Re: [time-nuts] GPS lock of the FE5680. Current experiment and question
All these different suggestions build down to one thing, the precision with which you measure the phase when you sample it each second. The single flip flop will tell you which half cycle. a simple two bit counter made with two '74 FFs tells you which half cycle and with direction. The "best" maybe is if you let the PPS set a FF and the 10MHz reset it. The FF's output gates a constant current to a capacitor and charges it to some voltage. Then you measure that with a 10-bit ADC. This measures the phase to maybe 1%, gives you direction and is pretty cheap to build Let's see if I have the numbers right? If you check a 10MHz signal once per second with just the FF then you have 1E-7. You would need 1000 seconds for 1E-10. But if you measure phase to 1/10th of a cycle you get to 1E-10 ten faster. Right? Chris Albertson Redondo Beach, California ___ 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 lock of the FE5680. Current experiment and question
On Fri, 10 Feb 2012 18:19:53 -0800, Hal Murray wrote: >> Flip-flops hardened against metastability are available. > >Do you have a part number in mind? Some logic families are better than others. In general you want faster ones with shorter setup and hold times. On Semiconductor has an interesting application note with some test data. http://www.onsemi.com/pub_link/Collateral/AN1504-D.PDF National mentions "metastable hardened" in this 74HCT74 data sheet. Notice the guaranteed worst case propagation delays: http://eshop.engineering.uiowa.edu/NI/pdfs/00/53/DS005360.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] Leap seconds now showing on GPS satellites
It got here around 2785 seconds UTC after midnight on Feb 10th. (unless I fatfingered something) >From a NTP log file while watching a HP Z3801A. The "+" says insert a leap second. 55967 2401.038 127.127.26.1 T2201202100040023001028 64 0 55967 2465.034 127.127.26.1 T220120210004106300102D 64 0 55967 2529.037 127.127.26.1 T2201202100042103001029 64 0 55967 2593.038 127.127.26.1 T220120210004314300102E 64 0 55967 2657.033 127.127.26.1 T2201202100044183001033 64 0 55967 2721.037 127.127.26.1 T220120210004522300102F 64 0 55967 2785.037 127.127.26.1 T22012021000462630+102F 64 0 55967 2849.033 127.127.26.1 T22012021000473030+102B 64 0 55967 2913.034 127.127.26.1 T22012021000483430+1030 64 0 55967 2977.033 127.127.26.1 T22012021000493830+1035 64 0 55967 3041.033 127.127.26.1 T22012021000504230+1028 64 0 55967 3105.039 127.127.26.1 T22012021000514630+102D 64 0 55967 3169.033 127.127.26.1 T22012021000525030+1029 64 0 55967 3233.033 127.127.26.1 T22012021000535430+102E 64 0 -- 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.
Re: [time-nuts] GPS lock of the FE5680. Current experiment and question
You don't. That's why the HC4046 has 3 phase comparators. Different strokes for different folks... From: Hal Murray To: Discussion of precise time and frequency measurement Sent: Fri, February 10, 2012 9:35:01 PM Subject: Re: [time-nuts] GPS lock of the FE5680. Current experiment and question paulsw...@gmail.com said: > Hang on here. If the signal was 10 MHz for ref and RB its easy as suggested > here XOR gates and such. Assume I have 2 signals that are (very) close to 10 MHz and I get to read their XOR. How do I know which one is faster? -- 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] GPS lock of the FE5680. Current experiment and question
paulsw...@gmail.com said: > Hang on here. If the signal was 10 MHz for ref and RB its easy as suggested > here XOR gates and such. Assume I have 2 signals that are (very) close to 10 MHz and I get to read their XOR. How do I know which one is faster? -- 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.
