at some accuracy. Using the kit of parts analogy, if one builds the pendulum and operates it at sea level, the period of the pendulum is entirely determined by the physical dimensions and the gravitational constant. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Primary Standards...
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Holmes, N8ZM Sent: Tuesday, February 23, 2010 4:57 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Primary Standards... My recollection of the definition of an Ampere is 6.02 x 10^23 electrons per second (Avogadro's Number, I believe) passing a point in a conductor. To this day, I wonder how they managed to count all those electrons. But it does suggest that the silver deposit approach might be a better method of building a standard. Seems, though, like you'd have to make a darned high resolution weight measurement. This is why Josephson junctions are useful. They have a frequency/voltage characteristic that is a fundamental property of physical constants. So, if you can measure frequency (using that primary standard for frequency or time), you can measure voltage. So, to measure current, you have to turn voltage into current somehow, And you could use the Quantum Hall Effect as resistance standard, which like the Josephson, relies on fundamental physical properties, and is independent of most of the construction details (assuming it works at all) You need a cryogenic system, and a high flux density (10 Tesla or so): http://www.warwick.ac.uk/~phsbm/qhe.htm ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Patents was: Re: Phase Noise of 74AC gates
On 2/19/10 8:49 PM, Rick Karlquist rich...@karlquist.com wrote: Bruce Griffiths wrote: He's made similar comments before. It actually isnt that difficult to achieve an isolation amplifier phase noise floor below -170dBc/Hz if one is careful to use appropriate parts, design techniques, and the input signal level is high enough. The real problem is verifying that performance. The 10811 production engineers searched for a long time for a low noise buffer amplifier and settled on the ANZAC AMC-123. The data sheet refers to a patent that reads like a construction article. You can make your own if you can find an old 2N5109 transistor. I love those kinds of patents! A friend's patent attorney was telling me that one way to help your patent app glide through is to write it that way. The examiners love to see practical details and test data. Much better to say a preferred embodiment uses a 1/4-20 bolt 3 long tightened to 50 inch pounds rather than a preferred embodiment uses a threaded fastener. Save the generic fastener for the claims. His comment was that once the patent issues, nobody can duplicate (legally) what you describe in your disclosure (assuming the claims were written to cover it), so why be coy and vague. He also said that a good disclosure makes your patent more likely to be cited by others as prior art, and hence, less likely to have those subsequent patents have claims that overlap yours. Now, I will confess that I have met other patent attorneys who like vague and coy, because that confuses people reading it, and you might be able to negotiate a better deal in a cross-licensing sort of situation. Naturally, of course, those attorneys assume you'll be hiring THEM to do that negotiation. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Advice on 10 MHz isolation/distribution (Clay)
-Original Message- Lastly, my customer, the system designer, would now like to be able to add a switch function to the 10 MHz distribution. I will have to check and see if switching of bias current to these two-stage transistor amp circuits can accomplish this function. Jelly-bean analog switches are unlikely, I think, to have the requisite noise and isolation performance. Nothing like hitting a moving target. Clay One way to achieve high isolation using analog switches is to use a T switch configuration. Or a SPDT relay. I don't know if they'd meet your vibe requirement, though. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone app
On 2/16/10 10:37 PM, Thomas A. Frank ka2...@cox.net wrote: I don't believe that there is a 1pps available to the OS. The GPS chipset seems to provide a very limited amount of data to the phone. For example, there does not appear to be any way to get satellite status info from the GPS chip to the OS. At least none of the apps I've tried thus far (and I've tried a fair number) provide anything like that. Tom Frank I would guess that the GPS is an assisted GPS and a lot of the smarts is in the cellular system (e.g. Satellite almanac, etc.). All the thing in the phone does is start with a presupplied estimate of position and get code phase for some subset of satellites, then do the nav calculation, most likely with help from the cellsite. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] iPhone app
On 2/17/10 6:45 AM, Lux, Jim (337C) james.p@jpl.nasa.gov wrote: On 2/16/10 10:37 PM, Thomas A. Frank ka2...@cox.net wrote: I don't believe that there is a 1pps available to the OS. The GPS chipset seems to provide a very limited amount of data to the phone. For example, there does not appear to be any way to get satellite status info from the GPS chip to the OS. At least none of the apps I've tried thus far (and I've tried a fair number) provide anything like that. Tom Frank I would guess that the GPS is an assisted GPS and a lot of the smarts is in the cellular system (e.g. Satellite almanac, etc.). All the thing in the phone does is start with a presupplied estimate of position and get code phase for some subset of satellites, then do the nav calculation, most likely with help from the cellsite. Most important to us GPS fanatics is of course the 3G iPhone¹s built-in GPS. As you can see from the picture, the new location-aware capabilities come from Infineon¹s PMB 2525 Hammerhead II chip. Accurate to within just a few meters, the Hammerhead II ³integrates an assisted-GPS (A-GPS) baseband processor with a low-noise GPS RF front end and multi-path mitigation to avoid large errors in urban environments². Some have said that the chip¹s die markings indicate that it¹s actually a Hammerhead I chip, but one analyst involved in the teardown http://www.eetimes.com/news/latest/showArticle.jhtml;jsessionid=ZCHQFCWAAIH R2QSNDLSCKHA?articleID=20914 says that it¹s common practice for a company to take an old chip and make routing and/or connection modifications and then label the modded chip ³new². http://gpsobsessed.com/3g-iphone-teardown-infineon-gets-built-in-gps-contrac t-not-broadcom/ Rummaging on infineon's website for the Hammerhead.. It's a tiny RF front end and correlator with a serial connection to the host processor. It takes a 32kHz backup osc and a reference osc from 10-40 MHz. I doubt that there's an output for any sort of code epoch or nav message. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DMTD to MMTD
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Wednesday, February 17, 2010 2:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DMTD to MMTD Lux, Jim (337C) wrote: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Wednesday, February 17, 2010 1:57 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] DMTD to MMTD Hi Thanks for the quick response. The impression I've always had of that system is that it is comparing the sources two at a time. They can select between a number of sources, but only one pair is looked at. It basically timestamps transitions on all 8 inputs. The post processing software that looks a the timestamps is what selects either 1 channel (single mixer+offset generator) or 2 channels (dual mixer time difference) The counters in the FPGA are running at 100 MHz, so they have a basic resolution of 10 ns. ___ See: http://tycho.usno.navy.mil/ptti/ptti2006/paper11.pdf That's basically the same as the IPN progress report you linked in the earlier email. Same figures, nicer typography, but the figures are better in the IPN progress report (169B). As it says, referring to the Counter Assembly: It latches the readings of a continuously-running 100 MHz counter at the zero-crossing times of all channels that have a valid signal present. The output is fed continuously into the computer's serial port with no flow control. Steve Cole doesn't show up in the phonebook, so I can't just call him for more details, but I could probably find a copy of the footnoted description. I'd actually be more interested in the design of the zero crosser. Seeing if one could get a copy of NPO-40468 from NASA Tech Briefs (if it was published there) might also be useful. Try this: http://www.techbriefs.com/component/content/738?task=view Or http://www.techbriefs.com/component/docman/doc_download/-progress-on-a-multichannel-dual-mixer-stability-analyzer those reference http://www.techbriefs.com/component/content/article/7326 http://www.techbriefs.com/component/docman/doc_download/1618-oscillator-stability-analyzer-based-on-a-time-tag-counter but there's nothing much new in that one.. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DMTD to MMTD
JPL have had such systems for many years: http://tmo.jpl.nasa.gov/progress_report/42-169/169B.pdfhttp://tmo.jpl.nasa.gov/progress_report/42- 169/169B.pdf http://tycho.usno.navy.mil/ptti/1994/Vol%2026_25.pdf Bruce Additional papers: http://tycho.usno.navy.mil/ptti/ptti2006/paper11.pdf That's basically the same paper as the http://tmo.jpl.nasa.gov/ reference above. http://tycho.usno.navy.mil/ptti/ptti2006/paper26.pdf That one just talks about the LITS standard, but doesn't describe any of the measurement technique, just results for the Hg+ ion clock. http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA485911Location=U2doc=GetTRDoc.pdf http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA485911Location=U2doc=GetTRDoc.pdf There's not a huge amount of information in that one, more high level block diagrams of how DSN does its synchronization and screen shots of the software. http://ipnpr.jpl.nasa.gov/progress_report/42-167/167C.pdf is a better description of the system. Rummaging through here: http://tmo.jpl.nasa.gov/index.cfm might be productive. A lot of the IPN progress reports (formerly TMO, TDA, or DSN progress reports) don't get indexed in the JPL Technical Reports Server or the NASA equivalent. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DMTD to MMTD
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Wednesday, February 17, 2010 4:20 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DMTD to MMTD Lux, Jim (337C) wrote: I don't know if there's a FIFO in front of the UART (e.g. what if you get simultaneous zero crossings).. but I would expect there is. The hard work is in the zero crossing detector ahead of the FPGA. (and perhaps in the latching of the ZCD inputs into the FPGA). Given how long ago it was made, that FPGA isn't a huge one. You've got 8 channels, each zerocrossing at about 200-300 Hz (the difference frequency is 123 or 124 Hz, so you get twice that many zero crossings), or about 1600-2400 messages/second. At 6 characters per message, that's about 10,000 characters per second, so you'd need a fairly fast UART to keep up. (OTOH, the article mentions dropping characters..) A LAN, USB or Firewire interface may be more appropriate all are easy to implement. Yes, but faster rise times and potentially more EMI. The FTL guys are pretty obsessive about stray noise sources. As far as interfaces.. if I were choosing, I'd use LAN (like pair a Rabbit with the FPGA.. the Rabbit does the UI as a static webserver kind of thing), although USB is ok, but ties the box to one computer. USB is cheaper though. Firewire/1394 is a dying standard... If you need speed, then GigE would probably be a better choice. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hands on digital clock
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Tuesday, February 16, 2010 4:25 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hands on digital clock It seems to me there is a way to make the segments folding so they could be changed without removing and inserting boards. Kind of like a folding ruler. I'll have to do some experiments with scraps of wood in my shop. On a smaller scale of course. Several years ago, I walked by one of the solar powered radar sets that shows you your speed on a pair of big 7 segment displays. It was clicking as the displayed speed changed so I stopped to look at it. The segments rotate about the long axis. So think of flipping the ruler segments over rather than folding them. Those are very nifty displays. I can't recall when I first saw them, but it has to have been back in the 80s or perhaps 70s. The display element is magnetized, and they have a coil behind it that gets either a positive or negative pulse to flip it. I seem to recall some sort of capacitor and SCR circuit was used. They're nice because they don't consume any power when not changing, and can be artificially illuminated as bright as you like. The signaling is pretty robust, so you can put the display at the end of a long wire, too. They aren't very fast, though. You couldn't display motion video. But for a time nut? Sure. You could carefully balance them for aerodynamics, and actuate them with floats and falling weights from your clepsydra, for instance. Some sort of fluidic water level to 7 segment decoder would be needed, but that could be very fun to design with buckets and counterweights (e.g. you make a 3 input AND gate with a bucket that holds 3 liters of water, counterweighted with a 2.5 kg weight) Hmm, you sort of inherently get a thermometer code from a clepsydra, so you need a thermometer to 7 segment decoder. I envision a giant jacquard loom or piano roll scheme, with holes to fill or drain the weights that turn the segments. Air pressure is also legal, I suppose. It kind of depends on whether you need it to be totally gravity driven, or whether a pump/compressor is ok. (If you've ever seen the Villa d'Este in Tivoli, near Rome, you'd be amazed at what can be done with air and water pressure, ALL gravity fed) http://en.wikipedia.org/wiki/Villa_d%27Este (which is actually a pretty lame description) google for villa d'este organ fountain and you'll turn up some youtube video. http://www.youtube.com/watch?v=gGJumf6m44M is one of them ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hands on digital clock
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, February 16, 2010 5:01 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hands on digital clock Lux, Jim (337C) wrote: (If you've ever seen the Villa d'Este in Tivoli, near Rome, you'd be amazed at what can be done with air and water pressure, ALL gravity fed) http://en.wikipedia.org/wiki/Villa_d%27Este (which is actually a pretty lame description) google for villa d'este organ fountain and you'll turn up some youtube video. http://www.youtube.com/watch?v=gGJumf6m44M is one of them As I recall it, it was an hours bus ride from Termini, so it is a nice day-activity to leave Rome and visit Villa d'Este and Tivoli. It was a bit cold when I was there over 20 years ago. About 2 hrs on the Metro and COTRAL bus. Big difference between getting the local and the express bus. The colder temperature is an advantage in the summer, when Rome is hot. That's why Hadrian built his palace up there, and later Pope Ippolito(?) did too. Hmm... fluidistor counter, BCD decoder feeding small sprinklers for fluid-digital display? PPS electrical input controlling a single electrical-to-air-burst conversion. GPS-controlled of-course. :) Should be possible to implement. :) Something like a pps (or ppminute) to tipping bucket to dump quanta of water into the clock is what I was thinking. Of course, a more sophisticated approach would be to use the pps to discipline a more conventional (as in what the Greeks used) continuous flow regulator (i.e. a constant level in a container and a small hole). You'd need to compensate for temperature effects on the orifice size and the viscosity of the water (maybe there's a clever way to self compensate? You want the hole bigger as it gets colder, because the water gets more viscous (in an exponential relationship, I think), otoh, it depends if your clepsydra is mass or volume driven) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Loran C sounds