Re: [time-nuts] GPS lock of the FE5680. Current experiment and question
paulsw...@gmail.com said: > Why 24 bits because it was pretty easy using 74hc596 8 bit counters with > latch and tristate outputs. Unfortunately the schematics are on paper at the > moment scribbles. But the cntrs are stacked on top each other as a unit and > soldered together. Only a few pins are not such as clock output enable and > such its quite simple. The 8 bits feed a port on the micro so I can get the > bytes. As for smaller countes indeed at this point its clear it could have > been even 1. I can't quite figure out what you are planning... Someplace, you have to consider metastability. Since you can't read all 3 chips in the counter at the same time, you also have to consider the carry from one chip to the next. I assume you are familiar with the classic trick of reading high, low, high, and trying again if the high samples are not the same. (That's for a 2 byte counter.) You can probably use the same ideas to avoid metastability by reading the low byte twice. If you get X, X or X, X+1, you probably have a valid reading. You still have the problem of reading both counters in sync. I'd probably try something like read: high-1, mid-1, low-1, low-1, mid-1, high-1, high-2, mid-2, low-2, low-2, mid-2, high-2 and then try again if any of the pairs didn't match. (Where "match" allows the low byte to advance by 1.) The key idea is that the counters will be read with an offset but the offset will be a constant which won't cause any problems. -- 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.
Re: [time-nuts] GPS lock of the FE5680. Current experiment and question
Hi If you go to a sample and hold, just use it to capture the voltage of the 10 MHz sine wave. That is one way to do an analog phase detector... Bob On Feb 10, 2012, at 8:54 PM, David wrote: > Flip-flops hardened against metastability are available. > > I would try a track and hold before a sample and hold but I wonder how > accurate it would be having to rely on the oscillator waveform. Fast > sample gates are non-trivial. I believe better than either would be a > time to voltage converter which just needs a set/reset flip-flop and > switched current integrator. Dig up the schematic for a Tektronix > 2232 oscilloscope for a "simple" example that yields 50pS resolution > using late 1980s technology. > > I just recently ventured into the sampling oscilloscope world with a > 7S11/S-4/7T11 setup. The S-4 uses a traveling wave gate which avoids > the fast sample gate problem but I would consider that the far side of > esoteric since I have not studied it in detail yet. > > On Fri, 10 Feb 2012 17:23:46 -0800 (PST), Robert LaJeunesse > wrote: > >> Sampling unsychronized signals with a DFF is problematic, since if setup and >> hold times are not met the output could oscillate and maybe settle to some >> noise >> driven value. I can't help thinking that if you are sampling the 10MHz >> signal at >> 1Hz the only way to get reasonable resolution is to sample the 10MHz >> sinewave >> signal's fastest part with tight analog sample & hold. Looking at the result >> wih >> a slow, low-cost 24-bit A to D chip would give tremendous resolution - if >> the >> drift was low enough. Use the ADC over a sub-range and add a small micro for >> noise filtering and averaging and one can achieve measurements result in the >> 10s >> of femtoseconds. >> >> >> From: David >> To: Discussion of precise time and frequency measurement >> Sent: Fri, February 10, 2012 8:10:56 PM >> Subject: Re: [time-nuts] GPS lock of the FE5680. Current experiment and >> question >> >> All you need for this is the flip-flop. Clock the flip-flop with the >> 1 PPS signal and capture whether the oscillator is leading or lagging. >> This requires the 10 MHz oscillator to be within 1 Hz but if you >> divide it down before the comparison, you can extend this range as >> needed to handle wider initial oscillator frequencies and larger >> amounts of PPS jitter. >> >> The simple GPSDO design in QST a couple years ago did something like >> this. > > ___ > 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] GPS lock of the FE5680. Current experiment and question