On 2/14/10 12:54 PM, J. Forster j...@quik.com wrote: Power companies charge for KVAs, NOT KVARs. -John = Take a look at the poor (but commonly low) power factor. Much more volt-amps are being delivered than used to do effective work as kilowatts. Power factor correction would be a money saver if saving money were an objective. PF = 0.75 isn't horrible but not great. The apparent power is 33% more than the actual power. That's what lots of places with older motors and conventional fluorescent ballasts probably run. The electric company (at least here in southern california) doesn't charge for KVA or KVAR, per se. What they do is charge for kWhr, plus a penalty for poor PF, but the penalty isn't proportional to the VARs. It's more of a step function, based on the peak reactive load. (measured in some fairly small time increment) For instance, on Southern California Edison tariff RTP-3 Large Realtime pricing For service delivered and metered at voltages greater than 50kV, including Cogeneration and Small Power Production Customers, the billing will be increased by $0.18 per kilovar of maximum reactive demand imposed on the Company. (you get a 10%+ discount for getting your power at 50kV and above) For service delivered and metered at voltages of 50kV or less, including Cogeneration and Small Power Production Customers, the billing will be increased by $0.23 per kilovar of maximum reactive demand imposed on the Company. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Loran C sounds
On 2/14/10 1:05 PM, Stan, W1LE stanw...@verizon.net wrote: Residential meters measure KW Industrial meters usually measure KVARs along with KVAs delivered and the utility bills for both. There is usually a distinct economic factor to reduce KVARs Stan, W1LE The last place I worked where I had access to the meters, the KVAR meter had a peak hold feature (mechanical) that would remember the highest reactive load we drew. As described in another post, SoCal Edison tags you with a fee for whatever that peak hold read, on top of your kWhr number. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] CTS TCXO
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Marco IK1ODO Sent: Wednesday, February 10, 2010 1:09 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] CTS TCXO Hi all, I have a CTS Knights TCXO, P/N 970-3832-0. Frequency is 10 MHz. Anyone knows the working voltage? Date code is from 1987, too old for Internet :-) 73 - Marco IK1ODO Why not ask CTS? http://www.ctscorp.com/components/ http://www.ctscorp.com/feedback/techinfo.htm ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Injection locking
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Kit Scally Sent: Wednesday, February 10, 2010 3:55 PM To: time-nuts@febo.com Cc: Kit Scally Subject: [time-nuts] Injection locking Hi, As others have already noted, there's a paucity of circuits or down to earth advice on this topic - unless your poison is millimetre wave technology. I set out to GPS-lock my Icom 706 transceiver some while ago. This uses a (single) hi-stability master 30MHz xtal oscillator. With support from Murray (ZL1BPU), I decided to IL rather than generate an external GPS-locked 30MHz source. The only reference other than that by Uzunoglu to IL oscillator design I managed to find was in Jessop, 4th Ed, 1994 (p9.50) which stated: P1/P2 = [2Q*deltaF/F]^2 where: P1 = pwr of injected signal P2 = Oscillator (to be controlled) power Q= loaded Q of cavity (ie: xtal osc) F= oscillator frequency delta F = locking range Since Q of the oscillator is basically F(center)/BW(cavity) your equation could reduce to 2* F(center)/BW(cavity) * deltaF/F(center) = 2 * deltaF/BW(cavity) Or, the power ratio is roughly the square of how far the signal is from the 3dB point of the oscillator. That is, if the 3dB point of the closein sidebands extend 10 Hz, and your signal is 10Hz away, the injection power would have to equal the carrier power? There's an interesting article out there where a whole raft of microwave oven magnetrons were harnessed together to make a microwave weed killer, and they comment that they all tend to lock together. When it comes to coupled oscillator arrays, there's a whole lot of literature. Look for York and Pogorzelski as authors (Pogo is just down the hall from me at work.) I don't know if he's done work with coupling at a subharmonic of the output frequency. No reason why it wouldn't work. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Injection locking
You might want to look for R. Adler, A study of Locking Behavior in Oscillators Proc of IEEE, v 61, pp1380-1385, Oct 1973 Or K. Kurokawa Injection Locking of Microwave Solid State Oscillators, same issue, pp1386-1410. Those seem to be papers that get cited a lot. The coupled oscillator phased array schemes rely on the fact that the phase of the locked oscillator has a consistent relationship to how far the frequency is from the rest frequency.. if you push the rest frequency with a DC voltage (for instance), then you can get a DC voltage to phase control, which is quite convenient. If you have a whole bunch of oscillators, you can just push the ones at the edge, and the ones in the middle couple to the ones next to them and the phase has a nice linear curve across the array. I am reminded of our recent discussion on this list of an array of coupled mechanical oscillators. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Kit Scally Sent: Wednesday, February 10, 2010 3:55 PM To: time-nuts@febo.com Cc: Kit Scally Subject: [time-nuts] Injection locking Hi, As others have already noted, there's a paucity of circuits or down to earth advice on this topic - unless your poison is millimetre wave technology. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] O/T, Time Tax Pub Clocks
At first I thought O/T meant overtime (especially with a reference to Taxes and Pubs)... But then I realized you're warning us about Off Topic, but I think it's not. From a time nut standpoint, a tax on clocks would be anathema. (/tvb would be taxed into the poorhouse), at least at first glance. But even more intriguing is the possibility of convincing your local watering hole that they need an atomic accuracy clock. And perhaps we need a tax on less accurate clocks (in which case tvb has nothing to worry about). We could become the one-eyed men in the country of the blind! Legislation is needed! Inaccurate clocks are a plague on humanity. On 2/7/10 6:52 AM, David t_list_1_o...@braw.co.uk wrote: From the BBC: A pub clock dating back to the introduction of a tax on timepieces more than 200 years ago has sold at auction for £8,800. The George III Act of Parliament clock, decorated with hunting scenes, was made around 1797 and was once on the wall of a tavern. It was discovered in a house in Aberdeenshire, where it had been in the possession of a family for decades. It was sold at Shapes auction house in Edinburgh. Act of Parliament public service wall clocks, most commonly found in taverns, appeared after the introduction of a tax on all British clocks and watches in 1797. The result was many people simply stopped buying watches and clocks, and publicans tried to cash in by putting them up in their bars, hoping people would stay for a drink when they went in to check the timeSS² More at: http://news.bbc.co.uk/1/hi/scotland/north_east/8502260.stm ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ADEV vs MDEV - using sound card
On 2/6/10 6:02 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: JPL resorted to using a commercial synthesiser set for an offset of 123Hz (to minimise spurs and other artifacts) in their 100MHz N channel mixer system. And that was chosen after a lot of experimentation to find the sweet spot. Obviously, there's no special frequency, so you want to choose the one at which your gear works best. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small CPLD/FPGA for microcontroller replacement
On 2/5/10 6:14 AM, paul swed paulsw...@gmail.com wrote: On Fri, Feb 5, 2010 at 9:04 AM, Didier Juges did...@cox.net wrote: Part of the requirement is that the devices be immune (as much as practical) from SEU malfunction. I was told Atmel (or Actel?) makes flash-based small FPGAs that may fit the bill. Most SRAM devices are deemed to be excessively sensitive to SEU, even though I cannot imagine how a CPLD/FPGA could be made that does not use SRAM at all. Maybe it's a matter of quantity? A few working registers may be an acceptable risk, but the entire device operating from SRAM is not acceptable? It is somewhat relevant to time-nuttery, with respect to the recent discussion about CPLDs. The Actel parts we use for spaceflight are anti-fuse type, so the logic configuration is radiation hard. However, the actual gates and latches you instantiate are susceptible to SEU, so if you need an upset proof implementation, you have to go to TMR type schemes (many of which are automatically implemented by the design tools.. That is, they have TMR registers, etc. as part of the libraries) I think there are onchip charge pumps and such for generating internal bias voltages, and I don't know what the noise implications of them might be. But the SRAM devices aren't all that susceptible to upset on a per gate basis. The problem is that if you have a 3-6 million gate part, the probability of an upset somewhere is fairly high (in a world where we worry about 1E-12 rates). Again, you can use TMR type techniques. You can google Xilinx Upset probability or Xilinx radiation effects and get some typical numbers. There are a variety of schemes for scrubbing the configuration memory (basically always rewriting the configuration, so that a configuration upset doesn't last for very long) One needs to be careful in looking at upset rates in SRAM based parts, too... You need to distinguish between an upset in the data and an upset in the configuration memory, and they have different rates. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ADEV vs MDEV
On 2/5/10 7:59 PM, Pete Rawson peteraw...@earthlink.net wrote: Efforts are underway to develop a low cost DMTD apparatus with demonstrated stability measurements of 1E-13 in 1s. It seems that existing TI counters can reach this goal in 10s. (using MDEV estimate or 100+s. using ADEV estimate). The question is; does the MDEV tool provide an appropriate measure of stability in this time range, or is the ADEV estimate a more correct answer? ; this is NOT even close to the state-of-the-art, but can still be useful. Measurement performance of 1 sec 1E-13 10 sec 1e-14 100 sec 1e-15 1000 sec 1e-16 Would be quite impressive and useful. (and close to state of the art, and certainly better than a adhoc lashup in the lab) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] CPLDs for clock dividers
On 2/4/10 9:28 AM, Bob Camp li...@cq.nu wrote: Hi From the Altera doc's on the Max II: There's an oscillator in there to clock the flash (page 2-20). It runs at around 5 MHz. Need to turn that off. Since standby current is rated at 25ua it's something that can be done. Low standby also suggests there isn't anything else nasty sneaking around in there. If you used a non-flash based part, (e.g. On time programmable), maybe it wouldn't be as much an issue. You could check out the design with the flash part, and onece it works, you can go to a OTP part. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Martian FMT test
On 1/27/10 12:57 AM, Hal Murray hmur...@megapathdsl.net wrote: NASA is giving up on getting Spirit out of the sand trap. But it will have a new life that looks interesting to time-nuts. (frequency-nuts?) http://tinyurl.com/yzbslwz http://www.wired.com/wiredscience/2010/01/spirit-rover-probably-stuck/?utm_sou rce=feedburnerutm_medium=feedutm_campaign=Feed%3A+wired%2Findex+%28Wired%3A+ Index+3+%28Top+Stories+2%29%29 Here's a description of the telecom system on MER http://descanso.jpl.nasa.gov/DPSummary/summary.cfm?force_external=0 About halfway down the page For radio science, I suspect they'll use the low gain antenna (about 6dBi) rather than the HGA, so they don't have the position uncertainty of the HGA. The power amp puts out about +42dBm, so you don't have a lot of signal when it gets back to earth. There's link budgets and SNR, discussions of the variations in Best Lock Frequency with temperature on MER-A, etc. SDST ADEV performance is probably also in there. When you read the document MER-A = Spirit, MER-B = Opportunity. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DMTD Question
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims Sent: Monday, January 25, 2010 8:53 AM To: time-nuts@febo.com Subject: [time-nuts] DMTD Question Your board costs are WAY out of line... Are the boards 2 layer or 4 layer? You can get 2000 square inches of 2 layer boards for 12 cents/sq in + $120 setup. 4 layers are around 20 cents/sq in + $320 setup. See mylydia.com I would layout the two boards side by side and connected like they would normally be used. If you don't want to use the counter, saw it off. This would save two setup charges. So for 2 layer your cost is under $4.50 a set and under $10 for four layers. 2000 sq inches gives over 80 sets of boards. Does mylydia cost include sawing the 80 sets out of the 2000 square inches? (their website doesn't say) I think the cost that was previously cited includes all the parts on the board. And might include a variety of manufacturing incidentals that all add up, too. Some board houses automatically do the post mfr continuity tests, for instance. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Conducting Bench Top Material
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Charles P. Steinmetz Sent: Monday, January 25, 2010 10:27 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Conducting Bench Top Material Bruce wrote: Although over the years the non-conductive top has been an asset in avoiding short circuits, etc., I am concerned about static discharges when handling modern semiconductors. Would it make sense to spray the Masonite with a weak copper sulphate or similar solution so as to make the masonite slightly conductive, but not so conductive that 155 VAC connections could not safely rest upon it? Is there a better-suited material that could be used to replace the Masonite? One generally looks for static-dissipative surfaces, rather than conductive surfaces. 1 Megohm/square, for instance. The idea is to keep everything isopotential as charge drops onto things, not to rigorously establish a common voltage. I notice that many folks who have contributed on this thread use anti-static benchtops, but I have never found it necessary (and I try to keep the RH in my house under 45% -- it is generally 20% or less in the winter). I've been fooling with static-sensitive parts for 35 years and haven't lost one to static yet You haven't lost one *that you know of*. It also depends on the kinds of parts you're working with. There are some that are quite sensitive AND which don't fail outright, but just degrade performance a bit when they take a hit. It also depends on the energy behind the hit, of course. An example might be the MiniCircuits ERA-4 or ERA-5 (just because I happen to have the data sheet handy). Take a look at the later pages in the report, and you can see where the gain changes slightly as a result of 100V ESD hits (see page 6, where you can see gain dropping about 1.5 dB over 8 pulses, with about 0.1dB per hit.) As they say at the end of the report: The new amplifier ERA-4XSM shows gradual degradation in the gain and the device voltage. That fact is not so bad. Even with the multiple stress a customer would rather have gradual changes then catastrophic failure. The amplifier withstands a single 100V ESD pulse, or 3 pulses at 50V. http://www.minicircuits.com/pages/pdfs/an60028.pdf When we (JPL) do site visits to vendors, lackadaisical approaches to ESD handling are one of the common problems. For us, who are building just one or two of something that's going to be going somewhere where repair isn't an option, latent damage and gradual degradation are a big deal. It's really a habit thing that everyone has to get used to. That's why even nuts and bolts come in ESD packaging (even though they're obviously ESD immune): it gets people in the mindset of come in the area, put on the wrist strap. Back in the 70s, when ESD processes started to be used, they would have multiple categories of parts, some which needed ESD precautions (CMOS parts, DRAMs,etc.) and some which didn't (resistors, capacitors). It was found that workers would be working with something in one category, and the habits would carry over to the others, so the industry, in general, went to the everything is ESD sensitive approach. The *worst* offenders for ESD are the engineers (like those of us reading the list!), because they actually know what parts are sensitive and which aren't, and tend to take shortcuts with the non-sensitive parts. Which works, sort of, until they guess wrong, and cook something. Hey, why is the NF on this LNA 0.2 dB higher than it was yesterday? jim ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Conducting Bench Top Material
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Hawkins I learned that the human body has a capacitance of 400 pico F. Getting up from a chair could raise a couple of kilovolts. We walked on conductive rubber floors wearing conductive rubber shoes. Bench tops were conductive rubber. Nobody had thought of the wrist strap yet. If you're in and out of ESD areas, then shoes with conductive soles are easier to use than always wrist strapping. Ditto if you're working on something big where the cord for the wrist strap gets in the way. In some of our clean rooms, we have booties to go over your street shoes that have conductive coatings on them, and a conductive ribbon that you tuck into your sock to make contact. (And you go stand on a test pad to make sure, of course). I like the conductive shoes approach, it's pretty screw up proof, because you don't have to remember to plug your wrist strap in when you come to the bench, but the floor needs to be conductive, too. In those days, rubber was made conductive with carbon black. It was almost as effective as a pencil at marking things. If the anti-static material is not black, maybe it won't be a marking hazard. These days, the black bins are dissipative and not marking. The black foam is history (we all have ICs with corroded leads in the garage where the black foam turns to goo). Here at JPl, we don't use the pink bags/peanuts/stuff at all, because apparently, the coating can flake or rub off. We use plastic that has a very thin metalized layer, and I think that's pretty much industry standard now. A megohm and 400 pF has a time constant of 400 microseconds, but you do get the kilovolt spike. The wrist strap looks really good as long as your motion is the only source of static electricity. It keeps your body from ever reaching kilovolt potentials. And the megohm is important to keep you from inadvertently dying when you happen to accidentally contact the AC line. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Low temperature coefficient capacitors for DMTD
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Forbes Sent: Monday, January 25, 2010 2:22 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low temperature coefficient capacitors for DMTD Polycarbonate film production ceased about 10 years ago. Bruce They're not quite dead yet... http://www.polycarbonatecapacitors.com/ But I wouldn't use them unless forced to at gunpoint, since they are quite the boutique item these days. Seems that boutique item and time-nut might go together, if there was an actual performance advantage. Besides, think of the bragging rights from some of this stuff. It could be worse than audiophile craziness: My DMTD has capacitors made of genuine Lexan(r), not just any old polycarbonate, hand pressed to a thin film from the finest selected window glazing sheets using rollers machined from the finest steel puddled by English craftsmen in Sheffield using traditional methods. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Low temperature coefficient capacitors for DMTD
Why would JPL study obscure production details of polycarbonate film capacitors in 1990, if they fell of the market six years earlier ? We study all manner of obscure stuff here. Comes from using 20 year old parts in spacecraft that will last another 20 years. Consider Cassini.. launched back in the 90s, with equipment using heritage designs from the 80s. Those designs probably use some peculiarity of the components available, and someone had a box of the parts stashed away which was used. Every time someone proposes a new widget, they get asked in the design review: can you use any of the parts we have in bonded flight stores to save money?, and someone says Well, sure, but they're kind of old, I think we need to study whether they're any good. (there are octal tube sockets in flight stores, as I recall. Never know when you might need to refurbish a telemetry transmitter that uses them..grin)) Sounds fishy ? Anybody know what this means ? Electronic Concepts accumulated almost five hundred million hours of testing military grade Polycarbonate capacitors; and, currently meet established reliability failure rate level R. It means that they had a raft of life test fixtures with thousands of capacitors running continuously for years (perhaps under accelerated life conditions). There's a whole lot of research into figuring out failure scaling laws; e.g. does life scale with voltage to the 5.5 or the 7.5 power? Does it scale with temperature according to the Arrhenius equation? With what exponent? This is the kind of thing that spacecraft components people obsess about, because it allows them to estimate failure probabilities for something 25 years from now. I, for one, hang onto my 70s and 80s era IC databooks, because those are the parts that are flying. My grandchildren will thank me if they wind up working here. (Ohh.. I remember, grampa worked to get that radio working because it was a spare on a 1995 mission, before they used iton that outerplanets Oort cloud mission launched in 2011, and here it is at Pluto in 2040, and there's an inflight anomaly, so we better get the breadboard out of storage and see if we can fire it up) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Low temperature coefficient capacitors for DMTD
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Monday, January 25, 2010 2:48 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low temperature coefficient capacitors for DMTD In message ece7a93bd093e1439c20020fbe87c47fed2b80a...@altphyembevsp20.res.ad.j PL, Lux, Jim (337C) writes: In 1990, the conclusion of a polycarbonate film capacitor paper[1] stated, both the orientation and crystal structure of PC (polycarbonate) film affects its mechanical properties and electrical dissipation factor. The paper was a cooperative investigation by the Jet Propulsion Laboratory and Electronic Concepts' film manufacturing division, Why would JPL study obscure production details of polycarbonate film capacitors in 1990, if they fell of the market six years earlier ? Oh my.. a bit of research in Xplore finds that all the gory details were in the very section I work in at JPL (we build radios for deep space missions) Well, the original incident triggering the study was in 1978 on Voyager 2, when they weren't able to get an uplink lock to the spacecraft. The telemetry from the spacecraft indicated that the loop filter in the carrier tracking loop was having problems, most likely from leakage across the 75 uF capacitor. They figured out a workaround to estimate the best lock frequency using temperature and Doppler estimates, and Voyager continues on its happy way out of the solar system. (FWIW, the carrier tracking loop has a bandwidth of a few Hz, I think.) In fact, my office mate says that the former occupant of the chair I am sitting in as I type this spent months checking the best lock frequency of Voyager to develop that estimation approach. Frank Ott (a coworker who retired a couple years ago) did the failure analysis and figured out a way to test the capacitors and published a paper in 1985 describing it, and that paper was the basis for the 1990 Yen and Lewis paper cited in the white paper. So, JPL actually did the studying in the 80s, right around when the market for polycarbonate caps was going away. Interesting conclusions in Ott's paper: Conditions leading to a capacitor failure can occur without voltage being applied. JPL believes the Voyager in-flight failure occurred during six months of non-operation. The actual reference (from IEEE Xplore) is: Effect of structure and morphology on thermal and electrical properties of polycarbonate film capacitors Yen, S.P.S.Lewis, C.R. Jet Propulsion Lab., California Inst. of Technol., Pasadena, CA, USA; This paper appears in: Power Sources Symposium, 1990., Proceedings of the 34th International Publication Date: 25-28 June 1990 On page(s): 387 - 391 Meeting Date: 06/25/1990 - 06/28/1990 Location: Cherry Hill, NJ ISBN: 0-87942-604-7 INSPEC Accession Number:4111725 Digital Object Identifier: 10.1109/IPSS.1990.145871 Current Version Published: 2002-08-06 Abstract Research is reported to identify polycarbonate (PC) film characteristics and fabrication procedures which extend the reliable performance range of PC capacitors to 125°C without derating, and establish quality control techniques and transfer technology to US PC film manufacturers. The approach chosen to solve these problems was to develop techniques for fabricating biaxially oriented (BX) 2 μm or thinner PC film with a low dissipation factor up to 140°C; isotropic dimensional stability; high crystallinity; and high voltage breakdown strength. The PC film structure and morphology was then correlated to thermal and electrical capacitor behavior. Analytical techniques were developed to monitor film quality during capacitor fabrication, and as a result, excellent performance was demonstrated during initial capacitor testing --- And the paper's first paragraph says why JPL would do this: In March 1978, a 78 uF PC capacitor failed in a receiver tracking loop filter aboard Voyager I. This failure led to a series of investigations to duplicate the failure mode, determine the failure mechanism and establish a viable screening technique. The research was completed in 1982 [1-3]. Sporadic failures of metalized 2 micron polycarbonate (PC) film capacitors in low voltage high impedance circuits indicated lack of reliability above 100°C. Although the failure mechanism was not identified, a ramp test was implemented as a standard screening test[3], and 100°C was set as the upper temperature limit for full rated voltage use. For 125'C applications, a 50% voltage derating was recommended. You can find the paper in NASA Technical Reports Server (NTRS) at ntrs.nasa.gov... The record there says it's not copyrighted, but the electronic copy I have has the IEEE copyright notice on it. NTRS has another paper listed Review of the NASA Voyager spacecraft polycarbonate capacitor failure incident
Re: [time-nuts] Low temperature coefficient capacitors for DMTD
Finding an old 1992 MTT paper by Mysoor, et al., that describes the design of the Deep Space Transponder (DST), which is what's in Voyager.. There's a second order lowpass filter in the tracking PLL. The two time constants are 3556 seconds and 0.0556 seconds (time constant of the pole, timeconstant of the zero, respectively), the loop gain is 2.2E7 1/sec. The loop bandwidth is about 9 Hz for weak signals and 90 Hz for strong signals (50dB above threshold). There's a fair amount of information on the tradeoffs made for phase noise and Allan deviation in the papers. The Allan deviation was predicted to be 2.5E-11 for 0.01 second, 2.6E-13 for 1 second, and 2.5E-15 for 1000 seconds. (that's the incremental deviation, assuming a perfect input signal) This is, of course, an all analog transponder design. These days, we do all the loop tracking in the digital domain with a sampled signal and regenerate the carrier with an NCO. Don't have to worry about those 75 microfarad capacitors in the loop anymore (but, on the other hand, we have other things to worry about now...grin) We can probably do about an order of magnitude better on ADEV these days, with a digital radio, and maybe 2 orders of magnitude better with an all analog design. James Lux, P.E. Task Manager, SOMD Software Defined Radios Flight Communications Systems Section Jet Propulsion Laboratory 4800 Oak Grove Drive, Mail Stop 161-213 Pasadena, CA, 91109 +1(818)354-2075 phone +1(818)393-6875 fax -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Lux, Jim (337C) Sent: Monday, January 25, 2010 4:55 PM Why would JPL study obscure production details of polycarbonate film capacitors in 1990, if they fell of the market six years earlier ? Oh my.. a bit of research in Xplore finds that all the gory details were in the very section I work in at JPL (we build radios for deep space missions) Well, the original incident triggering the study was in 1978 on Voyager 2, when they weren't able to get an uplink lock to the spacecraft. The telemetry from the spacecraft indicated that the loop filter in the carrier tracking loop was having problems, most likely from leakage across the 75 uF capacitor. They figured out a workaround to estimate the best lock frequency using temperature and Doppler estimates, and Voyager continues on its happy way out of the solar system. (FWIW, the carrier tracking loop has a bandwidth of a few Hz, I think.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Test equipment / work benches...
On 1/24/10 10:43 AM, Keith Payea kpa...@bryantlabs.net wrote: Here's a couple of items from the Make Magazine site: Re-purposing IKEA furniture to hold rack mount gear: http://wiki.eth-0.nl/index.php/LackRack A workshop to dream about: http://blog.makezine.com/archive/2010/01/dream_workshop.html How many hours did that person work to make everything look good for the cameras, and what does it look like in mid project? Where I used to work (a mechanical special effects shop), we used to think about a scheme where you'd have a bench base that supported a removable bench top. The bench top had raised edges on sides and back (so stuff doesn't roll off), and a removable front edge. Then, you'd have a big motorized storage rack for the benchtops. Each project then gets it's own bench top. Work on project 1 for a few hours,then, stow it, and pull out benchtop 2 for the next project. It lets you do things like tape, fasten, or clamp parts to the bench (say, while waiting for the glue to dry or resin to cure). After all, for most projects, the vertical extent on the bench is not very much (maybe a foot or two) but the horizontal extent is great, and preferably not disturbed. What we want in that ideal shop is always lots of benches and tables so you can spread out. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Test equipment / work benches...