Hi If your GPS puts out 1 pps, you get one sample per second out of your phase detector. If it's digital you get a one or a zero. Dead time between edges is 50 ns. You throw away a lot of the accuracy of GPS by doing it this way. With an analog detector you would know how early or late you are. With better data in, the average will be more accurate. Bob On Feb 10, 2012, at 7:35 PM, Chris Albertson wrote: > On Fri, Feb 10, 2012 at 3:52 PM, Bob Camp wrote: >> Hi >> >> I think you will need some sort of analog detector to get what you are >> looking for. > > I don't think it needs to be analog. For example you can xor the two > 10MHz signals and then sample the digital xor output then deduce its > duty cycle by counting how many samples are 1 and how many are 0. > You'd expect an equal number if there is a phase lock. Might be best > to sample a-periodically at random. > > Many designs put a low pass filter on the XOR but I think random > polling allows the software to adjust the time constant and is cheaper > to implement. I think you'd have the latch the xor in a flipflop as > it would move to fast for a uP to read. > > > Chris Albertson > Redondo Beach, California > > ___ > 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] GPS lock of the FE5680. Current experiment and question
> Flip-flops hardened against metastability are available. Do you have a part number in mind? The only data sheet that I remember for a part that looked interesting was actually 2 FFs inside one package. For something like that, you save the prop time of the output driver and the input receiver relative to a classic pair of FFs. That should be a significant improvement relative to the classic pair of FFs. Other than that, the parts I remember were nothing special. Maybe the designers actually understood metastability and did some testing and wrote a data sheet with promises. I don't remember the details. There is no cure for metastability. You can only make the probability lower. There are two ways to make things better. One is to get faster logic and run it at the old clock rate. The other is to wait longer. If you wait long enough, you can make the probability low enough, as in a MTBF of greater than the age of the universe. Modern high speed logic has a (much) faster settling time which makes the window smaller, but then we run the whole system at a faster clock rate so the probability of events per second stays roughly the same. -- 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.
Re: [time-nuts] GPS lock of the FE5680. Current experiment and question
On Fri, 10 Feb 2012 19:54:11 -0600, David wrote: >Flip-flops hardened against metastability are available. > >I would try a track and hold before a sample and hold but I wonder how >accurate it would be having to rely on the oscillator waveform. Fast >sample gates are non-trivial. I believe better than either would be a >time to voltage converter which just needs a set/reset flip-flop and >switched current integrator. Dig up the schematic for a Tektronix >2232 oscilloscope for a "simple" example that yields 50pS resolution >using late 1980s technology. My mistake. That should be 500pS. ___ 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 lock of the FE5680. Current experiment and question
Good question and the reason for the large counter. If locked its a hard number and a number above or below that number is how far its off and in what direction. Yup 24 bits was a bit crazy but it wasn't anything to do. That said a single 8 bit counter would have been fine given the stability the RB seems to have all by itself. On Fri, Feb 10, 2012 at 8:28 PM, Chris Albertson wrote: > On Fri, Feb 10, 2012 at 5:10 PM, David wrote: > > > All you need for this is the flip-flop. Clock the flip-flop with the > > 1 PPS signal and capture whether the oscillator is leading or lagging. > > I can see how this can detect lock. If the FF is the same each second > you are good. But if it changes how do you know the direction of the > change? > > -- > > Chris Albertson > Redondo Beach, California > > ___ > 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] GPS lock of the FE5680. Current experiment and question
On Fri, 10 Feb 2012 17:28:53 -0800, Chris Albertson wrote: >On Fri, Feb 10, 2012 at 5:10 PM, David wrote: > >> All you need for this is the flip-flop. Clock the flip-flop with the >> 1 PPS signal and capture whether the oscillator is leading or lagging. > >I can see how this can detect lock. If the FF is the same each second >you are good. But if it changes how do you know the direction of the >change? It only detects if the phase difference is leading or lagging. Assuming that the frequency is locked, the FF should return a 50/50 distribution when phased locked. ___ 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 lock of the FE5680. Current experiment and question
Flip-flops hardened against metastability are available. I would try a track and hold before a sample and hold but I wonder how accurate it would be having to rely on the oscillator waveform. Fast sample gates are non-trivial. I believe better than either would be a time to voltage converter which just needs a set/reset flip-flop and switched current integrator. Dig up the schematic for a Tektronix 2232 oscilloscope for a "simple" example that yields 50pS resolution using late 1980s technology. I just recently ventured into the sampling oscilloscope world with a 7S11/S-4/7T11 setup. The S-4 uses a traveling wave gate which avoids the fast sample gate problem but I would consider that the far side of esoteric since I have not studied it in detail yet. On Fri, 10 Feb 2012 17:23:46 -0800 (PST), Robert LaJeunesse wrote: >Sampling unsychronized signals with a DFF is problematic, since if setup and >hold times are not met the output could oscillate and maybe settle to some >noise >driven value. I can't help thinking that if you are sampling the 10MHz >signal at >1Hz the only way to get reasonable resolution is to sample the 10MHz sinewave >signal's fastest part with tight analog sample & hold. Looking at the result >wih >a slow, low-cost 24-bit A to D chip would give tremendous resolution - if the >drift was low enough. Use the ADC over a sub-range and add a small micro for >noise filtering and averaging and one can achieve measurements result in the >10s >of femtoseconds. > > >From: David >To: Discussion of precise time and frequency measurement >Sent: Fri, February 10, 2012 8:10:56 PM >Subject: Re: [time-nuts] GPS lock of the FE5680. Current experiment and >question > >All you need for this is the flip-flop. Clock the flip-flop with the >1 PPS signal and capture whether the oscillator is leading or lagging. >This requires the 10 MHz oscillator to be within 1 Hz but if you >divide it down before the comparison, you can extend this range as >needed to handle wider initial oscillator frequencies and larger >amounts of PPS jitter. > >The simple GPSDO design in QST a couple years ago did something like >this. ___ 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 lock of the FE5680. Current experiment and question
On Fri, Feb 10, 2012 at 5:10 PM, David wrote: > All you need for this is the flip-flop. Clock the flip-flop with the > 1 PPS signal and capture whether the oscillator is leading or lagging. I can see how this can detect lock. If the FF is the same each second you are good. But if it changes how do you know the direction of the change? -- Chris Albertson Redondo Beach, California ___ 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 lock of the FE5680. Current experiment and question
Sampling unsychronized signals with a DFF is problematic, since if setup and hold times are not met the output could oscillate and maybe settle to some noise driven value. I can't help thinking that if you are sampling the 10MHz signal at 1Hz the only way to get reasonable resolution is to sample the 10MHz sinewave signal's fastest part with tight analog sample & hold. Looking at the result wih a slow, low-cost 24-bit A to D chip would give tremendous resolution - if the drift was low enough. Use the ADC over a sub-range and add a small micro for noise filtering and averaging and one can achieve measurements result in the 10s of femtoseconds. From: David To: Discussion of precise time and frequency measurement Sent: Fri, February 10, 2012 8:10:56 PM Subject: Re: [time-nuts] GPS lock of the FE5680. Current experiment and question All you need for this is the flip-flop. Clock the flip-flop with the 1 PPS signal and capture whether the oscillator is leading or lagging. This requires the 10 MHz oscillator to be within 1 Hz but if you divide it down before the comparison, you can extend this range as needed to handle wider initial oscillator frequencies and larger amounts of PPS jitter. The simple GPSDO design in QST a couple years ago did something like this. ___ 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] GPS lock of the FE5680. Current experiment and question
On Fri, 10 Feb 2012 16:35:26 -0800, Chris Albertson wrote: >On Fri, Feb 10, 2012 at 3:52 PM, Bob Camp wrote: >> Hi >> >> I think you will need some sort of analog detector to get what you are >> looking for. > >I don't think it needs to be analog. For example you can xor the two >10MHz signals and then sample the digital xor output then deduce its >duty cycle by counting how many samples are 1 and how many are 0. >You'd expect an equal number if there is a phase lock. Might be best >to sample a-periodically at random. > >Many designs put a low pass filter on the XOR but I think random >polling allows the software to adjust the time constant and is cheaper >to implement. I think you'd have the latch the xor in a flipflop as >it would move to fast for a uP to read. All you need for this is the flip-flop. Clock the flip-flop with the 1 PPS signal and capture whether the oscillator is leading or lagging. This requires the 10 MHz oscillator to be within 1 Hz but if you divide it down before the comparison, you can extend this range as needed to handle wider initial oscillator frequencies and larger amounts of PPS jitter. The simple GPSDO design in QST a couple years ago did something like this. ___ 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 lock of the FE5680. Current experiment and question