On 1/24/10 2:06 PM, Bob Camp li...@cq.nu wrote: Hi Complete something !! Yikes what a terrible idea. That would involve actually doing all the un-fun things that I've been putting off once the fun stuff was all done. Bob Well, even though we had a fair amount of time to tinker with ideas that might pan out, most of the work was actually for a client and had a defined delivery date (usually in a couple weeks from starting the job). And, of course, it's just like running out of room in the garage. Do you just buy a bigger garage? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rubidium Connector
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard W. Solomon Sent: Friday, January 22, 2010 9:22 AM To: time-nuts@febo.com Subject: [time-nuts] Rubidium Connector Fluke1 has an interesting Rb for sale. It has what looks like a variation of a DB-15 connector, except the center is a push-on coax connector. Anyone know where one would find this connector ? He doesn't have any. There are lots of flavors of inserts for the D-sub shell with various kinds of configurations. Coax, Triax, Twinax, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Test Equipment
What frequency ranges? If you are interested in 60MHz, then something like the TenTec TAPR VNA ($600) connects to a PC or a mac. Works as a signal generator and as a 2 port VNA. On I realize that this e-mail is somewhat off topic, however, I also believe that I will get some of the best answers from the members of this list: I have recently started to build an electronics lab, and am currently trying to acquire test and general equipment for my little basement workshop of horrors. So far, being on a limited budget, I have acquired a Tek 2465A in good working order, a Fluke 1953A counter, and my little gem (ok not quite so little) HP5345A with the 4-ghz freq converter plugin w/ opt 11 12. I'd just like to ask everyone what they would be, if they were in my shoes, attempting to acquire. Unforunately, however, I am just out of engineering school and not working with much of a budget here. I'd kill to have all the fancy gear some of you nuts have. I'd really love a DSO instead of the Tek 2465A I have. I'd kill for a good spectrum analyzer or VNA etc. Any suggestions on what I should acquire and/or suggestions for economical equipment that I should make that is a must have? I am a good DIYer when it comes to building equipment, so often I attempt to build that which I cannot afford. I appreciate everyone's' opinions in advance. Thank you. Sincerely, John Foege KB1FSX starving-engineer! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Test Equipment
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Gerhard Hoffmann Sent: Thursday, January 21, 2010 2:50 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Test Equipment Lux, Jim (337C) wrote: What frequency ranges? If you are interested in 60MHz, then something like the TenTec TAPR VNA ($600) connects to a PC or a mac. Works as a signal generator and as a 2 port VNA. Or this one: http://groups.yahoo.com/group/VNWA/ (DG8SAQ) Excellent to 500 MHz, quite usable to 1300 MHz. Does 6 or 12 term error correction, most of this VNA is software. I'm just using one to tune a 100 MHz oscillator with opened loop. :-) The only drawback is that one cannot measure compression because the absolute levels vary over f. But then it can embed / de-embed, virtual match, display the Q and equivalent circuit of a crystal from S11 measurement, L, C, time gating and and and. Outstanding.. that one is very competitive in price (using a ballpark $2/GBP conversion) to the TAPR one. I'm glad that more of these are becoming available (as assembled units, not as kits..) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4 KV Power Supply Recommendations
On 1/17/10 10:21 PM, Chuck Harris cfhar...@erols.com wrote: Ever see the spectrum of a typical microwave oven that is powered by a switching power supply? It is so broad and messed up that it will wipe out the wireless routers that share the same band. At least the old style ovens had a fairly narrow 60Hz spur somewhere around 2450MHz. -Chuck Well, yes,because the tube is basically being pulsed at 60 Hz by a half wave voltage doubler. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4 KV Power Supply Recommendations
On 1/18/10 2:15 AM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: Mark Sims wrote: A lot of the Tesla coil, etc people insulate their wires with silicone rubber tubing (available at hobby shops as fuel lines). Make sure it is silicone rubber and not PVC, etc. I have seen diode strings built up out of lots of cheap diodes (like 1000V 1N4007s). The diodes are strung together and then crammed into the silicone tubing. The ends are sealed and the tubing is then filled with mineral oil (some people use vegetable oil). power supply diode and resistor strings covered in heat shrink but don't touch as it is not good at HV. Such series strings of non avalanche rated diodes like 1N4007's without suitably proportioned parallel RC networks almost inevitably fail. Actually no. In fact, the typical recommendation these days is to not use the RC networks because they actually increase the failure probability. Today, the parts are sufficiently well matched (coming off the same spool typically) that reverse recovery time is pretty much the same. The typical problem in these strings is that one diode turns off a bit faster than the others, and so, takes more of the voltage until the other diodes turn off In a rectify from sine waves application, though, the reverse voltage doesn't rise instantaneously, so there's plenty of time for them all to turn off. This doesn't necessarily apply for flyback type power supplies, which can have fairly high dv/dt. The other thing you want to do is use a LOT of parts in series. If you're using 1000 PIV parts and you want a 5 kV diode, use 10 diodes. Where people get into trouble is when they use 5 1000 volt parts, randomly selected from the surplus bin with 70xx date codes, to build a 4800V power supply. The other thing to watch out for on Cockroft Walton type circuits is current limiting the output if there's a fault. Short the output and you discharge all those capacitors through the diodes, cooking them. You can use a series inductor if your load is constant and you don't want to foul up the (already crummy) regulation. Also, as a note, there are actual HV rectifiers from philips available widely in the surplus world. They're often 6kV PIV rating at a few hundred mA, but MUST be potted or oil immersed, because the package length is too short to run them in air at full voltage. They're designed to be seriesed or used in voltage multiplier applications, so they have soft recovery that's very consistent, and decent reverse breakdown properties, too. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4 KV Power Supply Recommendations
On 1/18/10 5:44 AM, J. L. Trantham jlt...@worldnet.att.net wrote: Is that mahogany? Has anyone ever used 'Starboard', a marine plastic? It looks like it might be a candidate for HV construction. Also 'Plexiglas'? Joe The breadboard material of choice for HV is HDPE- High Density PolyEthylene (aka the white plastic cutting board from the local discount store).. Cheap, easy to machine, good HV properties. Plexiglas (a tradename for acrylic) is brittle and tends to crack when machined, and gets worse with ozone/UV. If you want clear plastic use a polycarbonate (e.g. Lexan) that has been UV inhibited (most of the window glazing stuff is inhibited). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4 KV Power Supply Recommendations
On 1/18/10 2:10 PM, Didier Juges did...@cox.net wrote: I could not resist, so I checked my relatively expensive Sears/Kenmore microwave oven. The results are there: http://www.ko4bb.com/Test_Equipment/Microwave_oven_leakage/ In one word, dismal. Almost 1W peak power leakage at 1 foot, and almost 100MHz occupied bandwidth. I looked with a crystal detector driving a scope, and it is obvious the unit is driven from a 60Hz transformer with half wave rectification, and has no filtering whatsoever, like the first Microwave oven I have ever opened (a 20 years old model long dead). The cost of more expensive models is in the nice trim, control features, integrated vent hood, etc. They all use basically the same wiring diagram: a transformer with a lot of leakage inductance, a diode, a capacitor, and the magnetron. A higher power oven will have a bigger transformer and tube. The leakage standard is 2 mW/cm^2. A watt into your sensor indicates either a bad seal on the oven or some other measurement error. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4 KV Power Supply Recommendations
Also, consider that the RF envelope is a half wave rectified sine, so the peak/rms ratio is quite high. On 1/18/10 4:08 PM, Didier Juges did...@cox.net wrote: Looking at the detector output, it seems the 1W is a very narrow peak, probably when the magnetron starts oscillating at the beginning of each pulse. The average signal from the detector is much lower, probably by 20dB or more, so from a heating standpoint, there is not much leakage. The analyzer being on peak-hold mode with 1 MHz bandwidth, it responds to those narrow peaks. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims Sent: Monday, January 18, 2010 5:36 PM To: time-nuts@febo.com Subject: [time-nuts] 4 KV Power Supply Recommendations Dieder, That third eyeball growing out of your forehead really is quite becoming... -- The 1W peak is concerning, though, for health reasons. I guess you should keep your head far, far away. _ Hotmail: Powerful Free email with security by Microsoft. http://clk.atdmt.com/GBL/go/196390710/direct/01/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sidereal time
This is all quite interesting. 6 years ago, for the MER rovers, I cobbled together a scheme to drive off-the-shelf 24hr electric clocks off a 3325A to run on Mars time (which is slightly slower than Earth time). Same scheme can be used for sidereal time, or to make an indicator that runs at varying speeds (e.g. If you wanted to make a sophisticated tide clock or moon clock or something). A microprocessor which adds/drops pulses in the 32.768 kHz reference input is probably the cleanest way. On 1/15/10 1:27 AM, Hal Murray hmur...@megapathdsl.net wrote: If I set the 59309A to 10 Mhz external clock and dial a synthesizer up to 10.0273790, the unit should be able to keep sidereal time. Sounds good to me, but since this is time-nuts, you need a GPIB connection to the synthesizer so you can tweak it to track the details from IERS. It would be interesting to work out the details and see which is the most-significant digit that changes. Would you need to tweak the synthesizer, or are the changes off the bottom? Plan B: Do it in software. Consider a small CPU running from 10 MHz that can drive a display. If it has a connection to the outside world, then you can tell it how many ticks per sidereal second and when to start using the new value. Small LCDs are not expensive. There are some designed to fit into a disk/CD slot on PCs. SparkFun has Arduinos for $30 and LCDs for $14 and up. Some assembly required. Or get their Serial Enabled LCD for $30 which includes a PIC16F88 and figure out how to reprogram it to keep time. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sidereal time
Sure it is.. In observatories, for instance, they'll have a sidereal time display, because that's what's important. You know that Sirius crosses a N/S line at a particular sidereal time (or more correctly, isn't that the right ascension.. When the body crosses the meridian) On 1/15/10 2:07 AM, Steve Rooke sar10...@gmail.com wrote: Hi Brian, I really love this group, it appeals to the technophile inside me and it's interesting to see the answers that are given. You should have know that posting to a nuts group would mean you would get lots of highly technical responses but frequently the questions posed are not answered as things go off in a tangent. Perhaps we should have asked you how accurately bang on the sidereal second?? you wish this clock to be or perhaps you just wish it to tick over the sidereal time without some frame of reference? Sounds like an interesting idea, sorry but I cannot answer your questions conclusively but it looks sound to me. What you are doing is fitting a sidereal day into a wall clock day display by driving the clock with fast seconds so it's 24 hours is over in 23 hours 56 minutes and 4.091 seconds. If that's what you want to do, it sounds great even though I'm not sure that a sidereal day is normally presented that way. 73, Steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sidereal time
On 1/15/10 9:13 AM, J. Forster j...@quik.com wrote: Heresy: Why do you really NEED super accurate siderial time? If you are using it to point a telescope, you only need it accurate enough to get the guide stars into the field. Remember, the atmosphere refracts kinda randomly. -John = Celestial Navigation? Essentially, one determines longitude by figuring out what the difference between local solar time and sidereal time is. Now, what is super accurate? 40,000 km =24hrs, so 1 second is about 460 meters. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sidereal time
On 1/15/10 9:13 AM, J. Forster j...@quik.com wrote: Heresy: Why do you really NEED super accurate siderial time? If you are using it to point a telescope, you only need it accurate enough to get the guide stars into the field. Remember, the atmosphere refracts kinda randomly. -John What if it's a *radio* telescope? Or a DSN dish? Both of those have to track sidereal motion. At Ka-band, the 70meter dish needs pointing on the order of 1 millidegree. That's about 250 milliseconds, I guess. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
BTW, Invar has a really low tempcoefficient, but tends to random shifts in its structure, yielding to abrupt length changes. Can't have everything, I suppose... That's what my friend trying to build the 1ppm pendulum found. He found that the standard technique is to build the pendulum out of two metals with different CTE, arranged so that as the temperature changes, the center of mass of the pendulum stays the same. Imagine the long shaft of, say, 1 meter, with a CTE of 10 ppm/degree. You support the bob with a sleeve attached at the bottom of the main shaft of 30cm with a CTE of 30 ppm material (so the bob sits at 70cm from the pivot). As the temperature rises, the main shaft gets longer, but so does the sleeve, so it pushes the bob back to the proper location. (Wow, is this difficult to describe in words) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Characterization of Oscillator w/ HP5345a
On 1/11/10 4:53 PM, John Foege john.fo...@gmail.com wrote: Hello all, My concern is that I dont have a cesium reference to feed into the counter. Therefore I do not have a source that is at least an order of magnitude more stable. So what, if anything could I do? You beat your two or three references against each other. Look up three cornered hat measurement. Of course, you could succumb to the lure, and wind up like /tvb, with rooms full of oscillators and sources. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Characterization of Oscillator w/ HP5345a
On 1/11/10 6:58 PM, Brian Kirby kilodelta4foxm...@gmail.com wrote: Does your employer offer medical insurance ? Please check to see if they cover psychiatric care. Time-Nuts are more addictive than crack, plus they all have obsessive compulsive disorders. Please seek medical treatment before its two late. Next thing you know, you'll end up with several crystal oscillators, a few rubidiums, maybe a cesium, and if your willing to let you family obligations go, a Hydrogen Maser. To start, you'll want a GPSDO, so you will have a reference of some sort to UTC. Rubidiums are cheap, some at the $100 level on flea-bay, build a case, power supply and your ready to go. All is not lost, if you succumb to the addiction. It has all kinds of beneficial effects. My kids greatly envy tvb's: Dad, how come YOU aren't doing experimental proofs of general relativity with us? Other Dads do that with their kids. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
On 1/10/10 9:24 AM, J.D. Bakker j...@lartmaker.nl wrote: IHNTA, but... [...] readable by a causal bystander. ...is one of the most apropos typoes I've ever seen. Indeed... But it could be right, eh? After all, something in the past led them to look at the clock and attempt to read it? JDB. [whose customers are often pushing for acausal filters] Acausal? Or non-causal? Or reverse causal (anticausal) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Digital Clock kit - no Integrated circuits!
On 1/9/10 12:09 AM, Steve Rooke sar10...@gmail.com wrote: 2010/1/9 Tom Clifton kc0...@yahoo.com: http://transistorclock.com/ has a very interesting (though a bit expensive) kit for sale. A 10 x 11 circuit board sporting nearly 200 transistors and 600 diodes to drive six seven-segment displays. Suitable for framing... As delivered runs on 60hz but there is a note about conversion to 50hz mains. You can buy a bare board, just the components or a full kit. You must see it to believe it! Bah humbug! Stupid modern day design, it'll never be any good, you need to use valves to make real gear :-) Well, they do make dual triodes which are convenient for making those Eccles-Jordan circuits. I can't help wondering if you go do better than the 4 bit counter:4-10 decoder:10-7 decoder. Yeah, simple diode matrices in an AOI configuration are easy, but surely a bit of work (as in digging up archaic designs) could find a lower part count approach. Time to use that Karnaugh map. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Digital Clock kit - no Integrated circuits!