On Fri, Feb 10, 2012 at 4:48 PM, paul swed wrote: > Hang on here. If the signal was 10 MHz for ref and RB its easy as suggested > here XOR gates and such. > > But the GPS is a 1 second interval and the RB is 10 Mhz. So the GPS 1 > second is the reference. Thats much harder then dealing with 100 Hz or up. Why is the count so low? If a counter i being driven by a 10MHz signal it would reach "3" quickly. What I read was that one signal was incrementing it while another was decrementing and then after a long time the result was close to zero. Redondo Beach, California ___ 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 lock of the FE5680. Current experiment and question
Hang on here. If the signal was 10 MHz for ref and RB its easy as suggested here XOR gates and such. But the GPS is a 1 second interval and the RB is 10 Mhz. So the GPS 1 second is the reference. Thats much harder then dealing with 100 Hz or up. So the answer I have seen which seems to fit is Bobs comments earlier. That is the numbers/thinking are right and it would take a really long gate time to become more accurate. I may get a slight improvement by using the better reciever that has a tighter 1 PPS. I do see what I am betting is a jitter on the Novatel. But its not a timing receiver. Regards Paul. On Fri, Feb 10, 2012 at 7:35 PM, Chris Albertson wrote: > On Fri, Feb 10, 2012 at 3:52 PM, Bob Camp wrote: > > Hi > > > > I think you will need some sort of analog detector to get what you are > looking for. > > I don't think it needs to be analog. For example you can xor the two > 10MHz signals and then sample the digital xor output then deduce its > duty cycle by counting how many samples are 1 and how many are 0. > You'd expect an equal number if there is a phase lock. Might be best > to sample a-periodically at random. > > Many designs put a low pass filter on the XOR but I think random > polling allows the software to adjust the time constant and is cheaper > to implement. I think you'd have the latch the xor in a flipflop as > it would move to fast for a uP to read. > > > Chris Albertson > Redondo Beach, California > > ___ > 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] GPS lock of the FE5680. Current experiment and question
On Fri, Feb 10, 2012 at 3:52 PM, Bob Camp wrote: > Hi > > I think you will need some sort of analog detector to get what you are > looking for. I don't think it needs to be analog. For example you can xor the two 10MHz signals and then sample the digital xor output then deduce its duty cycle by counting how many samples are 1 and how many are 0. You'd expect an equal number if there is a phase lock. Might be best to sample a-periodically at random. Many designs put a low pass filter on the XOR but I think random polling allows the software to adjust the time constant and is cheaper to implement. I think you'd have the latch the xor in a flipflop as it would move to fast for a uP to read. Chris Albertson Redondo Beach, California ___ 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 lock of the FE5680. Current experiment and question
Good comments so I am on target in thinking. Why 24 bits because it was pretty easy using 74hc596 8 bit counters with latch and tristate outputs. Unfortunately the schematics are on paper at the moment scribbles. But the cntrs are stacked on top each other as a unit and soldered together. Only a few pins are not such as clock output enable and such its quite simple. The 8 bits feed a port on the micro so I can get the bytes. As for smaller countes indeed at this point its clear it could have been even 1. But thats the fun of doing it. Regards Paul. On Fri, Feb 10, 2012 at 6:52 PM, Bob Camp wrote: > Hi > > I think you will need some sort of analog detector to get what you are > looking for. > > Bob > > > > On Feb 10, 2012, at 6:34 PM, Chris Albertson > wrote: > > > On Fri, Feb 10, 2012 at 2:53 PM, paul swed wrote: > >> Just for fun have built up a simple multi-chip project to try my hand at > >> locking the FE5680 using the external efc connection mod. mentioned in > >> time-nuts. Typical counter micro rs 232 port stuff. > >> > >> Essentially the system is 2 X 24 bit counters that toggle back and > fourth > >> every interval selectable from 1 to 65000 seconds accumulating counts. > I am > >> measuring the 10 Mhz of the RB and using a novatel superstar II GPS > rcvr. I > >> do have a better timing rcvr but this was handy and at this point most > >> likely good enough. > > > > Do you ever need such a large counter? As you say the counts are only > > small integers. If the two are close they would not overflow even a > > 4-bit counter. One way to go is to have only a two bit counter (just > > a pair of flop flops) and end the integration as soon as the second > > bit flips. If you are building a FLL you only need to know which is > > faster. > > > > If you want faster convergence I think you have to measure relative > > phase and use a PLL. Then you don't need to wait for a full cycle. > > Maybe only a few degrees of phase difference is enough > > > > My plan is to use the 74HC4096 is the detector. It has the required > > flip flops inside. Use that to dive the RB5680 and then when they are > > reasonably close the 74HC4096 also contains an XOR type phase > > detector, so switch to that. > > > > Chris Albertson > > Redondo Beach, California > > > > ___ > > 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] GPS lock of the FE5680. Current experiment and question
Hi I think you will need some sort of analog detector to get what you are looking for. Bob On Feb 10, 2012, at 6:34 PM, Chris Albertson wrote: > On Fri, Feb 10, 2012 at 2:53 PM, paul swed wrote: >> Just for fun have built up a simple multi-chip project to try my hand at >> locking the FE5680 using the external efc connection mod. mentioned in >> time-nuts. Typical counter micro rs 232 port stuff. >> >> Essentially the system is 2 X 24 bit counters that toggle back and fourth >> every interval selectable from 1 to 65000 seconds accumulating counts. I am >> measuring the 10 Mhz of the RB and using a novatel superstar II GPS rcvr. I >> do have a better timing rcvr but this was handy and at this point most >> likely good enough. > > Do you ever need such a large counter? As you say the counts are only > small integers. If the two are close they would not overflow even a > 4-bit counter. One way to go is to have only a two bit counter (just > a pair of flop flops) and end the integration as soon as the second > bit flips. If you are building a FLL you only need to know which is > faster. > > If you want faster convergence I think you have to measure relative > phase and use a PLL. Then you don't need to wait for a full cycle. > Maybe only a few degrees of phase difference is enough > > My plan is to use the 74HC4096 is the detector. It has the required > flip flops inside. Use that to dive the RB5680 and then when they are > reasonably close the 74HC4096 also contains an XOR type phase > detector, so switch to that. > > Chris Albertson > Redondo Beach, California > > ___ > 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] Leap seconds now showing on GPS satellites
I saw it yesterday on my TBolt. Last time I looked was a couple of weeks ago. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of k4...@aol.com Sent: Friday, February 10, 2012 2:16 PM To: 'Discussion of precise time and frequencymeasurement' Subject: [time-nuts] Leap seconds now showing on GPS satellites I see page 18 subframe 4 is now broadcasting a pending leap second being transmitted by the GPS sats. I had checked it earlier this week and they were still transmitting the old data. But sometime between Monday and today they changed it. For those with receivers or software programs monitoring such, it should now show a pending leap second! 73's, Doug Connected by DROID on Verizon Wireless ___ 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] GPS lock of the FE5680. Current experiment and question
On Fri, Feb 10, 2012 at 2:53 PM, paul swed wrote: > Just for fun have built up a simple multi-chip project to try my hand at > locking the FE5680 using the external efc connection mod. mentioned in > time-nuts. Typical counter micro rs 232 port stuff. > > Essentially the system is 2 X 24 bit counters that toggle back and fourth > every interval selectable from 1 to 65000 seconds accumulating counts. I am > measuring the 10 Mhz of the RB and using a novatel superstar II GPS rcvr. I > do have a better timing rcvr but this was handy and at this point most > likely good enough. Do you ever need such a large counter? As you say the counts are only small integers. If the two are close they would not overflow even a 4-bit