On 1/9/10 5:01 AM, Rex r...@sonic.net wrote: Steve Rooke wrote: Bah humbug! Stupid modern day design, it'll never be any good, you need to use valves to make real gear :-) Steve Being an Amurkan myself, by valves, I assume you are talking about a hydraulic clock. Yep. That's pretty old school. But we could step back to sundials or sand hour glasses. I guess the sundials would be the most accurate, but only during the daylight hours. Clepsydra ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Non electrical time-nuttery
OK.. So we're moving back in electrical technology But what about mechanical? Could modern technology get a substantial (order of magnitude) improvement over 19th century chronometers (either pendulum or balance wheel or whatever). I know there's some really good quartz fiber torsional spring schemes, but I think they still need electrical means to keep them moving and to read it out. So how good can one do with a mechanical, hydraulic, (or chemical, I suppose) system? Let's assume it has to have a direct readout that is human readable by a causal bystander. (this starts to sound like the 10,000 year clock or whatever it is..) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
Like a magnetically coupled escapement Sent via BlackBerry by ATT -Original Message- From: Bob Camp li...@cq.nu Date: Sat, 9 Jan 2010 12:36:11 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Subject: Re: [time-nuts] Non electrical time-nuttery Hi How about a rotary pendulum on a quartz fiber spring with some kind of trick magnets to drive it / read it out? Put the pendulum and spring inside an evacuated glass envelope to get around the vacuum pump issue. The enclosure could be pretty small. Drive the magnets with a second external clock, and feedback compensate it. Let the external clock do all the readout via a very normal gear and pointers system. The trick would be getting the feedback loop to work purely mechanically with enough gain to unload the master pendulum. Bob On Jan 9, 2010, at 2:07 PM, Lux, Jim (337C) wrote: OK.. So we're moving back in electrical technology But what about mechanical? Could modern technology get a substantial (order of magnitude) improvement over 19th century chronometers (either pendulum or balance wheel or whatever). I know there's some really good quartz fiber torsional spring schemes, but I think they still need electrical means to keep them moving and to read it out. So how good can one do with a mechanical, hydraulic, (or chemical, I suppose) system? Let's assume it has to have a direct readout that is human readable by a causal bystander. (this starts to sound like the 10,000 year clock or whatever it is..) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
One can just pump once with a mechanical pump and seal off with a flame or crimp tubulation. The pump could be driven by a waterwheel, steam or diesel engine, etc if you want to go totally non electrical. Sent via BlackBerry by ATT -Original Message- From: Bob Camp li...@cq.nu Date: Sat, 9 Jan 2010 12:12:35 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Subject: Re: [time-nuts] Non electrical time-nuttery Hi A pendulum in a vacuum clock is nothing to look down at. They are amazingly stable. Lots of machine work to build one from scratch, even if you use an off the shelf vacuum pump. Of course they are not purely mechanical. I'd hate to think about making a wind up vacuum pump If I remember correctly without the vacuum, pressure and pressure / temperature effects get to you pretty fast. Bob On Jan 9, 2010, at 2:07 PM, Lux, Jim (337C) wrote: OK.. So we're moving back in electrical technology But what about mechanical? Could modern technology get a substantial (order of magnitude) improvement over 19th century chronometers (either pendulum or balance wheel or whatever). I know there's some really good quartz fiber torsional spring schemes, but I think they still need electrical means to keep them moving and to read it out. So how good can one do with a mechanical, hydraulic, (or chemical, I suppose) system? Let's assume it has to have a direct readout that is human readable by a causal bystander. (this starts to sound like the 10,000 year clock or whatever it is..) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
On 1/9/10 3:21 PM, J. Forster j...@quik.com wrote: Maybe you could pump the pendulum optically, using a beam of light, like those glass bulb radiometers they sell that spin on a sunny window ledge. -John Hmm, and could you have a moving mirror that does the pumping? I suppose one could make a mechanical (non-electrical) sensor of a reflected beam of light using thermal means.. Like those automatic solar trackers that use propane as the working fluid. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
On 1/9/10 4:36 PM, Bob Camp li...@cq.nu wrote: Hi If you abandoned the non-elecronic side of the requirement, you could hit it with a pulsed LED and probably get phase data off of a couple of photo detectors. Crazy stuff ... Bob But that's the whole challenge... You can build an entirely mechanical clock with a performance of what? 4E-6 ADEV with a tau of 24 hrs (Harrison clock) A Shortt pendulum (whatever that is, I'll have to go look it up) is 1E-7. A friend of mine was trying to build a 1ppm pendulum clock 15 years ago, with temperature compensated weights, etc. So, can one build a 1E-8 performance clock, without electricity? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
When I was in high school (back in the 70s), I tried to set up a pendulum in the gym (Foucault style, big bob, piano wire, burn string to start) and an electronic timer to measure the change in period over 12 hours from the moon's gravitational pull. Didn't succeed, for a variety of reasons, but it was an intriguing project. For instance, at that time I didn't know that the reference oscillator in the counter I was using probably wasn't as stable over time as my pendulum was. On 1/9/10 7:01 PM, Hal Murray hmur...@megapathdsl.net wrote: Seems pretty ambitious. A reasonable goal would be measuring tides. http://www.leapsecond.com/hsn2006/ -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Non electrical time-nuttery
We have a form of fluidic amplifier here in the Los Angeles area this time of year. When the Santa Ana winds blow, they take one (sometimes two) of three possible paths. As a result, if it's windy when I leave home in the morning (in one of the paths), it won't be windy at work (in a different path), and vice versa. So it has the multistable behavior of the fluidic flipflops. I don't know if if there's an (controllable) input signal, though. On 1/9/10 9:20 PM, Max Robinson m...@maxsmusicplace.com wrote: Don't forget about fluidic amplifiers. In 1968 an older engineer at Huntsville told me to forget about transistors. They would soon be replaced by fluidics. I wonder how much longer it is going to take. Regards. Max. K 4 O D S. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] I need a clarification
2E-11 * 10E9 = (2*10)E(-11 + 9) = 20E-2 = 2E-1 = 0.2 Hz On 1/8/10 4:29 PM, Dott. Alfredo Rosati alfredoros...@alice.it wrote: I do not have much familiarity with mathematics. and errors are always behind the corner. Please someone can confirm if ± 2E-11 at 10GHz is ± 2Hz ? Is this correct or wrong ? regards alfredo i5uxj ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sparkfun
Remember that ad a couple years ago (superbowl, perhaps), with the small company starting their online presence, and the big number of orders counter. It starts clicking slowly, and everyone is jubilant: Yeah, we're going to make it; and then it starts counting faster and faster, and they get more and more crestfallen and panicky as the realize what that means. I think it was for FedEx, UPS, or something like that. On 1/7/10 8:32 AM, john.fo...@gmail.com john.fo...@gmail.com wrote: I've worked in IT for a long time, and I gurantee you, the guys in Sparkfun's IT staff are all freaking out right now!! Haha, gotta love that good ol' disaster stress in IT! John Foege Sent via BlackBerry by ATT ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sparkfun
On 1/7/10 8:32 AM, Dan Rae dan...@verizon.net wrote: F1ETB wrote: Good Advertisement for a company in Electronics... Happy New Year to everyone, Bernard I don't know Bernard. Having just wasted an hour plus of my life on it I don't think I will return there again. Dan Hmm. Let's see.. You potentially were saving $100 on something, and you spent an hour. That's $100/hr. And you truly were glued to the keyboard and screen, doing nothing else? No checking the email? Reading xkcd or slashdot? Even if you didn't successfully get an order in, you were basically making an informed bet that your time was worth less than the potential savings, since you could have aborted the transaction at any time after starting, and moved onto some other potentially more remunerative activity. Yes, it's frustrating. But a bad deal? I think not. Now, standing in line for 7 hours at some government office where there is a cellphone ban, only to be told that you have been standing in the wrong line: *That* is a waste of time, unless the value of the service is pretty darn high (e.g. Keeping you out of prison or something) Jim ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sparkfun
On 1/7/10 10:14 AM, John Miles jmi...@pop.net wrote: A couple of thoughts -- - Refusing to let people into the site at all is probably the best approach, if you find yourself completely swamped with traffic. A customer who sees 10-second ping times is likely to be even more annoyed than one who gets a 404. What they should have done, though, is served those people a static text page apologizing for the delay and inviting them to try again later... while at the same time trying to discourage them from hitting F5 over and over. - If their hosting provider isn't capable of temporarily boosting their bandwidth as needed, that's kind of lame. It should be almost impossible to slashdot any professionally-run e-commerce site these days. If nothing else, they could have rented some time on EC2 to test their connectivity beforehand. My wife deals with this sort of thing (supporting new customer facing websites) at a Fortune 500 company, and they still get bitten occasionally... You can do all the planning, arrange for fallbacks, and still stuff happens. It's tricky to serve alternate static pages, especially since you probably have a multi tier architecture to achieve persistence (after all, each HTML GET conceivably goes to a different server thread, so you need some clever way to keep track of session state for all the users.).. If you had a single threaded server, there's no way to serve an alternate page if you get backed up, and if you have a multithreaded server, it's tough to keep track of the state. A lot of folks just tough it out and hope they have enough capacity to make it through. You do a cost benefit analysis... do I spend 50K on labor to implement a bullet proof solution, or do I just fling it out there and hope for the best It's if it happens over and over at the same place, I get cranky, but this probably isn't in that category. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] are any time-nuts also random-nuts?