counter. One way to go is to have only a two bit counter (just a pair of flop flops) and end the integration as soon as the second bit flips. If you are building a FLL you only need to know which is faster. If you want faster convergence I think you have to measure relative phase and use a PLL. Then you don't need to wait for a full cycle. Maybe only a few degrees of phase difference is enough My plan is to use the 74HC4096 is the detector. It has the required flip flops inside. Use that to dive the RB5680 and then when they are reasonably close the 74HC4096 also contains an XOR type phase detector, so switch to that. Chris Albertson Redondo Beach, California ___ 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 lock of the FE5680. Current experiment and question
Hi Without seeing the schematic it's a little hard to be sure this is all correct... If it is all based on 10 MHz, then yes you are doing it all modulo 100 ns. To get 1 part in 1x10^13 you would need 100,000 seconds. If that drives the LSB of a 16 bit counter for the DAC you would take a very long time to get to mid scale on the DAC. Even if you drive at the 100 second point, you would take about 3,200,000 seconds to get to mid scale. Bob On Feb 10, 2012, at 5:53 PM, paul swed wrote: > Just for fun have built up a simple multi-chip project to try my hand at > locking the FE5680 using the external efc connection mod. mentioned in > time-nuts. Typical counter micro rs 232 port stuff. > > Essentially the system is 2 X 24 bit counters that toggle back and fourth > every interval selectable from 1 to 65000 seconds accumulating counts. I am > measuring the 10 Mhz of the RB and using a novatel superstar II GPS rcvr. I > do have a better timing rcvr but this was handy and at this point most > likely good enough. > > My question is this. It seems that the system must use pretty large > accumulation times like 1000 or 1 seconds and higher to see the drift > in 1 sample. > > I think this actually all makes sense. Since the frequency accumulating is > 1 x 10^ 7 and the gate so far is 1 X 10^3 or the total resolution is 1 X 10 > 10th. Essentially accumulating 3 or so counts and averaging most likely > only gets the lock down to 1 X10^10 or a bit more perhaps. Using a > accumulate of 10,000 would be the 11th. > Is my logic on target here. > > I only see a few counts one way or the other when I purposely increase or > decrease the RB offset. But it does indeed go in the correct directions. I > can adjust the dac by the drift and time method to get down in the -12th > region. So essentially the eyeball method is pretty good. > > If this is all correct then for a given accumulated time there is an exact > 24 bit number to always drive the RB to. I have an excel that figures out > that number for any accumulation time is. > > By the way took Berts suggestion some weeks back of using the LTC1655 16 > bit Vdac. Talk about easy to work with and in a 8 pin DIP. > > > Appreciate any guidance. Thanks. > Regards > Paul > WB8TSL > ___ > 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] GPS lock of the FE5680. Current experiment and question
Just for fun have built up a simple multi-chip project to try my hand at locking the FE5680 using the external efc connection mod. mentioned in time-nuts. Typical counter micro rs 232 port stuff. Essentially the system is 2 X 24 bit counters that toggle back and fourth every interval selectable from 1 to 65000 seconds accumulating counts. I am measuring the 10 Mhz of the RB and using a novatel superstar II GPS rcvr. I do have a better timing rcvr but this was handy and at this point most likely good enough. My question is this. It seems that the system must use pretty large accumulation times like 1000 or 1 seconds and higher to see the drift in 1 sample. I think this actually all makes sense. Since the frequency accumulating is 1 x 10^ 7 and the gate so far is 1 X 10^3 or the total resolution is 1 X 10 10th. Essentially accumulating 3 or so counts and averaging most likely only gets the lock down to 1 X10^10 or a bit more perhaps. Using a accumulate of 10,000 would be the 11th. Is my logic on target here. I only see a few counts one way or the other when I purposely increase or decrease the RB offset. But it does indeed go in the correct directions. I can adjust the dac by the drift and time method to get down in the -12th region. So essentially the eyeball method is pretty good. If this is all correct then for a given accumulated time there is an exact 24 bit number to always drive the RB to. I have an excel that figures out that number for any accumulation time is. By the way took Berts suggestion some weeks back of using the LTC1655 16 bit Vdac. Talk about easy to work with and in a 8 pin DIP. Appreciate any guidance. Thanks. Regards Paul WB8TSL ___ 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] Leap seconds now showing on GPS satellites