If I wanted random numbers that were not generated by a high quality algorithm (which can generate randomness far better than most mechanical devices), I'd go with the traditional radioactive source and a detector approach (as used by NBS to do their famous tables in the handbooks) Aware Electronics makes a little Geiger-Muller peripheral (9V DC in, pulses out) and that, in combination with a low activity source (say from United Nuclear) would work quite nicely. http://www.aw-el.com/ http://www.unitednuclear.com/ (although, with a bit of thought, you'll be able to think of an easy way to get a 1 microcurie Americium-241 source.. nice alpha emitter, about 27,000 disintegrations per second, and much longer half life than the Po210 alpha source in the antistatic brush) I've had a RM-60 for almost 20 years now, and it still works nicely. It's fun to set up a logging program and just collect data, and see how precisely it matches the theoretical Poisson distribution. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Burris Sent: Wednesday, December 23, 2009 8:07 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] are any time-nuts also random-nuts? I saw this USB connected hourglass for producing random numbers: http://home.comcast.net/%7Ehourglass/ Anyone pursuing perfect randomness in the same way this group pursues time and frequency? Maybe cryptologists. I'm tempted to build an ethernet connected variant of this. Then of course we need a distribution mechanism. How about RNDP, the Random Number Distribution Protocol? A la NTP, clients could select for the server with the most randomness :-) Scott ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Cheap Rubidium
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Wednesday, December 23, 2009 9:52 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Cheap Rubidium Hi If you can achieve = 1x10^-13 at 10,000 to 100,000 seconds, that's quite a bit better than any OCXO has a right to be doing. Yes I know that there is one in the entire universe that gets close. Even if you just do 1x10^-12 at 1,000 seconds, that's better than a whole lot of OCXO's will do at that tau. The place where the OCXO does come in is 100 seconds. Between 1 and 100 seconds you can get a number of OCXO's that will run 2x10^-12 over the entire range. You can fine a lot more that will do 1x10-12 over that range than you can find that will do 1x10^-12 at 1,000 seconds. The rubidium is struggling to get to 1x10^-11 at 1 second and may or may not get to 1x10^-12 at 100 seconds. Typical (Cassini, MGS, etc., data from Sami Asmar) UltraStableOscillator (USO) specs as used in spaceflight do about 1E-13 at tau =10 to 1000 seconds, 3E-13 at 1 second. Today, you can probably do maybe an order of magnitude better. These are state of the art oscillators in a vacuum envelope with double ovens, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Cheap Rubidium
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Ackermann N8UR Sent: Wednesday, December 23, 2009 1:30 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Cheap Rubidium Lux, Jim (337C) said the following on 12/23/2009 03:17 PM: Typical (Cassini, MGS, etc., data from Sami Asmar) UltraStableOscillator (USO) specs as used in spaceflight do about 1E-13 at tau =10 to 1000 seconds, 3E-13 at 1 second. Today, you can probably do maybe an order of magnitude better. These are state of the art oscillators in a vacuum envelope with double ovens, etc. As far as I know, the best OCXO you can get commercially today is an Oscilloquartz 8607 option 008 BVA (www.oscilloquartz.ch/file/pdf/8607.pdf), which is spec'd at 1.2x10e-13 at 1 second and 8x10e-14 from 3 to 30 seconds. TVB's page at http://www.leapsecond.com/pages/8607-drift shows it's in the 13s out to 10K seconds. The spec sheet says the aging may be 3x10e-12/day after 30 days operation (there's one option for best aging, and another for best short term stability; it's not clear whether you can get both in the same package). What they do for space applications where they care (gravity science experiments are a good example) is make a whole batch of crystals and their packages and then burn them in and look for the noise and aging properties and pick the ones they want. Each crystal will have a different turnover temperature, so that factors into the selection as well. There's a paper from Greg Weaver at APL about USO performance. It shows a daily drift rate of about 1E-11 for the GRACE USOs, and Figure 3 shows measured performance from 1 to 1000 seconds for 3 USOs. The Cassini USO has performance like John mentions (6E-14 at 10 seconds). The New Horizons USOs have drifts of 1E-11/day and ADEV1E-13 from 10-100 seconds. Lots of other interesting stuff from Greg and his colleagues in the paper as well: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA50Location=U2doc=GetTRDoc.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 60Hz mains clocking in computers
On 12/13/09 7:52 AM, Joe Gwinn joegw...@comcast.net wrote: At 1:44 AM + 12/13/09, time-nuts-requ...@febo.com wrote: Date: Sat, 12 Dec 2009 17:29:17 -0800 From: Colby Gutierrez-Kraybill co...@astro.berkeley.edu Subject: [time-nuts] 60Hz mains clocking in computers To: time-nuts@febo.com Message-ID: 3058527a-cc99-4174-be75-21dd92334...@astro.berkeley.edu Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes The CPU logic clock was not generally phase-locked to the AC power lines, instead being generated by a cheap crystal having a very large tempco. The exception to this was that video generators were (and still are) often locked to the AC line so that hum bars would not drift across the screen. Only for black and white TV before color. The frame rate of pre color TV was chosen to be 60 Hz so that hum bars wouldn't move. BUT, come color in the early 50s, and the move to 59.94 Hz (which was as close as you could get with integer division ratios from the master reference, which had something to do with solving a problem with color encoding), there's a slight difference. So that line frequency interference slowly crawls up the screen in 20 seconds. Now, most people who are not time-nuts would say that 59.94 and 60 are the same, but to us, that's a 1000 ppm difference. Woe to the person these days who tries to sync line frequency widgets (like synchronous motors) to video and film cameras (film is nominally 24fps, but if they're shooting for conversion to video, they'll sync to .999*24fps, so that the 3:2 pulldown matches the video, without having to do the dropframe thing to keep it lined up.).. I haven't done much of this in the last 15 years, but in the early 90s, there were directors of photography who used quartz locked cameras and those who didn't. Shooting with video monitors in the scene was always tricky to make sure that the vertical retrace was synced with the camera shutter; which you'd usually do by just starting the camera several times until you got the right phase or changing the camera speed slightly (by eye.. On a film camera, the viewfinder shows you the scene when the film isn't exposing. So your eye is the detector of the optical sampler.) The fancy lock boxes had a phasing knob. I got my start in the special effects business doing graphics software on modified DOS boxes that I could phase lock to the camera sync. Somewhere out in the garage I have a bunch of CGA and VGA cards with external oscillator inputs. The other strategy was to run the monitors at 24fps, and genlock the video to the camera sync output (but that was expensive, you'd only see that in feature films or long duration series..). There were some VGA cards that you could reprogram the sync rates to 24fps, too, but you had to make sure the monitor could actually lock it (and usually, you'd run a little program that started at 30fps and slowly moved it to 24, so the monitor wouldn't assume it had lost lock and try to resync) As chroma-key became cheaper and easier, a lot of times, they'd just paint the screen of the monitor blue or green, and do it in post. I'm out of that business now, but I'll bet that doing it in post is by far the most common these days. It's easy to do the projective geometry needed to warp the desired image to whatever it is in the scene (you click on the 4 corners in a key image, and the software tracks it as it moves, so you don't have to worry about camera moves) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Audio recording with time code
On 12/12/09 5:45 AM, Henry Vredegoor henry.vredeg...@gmail.com wrote: Joseph Gray schreef: My first thought was using IRIG on one of the channels. I could buy a copy of NMEATime to generate the IRIG, but then I don't have anything to decode it on playback. I was thinking the same. Are there (freeware) IRIG-B software decoder/display programs using a PC/soundcard? Henry. Google is your friend I think there's one that is part of NTP http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver6.html http://www.dolben.org/IRIG.php is another Here's one as a LabView .vi that runs on one of their FPGA cards that may provide a basis: http://zone.ni.com/devzone/cda/epd/p/id/3396 And, in a message from 2004 on this list, Dean Weiten comments The standard source package for the Network Time Protocol package, found either at http://www.ntp.org or through download with/for a LINUX distribution, has a tool in the utils directory called tg, which stands for tone generator. It can generate simple modulated IRIG-B and WWV(H) time signals on an audio card. Unfortunately, I found that it would not compile for X86 - it was apparently written for the SparcStation, I think. I've modified it to work with Open Sound System (a modern LINUX sound system), and added all kinds of IRIG options, including IEEE 1344 yes/no, daylight savings time, proper second-of-day, 1998 or 2002 format (includes years), etc. I also tweaked the WWV(H) format to make it more correct, e.g. skipping the 440 Hz tone on the 29th second, etc. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 60Hz mains clocking in computers
On 12/12/09 5:29 PM, Colby Gutierrez-Kraybill co...@astro.berkeley.edu wrote: I'm trying to get to the bottom of whether or not any computing equipment made around the advent of UNIX systems (or any time-slicing system) used the mains cycles of 60Hz as phase lock for the internal system clock. My guess is that perhaps they did not as the computing logic is DC based, but, I have memories of using an 68000 based UNIX system that I thought had its internal clock based off of the 60Hz mains... Not sure the vendor anymore. There were a variety of computers synchronized not to the mains frequency but to the horizontal retrace or vertical frame rate for video. That way, they could do things like DRAM refresh or video buffer updates in a clock synchronous way. To a certain extent, even the IBM PC was built like this, running at 4.77 MHz, divided down by 3 from a 14.3 MHz crystal (which was divided by 4 to get the 3.58 MHz color burst). If I had to guess, at the low end, boxes like the Atari 68K machines, at the high end, 3Rivers PERQ (but that one sticks as using 2901 bitslice...) Anything intended to generate video for integration with other video streams would greatly benefit from being able to be synchronized to the NTSC 59.95 Hz frame rate, and if the video memory is the same as the system ram, then running the CPU clock at an exact multiple makes designing the memory access arbiters easier (they can be synchronous), so what you really want is the pixel rate being a multiple of 59.95 and the CPU clock being a multiple of the pixel rate, so that wait state generation is easy (or you can do transparent/hidden access to RAM during a time when you KNOW the CPU won't be looking at it). More than one system used the video access to do DRAM refresh, too. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Audio recording with time code
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Joseph Gray Sent: Friday, December 11, 2009 10:30 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Audio recording with time code Does anyone know of an inexpensive or free program that will record audio on one channel and time stamp it on the second channel (assuming stereo) A VOX capability is also needed. A Windows program is preferred, but I will consider a Linux one. The other side of this is on playback, I'd need to have a visual indication of the timestamps. An all-in-one program would be ideal. Joe Gray KA5ZEC Could you use one of the sound card audio timecode generating programs and patch it to the second input? Most recording programs have a way to mix things, and there's programs that create virtual audio cables, too. http://software.muzychenko.net/eng/vac.html (note that the demo has a voice nag-ware periodically) Jack also provides a similar capability. You might look at DL4YFH's spectrum lab program too (I use it all the time for a variety of things.. I haven't looked at timecodes, but it wouldn't surprise me if he has a way to generate timestamped files, using the PC clock) ARGO does timestamping in some manner (http://www.weaksignals.com/) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Audio recording with time code
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert Atkinson Sent: Friday, December 11, 2009 10:49 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Audio recording with time code Hi Joe, Do you wnat to record on the PC or some other medium/device? What accuracy / resolution do you need? A standard for recording time on audio is IRIG timecode, most common is IRIG B (google it). This is an amplitude modulated 1kHz tone. NMEAtime is a program that will generate it with a PC sound card. Robert G8RPI. There's also SMPTE LTC (Longitudinal Time Code) which is aimed at the audio/visual production business. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Chooses for a desktop/server NTP external 1PPS reference
(btw is there such a thing as a desktop rubidium atomic clock with 1 PPS?) Stanford Research prs10 (List $1495) is a building block FS725 is a fancier version in a box with power supply, 1pps in and out, 5 and 10 MHz etc, RS232 interface, etc. List about $2500. http://www.thinksrs.com/products/FS725.htm ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FE-30 OCXO
On 12/4/09 7:31 PM, Bob Camp li...@cq.nu wrote: Hi A little more background on FEI. For quite a while they were a major supplier to the high end of the military and space end of the oscillator business. A lot of their work was on classified projects. They branched out into the atomic clock business and also into the sub system business. Nothing they did was ever going to sell on the cheap. Eventually this got them in hot water with the US government. The settlement of the case effectively barred them from competing on DOD projects. As a result they turned more to the telecom and commercial end of the business. FEI is also a supplier of oscillators for deep space transponders and space instruments. I think that the Seawinds instrument on QuikScat used a FEI 28MHz STALO (even though launched in 1999, it was a modified version of GFO ( Geosat Follow On), which I believe was an 80s design) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Power level reference
On 12/2/09 12:01 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message c793a5fe0912012031k12893065w2682c6e74c920...@mail.gmail.com, Josep h Gray writes: I also found lots of Google hits for the AD8307. Within its limitations, this chip seems to be very popular. Please notice that most of these chips are intended for AGC purposes for transmitters, they very seldom have a frequency-flatness spec worth anything The 8307 and it's ilk are actually quite flat over frequency. Real broadband amplifiers in the log chain. Is it 0.1dB flat? I don't think so, and in an case, layout might give you more ripple than that. But certainly better than 0.5dB practically. The 8307 datasheet says 0.3dB typical for the middle 80dB range for frequencies less than 100MHz, and I'd believe that, based on the ones I've seen hooked up. That's about 1/10th of the -3dB frequency for the logamps in the chain, so they're quite flat. Specs on a logamp are tricky to evaluate against a square law or linear detector because it's tough to know if it's the log function or the basic detection that's at issue. For the thermistor mount, you're lucky to get 30dB dynamic range AND the accuracy will be worse at the bottom end, because a good portion of the measurement uncertainty is fixed, not a fraction of the input. For a diode detector, the newer meters know the cal curve of the diode, so they're not depending on the squarelaw characteristic, and you get maybe 50dB dynamic range, but again, the accuracy at the low end is worse than the high end. I wonder (just haven't looked til now) what they're using inside those USB power heads (e.g. MiniCircuits)... Is it a AD8307 type widget or a diode? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Power level reference
There was a special issue of IEEE proceedings about 30 years ago on just this subject. I'll see if I can find the date (it's on my desk at work) Basically, you always wind up going back to some sort of calorimetric standard: some sort of load which you measure the temperature rise of, and that you can calibrate the mass/thermal properties of by some sort of DC replacement (since it's straightforward to accurately measure voltage and current). Be aware that this is only part of the game. There's also the whole mismatch issue to deal with, and for microwave frequencies, the mismatch uncertainty often dominates over the uncertainty of the power reading. You can also read up on the NIST Type IV power meter. On 12/1/09 12:17 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message c793a5fe0911302041p1bcde3e0p13deca7efe9c9...@mail.gmail.com, Josep h Gray writes: We all have our various highly accurate frequency and perhaps time references. Is there a relatively simple and inexpensive method of making an accurate RF power level reference? If so, then what do we calibrate it with, not already having such an accurate reference? I investigated that some time ago, in relation to calibrating the HP3458A. The way you do it, is with a thermal converter. I've been playing around to see if instead of a thermocouple it would be possible to do the sensing by infrared light, and it looks possible but I have not spent enough time to nail it usably yet. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] LORAN-C demise
On 11/29/09 11:40 AM, Mark Spencer mspencer12...@yahoo.ca wrote: Any thoughts on how complex a receiver would need to be to produce a 1 pps signal that was locked to the carrier frequency it was receiving ? Lot#39;s of comercial transmitting equipment is designed to use an external frequency standard and if a transmitter at a high altitude site was locked to a cesium source it could serve a typical metroplitan area. Locking an existing transmiiter to a cesium standard would not require any special signals or wave forms to be transmitted. To be usefull the receiver would need to produce a standard 1 pps output. Stanley Reynolds wrote: How about the Volunteer Association of GPS Backup for Timing, VAGBT ? Propose of the group is to provide backup distribution of timing information for GPS users, via armature radio and cesium clocks. To develop many local transmit stations as possible and low cost receivers with both extended holdover and comparison to GPS to measure backup accuracy. Many low power transmitters would be required as the cost of continuous operation would be lower for each station, and the identification of less accurate stations possible if several in each location was avabile. And how is this is different from time stations like WWV or WWVB? They're driven by cesium clocks (or an ensemble of clocks). The atmospheric propagation uncertainty means that the received instantaneous frequency might be off by 1E-7 or so (for HF WWV, at least), but I would imagine that averaged over a long time, it's quite a bit better (one NIST doc says 1E-9), but apparently it's tough to do straight averaging. The station clocks at WWV is is good to something like 1E-13 (adev of 1E-13 at tau of 10,000 seconds, down to about 2E-13 at tau of 1E6 seconds) WWVB at 60kHz is different.. It's from the same master clock, but the NIST doc says that received phase is stable to 1E-8 at tau of 2 seconds, down to 1E-9 at a tau of 1000 seconds, with a WWVB disciplined oscillator getting down to around 1E-12 for averaging over a day (which NIST says is about 1 order of mag worse than a GPS disciplined oscillator) Of course http://tf.nist.gov/general/pdf/1969.pdf says they use common view GPS to sync the WWV transmitter to the clocks in Boulder. It doesn't use GPS for time, just as a source visible to both at the same time) The same document claims that 0.1 millisecond absolute time uncertainty should be achievable with the received signals of WWV/WWVH and perhaps 1 microsecond for WWVB. One can propose, say, VHF or UHF signals radiated from a high location which would potentially have better instantaneous frequency stability (because the propagation is more stable), but at some point, you're still going to have to deal with things like SNR and propagation. Granted a lot of those issues are solved in some sense (e.g. You could set up a GPS pseudolite, like they do for approach/landing navigation experiments) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Spread Spectrum Spam!
Some spacecraft have a requirement that all the PWM supplies by synchronizable to an external source. The idea is that at least the spur is in a constant location, rather than wandering around (PWM natural switching rates not being the most stable in the world) On 11/27/09 12:40 PM, Robert Atkinson robert8...@yahoo.co.uk wrote: Interestingly some amateur radio 13.8V switch mode supplies have a QRM (interference) reduction control. This shifts the PWM frequency slightly so you an shift the noise off of the signal you are listening too! Complete fudge. In Europe the CE EMC tests use Quasi-peak detectors and slow scan rates that respond less to spred clocks. The spreading can be turned off in the BIOS on most machines if needed. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NMEA Time
You aren't going to get nanosecond accuracy out of a ntp server running over an ethernet[1]. On the other hand, sub-ms isn't hard with a good OS and/or good software. It's fairly easy to get a reasonable sanity check on a (s)ntp server. Just setup a known good ntp system and have it monitor the DUT. The reference implementation for ntp (http://www.ntp.org/) has lots of support for collecting data. The key step in making a PC keep good time is tweaking the clock frequency. This is the software equivalent of the EFC on an oscillator. ntpd calls it drift. You can use it as a thermometer. I don't think the oscillator quality in the typical PC is good enough to ever get nanoseconds, even with tons of tweaks and temperature compensation, etc. The short term variability/phase noise is too high. Microseconds, I think you could do. -- 1) There is a group working on that level of accuracy. It takes special hardware that can put a time-stamp on a packet as it leaves or arrives. http://en.wikipedia.org/wiki/Precision_Time_Protocol More than just a casual group. You can buy IEEE 1588 products from, among others, Symmetricom. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rubidium standard / MTBF
On 11/19/09 4:56 AM, Bob Camp li...@cq.nu wrote: Hi The one that I find the most shocking is the very major internet hardware company that considers 5 years of continuos use to be the goal. The logic - we want them to swap out the gear regularly That's actually reasonable.. Moore's law is always advancing, performance is improving, and regular swaps avoid needing to support old versions for long times. A pretty simple financial analysis shows what the optimum plan would be, and I'm sure that's what the MIHC does. We face the opposite issue at JPL.. Supporting 20 year old hardware in space (which is pretty benign) or more to the point some ground testbed that replicates it. The flight hardware or prototype probably isn't the problem, it's the Apple II computer hooked up to it in the testbed that gives you diagnostic information, or is used to generate the software builds using a program that runs on the Microsoft BASIC card installed in that Apple. (or Rocky Mountain Basic on that HP calculator, or...) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] funky frequency
More likely it multiplies up to something useful. For instance, for deep space communications, older radios multiplied up something around 5 MHz to get the 2.x GHz or 8.X GHz transmit frequencies.. 9.5625 MHz * 880 gives 8415 MHz, which is in the middle of the Deep Space space to earth band. The corresponding earth to space frequency would be 749/880 times that. Similarly in the 2 GHz band, the ratio is 221/240. The entire system is based on the crystal frequency chosen for your channel and stuff is divided up and down. Until very recently, you got an allocation for your mission (many years in advance) and you'd order your crystals, wait a couple years for them to be delivered, then install them in your radio and tune it up. If your mission happened to use a spare radio from a previous mission, you'd hope you could use the same channel so you didn't have to get a new crystal. More at deepspace.jpl.nasa.gov/dsndocs/810-005/201/201A.pdf Not that your OCXO was used for that, but there are a remarkable number of fixed frequency systems around with oddball frequencies. I'll bet there's a lot of terrestrial microwave systems that multiplied a ovenized oscillator up to the frequency of use, and since they're on fixed allocated channels, there's no particular reason why one frequency is any better than another... They're all custom. On 11/19/09 10:48 AM, Don Latham d...@montana.com wrote: I just found in my dusty junk, a couple of ovenized frequency sources at 5.199155 MHz, part# EROS-750-MA111 Dunno why I got these. Is this a magic frequency? It does not seem to divide down to a baudrate... Don ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] MTBF (was Rubidium standard)
Yeah, but in the one-off spaceflight world, MTBF calculations don't get used much, except perhaps to compare designs. (e.g. A design with an MTBF of 200khrs is probably better than one with 2000 hrs) The problem is that it's a statistical sort of life measure: out of 1000 units with an MTBF of 1000 hours, you can expect 500 to still be working at 1000 hours. It doesn't say much about whether your ONE box will be working at 10 hours, which is typically what you're worried about. What they do is buy good parts, use really skilled people and consistent processes, check everything 20 times (and how many times did we look at each solder joint), test the bejeebers out of the box at many stages, put a couple thousand hours on to get past infant mortality issues, and hope for the best. This is a somewhat conservative approach, which is why Mars rovers with a requirement for 90 day life are still going some 6 years later. On 11/18/09 3:01 PM, saidj...@aol.com saidj...@aol.com wrote: Hi Alan, I am reading a book about the Apollo computer, they bet their life on it not failing (everything related to spacecraft maneuvering went through the computer, there were no mechanical or other backups whatsoever). They only had a single computer per spacecraft! The book states that based on the entire Apollo program, they later estimated the units MTBF to be in excess of 50,000 hours (which is actually not a lot compared to what typical GPSDO's can achieve today). A single transistor, ROM bit, solder-joint, or resistor failure could have killed them. Scary considering they went for 2 week+ missions.. bye, Said In a message dated 11/18/2009 14:38:57 Pacific Standard Time, alan.me...@btinternet.com writes: Sorry Mike , unless, as someone else said, the figures are derived from field failures over at least a good porton of the expected like the MTBF tells you absolutely nothing!! The statistics used on the usual 1000hour test will only tell you the probability of failure in the first 1000hours of use!! It cannot tell you anything mathematically about the extrapolated lifethis has become another urban myth. If it works it is more by luck that by mathematical probability. Alan G3NYK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
A *much* more effective and cheap strategy is a repeater jammer.. Receive the signal and retransmit it: two antennas and an amplifier. The victim sees the delayed retransmitted signal at a higher level than the direct one. It's sort of like creating fake multipath interference. No need for PN generators, oscillators, etc. Granted, a smart receiver that *understands* the relationship between SV to user geometry and doppler can beat it (because the carrier phase and PN phase of the repeated signal won't be consistent with the geometry), but the run of the mill PN tracking loop probably won't. Most inexpensive receivers use a single bit sampler, so a suitable CW tone could also probably jam it effectively, but might require some knowledge of the victim receiver to pick an appropriate frequency (i.e. You'd need to know the sampling rate.) On 11/15/09 4:39 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Chuck Harris wrote: Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. The schematic out there is a PN source feeding an OCXO and then amplified. Crystal loop to keep fairly centered. More or less the same as personalized phone jammers do. Very simple design. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On 11/14/09 3:28 PM, J. Forster j...@quik.com wrote: Somehow, I think they will keep GPS running whatever the cost. There is a huge civilian constituency (everybody who cannot or is too lazy to read a map) and relies on GPS to guide their Lexus to the nearest Starbucks. Also, the military needs it to guide and target munitions. The initial Afgahnistan victories over the Taliban would have been impossible without GPS and the Special Forces teams. The folly of the decision will likely not become apparent until there is a major tragedy of some kind. Frankly, I doubt that $190 M would buy a single GPS bird and launch today. I'll bet $190M would buy the bird and launch. The typical LEO science satellite runs about $50M to put into orbit (i.e. Deliver ready to integrate satellite to whereever, and $50M later, it's in orbit). The MEO orbit for GPS might be a bit more expensive, but not hugely. Launching several hundred kilos to Mars or the Moon runs about $100M. If you're building multiple satellites that are truly identical, then a recurring cost of $50M each is totally believable. Again, for context, the typical small earth orbiting science satellite typically has a total project budget (exclusive of launch) of around $100M, and that's to do multiple instruments, get the bus, integrate, etc.. A larger Discovery class (e.g. Messenger, Dawn, Deep Impact, Genesis, Kepler) mission would be in the $350-400M range. New Frontiers class (New Horizons to Pluto, Juno to Jupiter) are in the $750M range (650 for spacecraft, 100 for launch), Flagship are the multi-billion dollar (e.g. Cassini) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] LORAN C shutdown
On 11/9/09 2:43 PM, paul swed paulsw...@gmail.com wrote: I believe sextant On Mon, Nov 9, 2009 at 5:25 PM, Eric Garner garn...@gmail.com wrote: So what are ships/planes supposed to if/when satellite navigation becomes unreliable or unavailable ? On Mon, Nov 9, 2009 at 2:14 PM, J. Forster j...@quik.com wrote: The Congress is UTTERLY CLUELESS. It's supposed to shut down Jan 4, 2010. --- What do they when the satellite stops? The same thing they do when Loran stops... celnav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Calculating frequency differences using Lissajou figures
You got it exactly. The relative phase between the two signals (as displayed by the Lissajous) rotates one cycle in 182 seconds.. E.g. 1/182 Hz difference. On 11/7/09 11:34 AM, Mark Amos mark.a...@toast.net wrote: Time-Nuts, I recently fired up an Efratum LPRO and have been watching the slowly rotating Lissajou figure produced when comparing it's output with that of a GPSDO on a scope. It's a beautiful thing (the weather is too cool to watch paint dry...) I thought the period of rotation of the Lissajou figure could be used to determine the frequency difference of the two oscillators, but the math escapes me. Is it as simple as calculating the inverse of the period of the rotation through 360 degrees? In this case the period between in-phase and in-phase is 182 seconds yielding a rotation frequency of 5.5 mHz. So, is 5.5 mHz the frequency difference between the two 10 MHz oscillators? Or am I missing something obvious? Thanks, in advance, Mark ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Calculating frequency differences using Lissajou figures
On 11/7/09 12:29 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: Tom Va 100 ns / 182 s = 5.495e-10 on November 7 100 ns / 188 s = 5.319e-10 on December 7 So your frequency drift in this example is 1.7e-11 / month. /tvb Not quite, you need to take the sign of the frequency difference into account. ie in your example above the sign of the error measured on November 7 has to be identical to the sign of the error measured on December 7 for your calculation to be correct. But the sign of the difference would be obvious from the rotation direction of the Lissajous. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Spectrum Analyzer
On 10/31/09 5:26 AM, John Ackermann N8UR j...@febo.com wrote: The HP8569 is a good moderate-price choice that goes up to 18GHz. It's new enough to have digital display, so you can do trace math like normalization, and dump plots via GPIB. However, you cannot set commands via GPIB. John Brent Gordon said the following on 10/30/2009 11:06 PM: I'm thinking of buying a spectrum analyzer and would like to know what Time Nuts recommend. My requirements are fairly simple: 3GHz Max frequency or higher Either GPIB or Ethernet interface for control and data capture Not much larger than an average desktop computer. Portable is nice but not necessary. Preferably under $3000. I thought about building Scotty's Spectrum Analyzer or Poor Man's Spectrum Analyzer, but decided I would rather buy one then build one. I have an HP 141T but I am looking for something more modern. One of my uses will be looking at C and Ku band satellite signals (down converted to 950-2050 MHz). I'll also be using it to look at various RF data links from 433 MHz to 2.4 GHz. Since you're thinking about building something, how about somewhere in between a piece of lab gear and total homebrew. The PC controlled receivers like the Icom PCR1000 work pretty well as a spectrum analyzer and tune DC to 1 GHz-ish. So a good LO and a mixer in front of this might be a way to go. Yeah, you won't get the whole 3 GHz in one span. For smaller resolution BW than the narrowest filter in the PCR1000, you can run the audio output with the receiver in SSB mode into a spectrogram program. Instead of the PCR1000, you could use one of the SDR widgets out now (like a softrock), but that's going to be a LOT more homebrew. The LO for mixing down from microwaves could be done a bunch of ways. There's PLL eval boards which have a USB interface, for instance. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast freq. synthesis schemes
On 10/14/09 6:08 PM, John Miles jmi...@pop.net wrote: Ooohh.. Sampling Phase Detectors or Harmonic Mixers.. The problem is that you have to hit them with a lot of power on the reference port (+20dBm wouldn't be unusual) Depending on your application, making that much LO power that is suitably quiet is a challenge. Presumably, though, you're not DC power limited, so that helps. Yes, if the goal is to breadboard something at home the constraints are looser in some ways and worse in others. The Hittite parts are all QFNs that are annoying at best to dead-bug. Ah.. But they come on eval boards with connectorsgrin.. (cost a bit more too, as I recall The LO side isn't typically a problem in a sampler loop with a fixed drive frequency. Mini-Circuits has a useful monolithic amplifier chip, the HELA-10, that yields 1 watt from HF to 1 GHz with a 3.5-dB NF. You can feed it with a typical +15 dBm OCXO and put ~+25 dBm into your sampler for $20, and they even throw in the baluns. Or for $75 they will sell you a gold-plated, connectorized and enclosed eval board. One of the real unheralded bargains out there, as far as broadband driver amps are concerned. That *is* handy to know.. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast freq. synthesis schemes
On 10/15/09 5:56 AM, Luis Cupido cup...@mail.ua.pt wrote: Hi Bert, Thanks for the input. briefly; -Phase noise is not too important -It is to make just a few (and cost is not a major issue) The suggestions using prescalers or any other high speed digital chips may bring simplicity while compared with the design using multiple loops and harmonic mixers and samplers that is something I had in mind when I place the question out. I was wondering if recent technology would make possible to have a simpler approach. I like your first suggestion but I fear the spurious... I have no clue how bad it will be, but I guess I can only be sure if I make a prototype of that. The second one I must check how small would be the step... 1 MHz would be enough for a start. The spurs might not be as bad as you think... The newer crop of DDS include some forms of error cancellation for close in spur reduction, so the in the loop bandwidth part is cleaner. Also, maybe you can use clever choice of DDS clock rate to make sure that you only need nice phase increments that evenly divide into the lookup table length. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] frequency sources
On 10/15/09 7:20 PM, Don Latham d...@montana.com wrote: Some list members indicated a need for a well-controlled easily set frequency source. Another list I get has to do with software defined radio (softrock40). A member of that list mentioned a Maxim chip, the DS1077 oscillator/divider. The chip plus breakout board is close to ten bucks from Sparkfun. This chip will put out two frequencies and is I2C programmable. Over its temperature range, it is goodto +- 1.4% of its fundamental frequency. We have some similar parts here at work, and the output waveform may not be very symmetric or even consistent from cycle to cycle. It's sort of like the problems with clock oscillators designed to reduce EMI by dithering the period to spread the spurs... Even running it into a divide by 2 (which would make a symmetric output) doesn't necessarily work if it's using some sort of funky divider scheme where only the average period meets the requirement. I'm not familiar with that particular part, but it's something to be aware of. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Getting GPIB to work on HP5382B Universal counter
On 10/14/09 5:46 AM, Mike Naruta AA8K a...@comcast.net wrote: The standard I used in my department was that when anyone changed code, they commented out the original code and then entered their new code with a date and explanation of the change. That way you have the what and why the previous developer originally thought he was doing and what, when, and why you changed it. These days, with versioning source code repositories (like SVN) and code browsers that understand the repository, it's a simple matter to get a diff, highlighted in color even. The commit comment to the repo should say who why what, etc. Now.. If you check out, spend 6 months tinkering in 500 modules, and then do the commit, you're probably going to regret it. But if you do small changes and commits, it works pretty well. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast freq. synthesis schemes
On 10/14/09 12:25 PM, Luis Cupido cup...@mail.ua.pt wrote: Hi, I'm looking for the schemes used on the frequency synthesizers that change frequency in few microseconds time (or less) at microwaves lets say circa 12-18Ghz) Obviously with some resolution (let's say 100Khz step or in that order)(otherwise it would be a trivial exercise in the BW of the PLL loop filter) Does anyone know of some paper or tech notes from some instrument or modules that show block diagrams of such? Look at how the PTS synthesizers work.. A series of decade modules, lots of adding, mixing, filtering. Off the shelf they do sub microseconds. A DDS feeding a multiplier (not a PLL mult, but a step recovery diode or similar) also will have very fast switch time, and might even be phase continuous. Your challenge with this approach is going to be spurs. I have many info on mw synthesizers but all fall into microwave radio style of things with much higher resolution (khz and less) and much longer switching times (millisencods or more). Info on fast stuff I can't really find. That's partly because fast frequency hoppers and frequency agile radars are export controlled, and that's one of the applications of a fast switching synthesizer. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast freq. synthesis schemes
Behalf Of Luis Cupido Sent: Wednesday, October 14, 2009 3:25 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] fast freq. synthesis schemes Hi, I'm looking for the schemes used on the frequency synthesizers that change frequency in few microseconds time (or less) at microwaves lets say circa 12-18Ghz) Obviously with some resolution (let's say 100Khz step or in that order)(otherwise it would be a trivial exercise in the BW of the PLL loop filter) What range does it need to tune over? The whole 12-18, or some smaller section? You could use a fixed oscillator, multiply it up, and then mix the output of a DDS, perhaps also multiplied. 1 GHz works nice as a clock to a DDS, and as a basis for the fixed part. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast freq. synthesis schemes
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles Sent: Wednesday, October 14, 2009 4:44 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] fast freq. synthesis schemes Pretuning is the right strategy, but for microsecond agility, YIGs may be the wrong choice due to their main-coil inductance. If I were building an agile 12-18 GHz synthesizer I'd try a heterodyne scheme with varactor-tuned oscillators and a fixed (or very coarsely tuned) YIG or DRO. Either way, you would probably use a sampler, such as the parts in the Aeroflex/Metelics catalog, to construct the outermost PLL. Suitable counter and PFD chips exist as well (Hittite etc.) but samplers are cheaper and easier to use if you don't mind designing the IF circuitry for them. Ooohh.. Sampling Phase Detectors or Harmonic Mixers.. The problem is that you have to hit them with a lot of power on the reference port (+20dBm wouldn't be unusual) Depending on your application, making that much LO power that is suitably quiet is a challenge. Presumably, though, you're not DC power limited, so that helps. Getting a PLL with simple single integer N is pretty easy with the Hittite parts, especially if you can tolerate N that is a multiple of 4 or 8. There's a paper out there by S.K.Smith, et al., that describes a breadboard PLL we did at 8GHz, where we drove the reference input with the output of a DDS mixed with a fixed signal. http://tmo.jpl.nasa.gov/progress_report/42-166/166A.pdf take a look at Figure 6 and 7 However, that won't change in less than a microsecond (the loop bandwidth is too narrow).. you could widen up the loop bandwidth, but the reference source would need to be quieter (not a challenge.. we didn't take any special efforts to make our DDS quiet, etc.) The earlier paper by Cook, et al., http://tmo.jpl.nasa.gov/progress_report/42-156/156C.pdf shows a more traditional SPD DRO PLL, and gives some performance analysis of the loop. Just as in the Smith paper, tuning speed wasn't a big deal for us, but the theory is there to generalize it. I would use a DDS, but only for fine tuning in a summing loop. E.g., use a DAC to pretune the varactor or YTO to within 50 or so MHz, feed the sampler LO port with a clean 100 MHz crystal, then close the loop by comparing the sampler IF to the DDS-generated offset signal. This is a nice technique. The trick is in making sure you lock to the right comb and the right side.. But the external DAC can help with that. That way the PN is dominated by the lower N factor assocaited with the 100 MHz comb, and the resolution is determined by the DDS. Yes. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] unités conventions internationa les
On 10/12/09 2:25 AM, AL1 alain2.bouc...@wanadoo.fr wrote: HI all timenuts lovers, i think it is not a question in our hobby : we have to use the international unities system (SI) as result fron the international conventions. I warm recommand to read that: http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf it is on the site of Bureau International des poids et mesures (BIPM), and is of first interest. Naturally in our life we can do as we think (...!?), but in any scientific domain it is no question of approximative! remember the lost of Mars orbiter due at the misusing of unities! Indeed.. Possibly, though, it was the (almost) universal use of SI that led to the problem with the data. It probably never occurred to the people at JPL that someone would use anything other than SI units, and so they didn't check. The numbers, in either units set (pounds or Newtons) were very small compared to other things going on, so the discrepancy between observations (noisy) and the model outputs (also noisy) as the result of a factor of 5 error in magnitude to the inputs to the modeling code was attributed to other things. (I work at JPL, but I haven't talked to the navigators for the ill-fated '98 missions, so I don't know.. Just speculating here) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DAC resistors
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Neville Michie Sent: Tuesday, October 06, 2009 3:19 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] DAC resistors Hi, I am constructing a phase meter to monitor the phase creep of clocks. It consists of a BCD counter counting say microseconds that has its count strobed into a latch by a pulse from the clock. The Latch drives a DAC which drives a pen recorder and an analogue data logger. Now I am familiar with R - 2R networks, and that method is used on each decade but the resistors that combine the decades in a 10:1 ratio are the problem. I have an approximate value, and I will probably have to trim them to eliminate digital errors later. But I can not find a reference anywhere to how to calculate the correct resistors or even a working example except for an old Analog Devices data sheet which seems to use a different structure, by reducing the supply voltage of each decade. Do you have a summing amplifier? What about resistive dividers in a 1:10:100 ratio.. Say your r/2r network is designed to dump into a 1K ohm load to ground? If you replace the 1K with 1K in parallel with 10K, the current through the 10K will be 1/10th that into the 1K (actually you need to pick 1.1K and 11K or whatever works out to give you 1K in parallel). The 1K goes to ground, the 10K goes into the current summing junction of your opamp (which is at virtual ground) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna and lightning
On 10/4/09 6:00 AM, Brooke Clarke bro...@pacific.net wrote: Hi Kevin: I agree with all you have said regarding how the wiring should be to minimize currents in equipment, but . . . It is possible to greatly lower the possibility of lightening striking some location. It's done by using what amounts to bottle brushes made of metal that are about 3 in diameter and a few feet long. You place these below and around the GPS antenna and make a good connection to ground. They bleed ions from the earth into the air forming clouds (pine trees do a similar thing). This method has been thoroughly discredited in numerous peer-reviewed articles. It was also the subject of litigation against IEEE by a manufacturer of such devices (as I recall, claiming that by publishing the papers, it was interfering with their business.. Etc.) One mfr uses as used by NASA in their literature, neglecting to mention that NASA bought a whole raft of such products to do effectiveness testing, and the report of that testing found that they have no effect or actually increase the probability of strikes. There's a great picture of a lightning strike directly to the device on the side of a tower at Cape Canaveral. Google for Abdul Mousa and Lightning for the early parts of the story.. Then, there's the paper from Moore at the Langmuir Lab in New Mexico (where they study lightning effects) Charge Transfer System is Wishful Thinking, not Science.. Or the paper by Martin Uman and Vadimir Rakov (who literally wrote the book on Lightning, more than once) in AMS Journal Dec 2002 A Critical Review of Nonconventional Approaches to Lightning Protection ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS from a window seat
On 10/4/09 11:08 AM, David I. Emery d...@dieconsulting.com wrote: On Sun, Oct 04, 2009 at 09:14:29AM +, Robert Atkinson wrote: Hi, This is correct. There was also an issue with harmonics from the local oscillator in the aircraft's own VHF nav/comm receivers blocking the GPS. The answer is a 1575MHz notch filter, e.g. http://www.edmo.com/index.php?module=productsfunc=displayprod_id=18006 I have not (not being involved in avionics professionally) heard of any problems with GPS receivers causing interference to other GPS receivers or other avionics ... I would be interested in your comments on whether you know of any such issues and what the mechanisms are. Most of the receiver designs I'm familiar with use some sort of single bit sampler running at some tens of MHz. If the sample clock happens to be say, 1/3 of a bad frequency (e.g. Around 40 MHz, so the third harmonic is 120 MHz, in the middle of the aviation VHF band), you might have an issue with the clock coupling back out the antenna port. Fortunately, most receivers ALSO have some sort of filtering (because the receiver would be sensing the self same 120 MHz aviation signals, etc.) which should suppress the harmonics. The L band bandpass filter would let a very high harmonic out, but I'll bet it wouldn't interfere with other GPS receivers. Then, there's all the usual radiation through the case problems, but I suspect that GPS receivers are no where near as bad an offender as a laptop or PDA or iPod or or or or.. I have read that there have been studies with a spectrum analyzer system on planes that have shown that compliance with the no radiating device rules and electronics off during takeoff and landing is far less than 100% though I certainly would not personally deliberately violate the law whether or not the probability of it causing a problem is significant. Apparently one or two cellphones can be seen registering with cell systems during takeoff and landing on many flights - probably most of them unintentionally left on. There was an article in IEEE Spectrum about this. A Agilent portable spectrum analyzer with battery power and a data logger in the overhead bin, as I recall. Publicly discussed and documented cases of interference causing serious problems are fairly rare... it is unclear how many actual cases there have ever been. There's a web page at the FAA website that discusses it, and the events where interference is suspected. It's not common, but it's also not unheard of, although usually, it's just inferred that this is what happened. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS from a window seat
On 10/4/09 1:06 PM, Bill Hawkins b...@iaxs.net wrote: Group, As to interference with other GPS receivers, my son runs a deep-sea fishing party boat out of Ocean City, MD. He is famous for knowing where the fish will be. There may be 5 to 20 people on a 50' fiberglass boat using GPS units to log his fishing spots. He'd be delighted if those receivers interfered with each other. He sees no interference with his GPS navigation system. Interesting.. He's got an incentive to figure a way to prevent all those folks from knowing precisely where he is, while he still needs GPS to navigate there, so a simple short range jammer (leaving aside the legal issues about jamming in general) wouldn't serve. A GPS signal simulator with a bogus (but close) location would be useful, and might actually fly under the Part 15 rules. The radiated power would be very low (a few mW) so it probably would fit in the not interfere rules, in general (e.g. You can radiate on your own property, e.g. In an anechoic chamber for testing, it's only if you interfere with someone outside your boundary that it gets sticky). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS from a window seat
But that doesn't change the fact that if a drunk businessman or a bored 6 year old with a new toy can stealthily endanger all the passengers on a plane, the responsibility - and liability - should be with the aircraft designer. Bringing it back to the normal topic at hand, I wonder - if you had a radio receiver tuned to WWV, and a GPS with a 1pps, if you could see the relativistic effect of flying at 500 knots at 30K feet and log it on your computer? 500 kts = about 250 m/s. C^2 = 9E16 m^2/s^2 V^2/C^2 = 6.2E4/9E16 = .6E-12 A pretty small thing to look for Uncertainty in frequency from WWV due to ionospheric issues is on the order of 0.1 to 1 Hz. Call it about 0.1 ppm for the 10 MHz signal. Doppler effect on frequency from WWV is 2.5E2/3E8 = 1E-5 (10 ppm), which is orders of magnitude larger than anything else you're going to see. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