Paul, I am looking at the data from the satellites and it shows dtls=16, WNt=139, WNlsf=158, DN=7. Connected by DROID on Verizon Wireless -Original message- From: Poul-Henning Kamp To: Discussion of precise time and frequency measurement Sent: Fri, Feb 10, 2012 20:33:56 GMT+00:00 Subject: Re: [time-nuts] Leap seconds now showing on GPS satellites In message , "k4...@aol.com" writes: I see page 18 subframe 4 is now broadcasting a pending leap second being transmitted by the GPS sats. I had checked it earlier this week and they were still transmitting the old data. But sometime between Monday and today they changed it. For those with receivers or software programs monitoring such, it should now show a pending leap second! It does: NTPns > show oncore 0 serial port = /dev/cuad5 state = 12 visible/track/lock = 10/8/0 dop = 0.0 [m] 2012-02-10 20:32:58.000836713 Leap second info: 2012-07-01 00:00:00 INSERT 12194822 seconds (141 days) from now lat = 199461973 (55.406104), lon = 40823017 (11.339727), ht 9071 (90.71) http://maps.google.com/maps?ll=55.406104,11.339727&spn=0.03,0.08&t=k rcv_status = 0x8 = AcqSat/PosHold utc_offset = 15 site_survey = 2 (~0 sec left) Sat Dopler Elev Azi Health Mode SigStr IODE Status Offset 9 2117 57 280 00 850 0a2 0.150998000 12 3630 19 223 00 846 0a2 0.201329648 15 -1549 59 203 00 853 0a2 0.251661296 17 1039 39 95 00 851 0a2 0.285215728 18 -1198 25 274 00 850 0a2 0.301992944 22 1007 17 317 00 850 0a2 0.369101808 27182 83 285 00 850 0a2 0.452987888 28 -2682 33 58 00 849 0a2 0.469765104 -- 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] Morion MV89 output level?
I've tried both the MV89a and the Oscilloquartz 8663 (I think UCT is the same or very close) with the Thunderbolt. The Oscilloquartz does not fit any of the OCXO thru-hole combinations but the MV89a does fit one of the OCXO variations that TB accommodates. That makes for a very clean/compact replacement for the standard TB oscillator. You have to be s careful when wiring an OCXO off-board for ground bounce and other minute disturbances to the EFC. The MV89a as a TB on-board replacement is the only way I could get superb PPT stability out to TC=1000 sec. Even without active disciplining, either oscillator has very good long-term stability. I have a related question, probably directed to Said, on the Fury OEM board. The MV89a seems to work ok at 10.5 V and draws ~970ma on warm-up, settling out at ~350ma at this lower supply voltage. Is that initial current draw excessive for the Fury OCXO supply? I would like to use the on-board supply so the current draw can provide the feedback for TEMPCO. I'm using NTC thermistors strapped to the OCXO case otherwise like I have done with an 10811. The current approach would seem much better correlated. Regards... Don - Original Message - From: John Miles To: 'Discussion of precise time and frequency measurement' Sent: Friday, February 10, 2012 3:28 AM Subject: Re: [time-nuts] Morion MV89 output level? > Did you ever run any tests on those UCT double oven OCXOs? Only to the extent of running a short (10-minute) HDEV test after a ~2 hour warmup, to see if it was capable of anything interesting near t=10s to t=30s. It showed about 2E-12, and the PN was nothing special, so I didn't do anything else with it. I'll leave one running for a few days and try it. >I've found > them to be freaky-stable long term. I have retrofitted a lot of Tek > DC510/5010 counters with them and after over two years, the last digit is > still right on. They would probably be good for homebrew GPSDOs, given their small size. Perhaps a Thunderbolt refit. -- john ___ 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] Leap seconds now showing on GPS satellites
In message , "k4...@aol.com" writes: >I see page 18 subframe 4 is now broadcasting a pending leap second being >transmitted by the GPS sats. I had checked it earlier this week and they >were still transmitting the old data. But sometime between Monday and today >they changed it. For those with receivers or software programs monitoring >such, it should now show a pending leap second! It does: NTPns > show oncore 0 serial port = /dev/cuad5 state = 12 visible/track/lock = 10/8/0 dop = 0.0 [m] 2012-02-10 20:32:58.000836713 Leap second info: 2012-07-01 00:00:00 INSERT 12194822 seconds (141 days) from now lat = 199461973 (55.406104), lon = 40823017 (11.339727), ht 9071 (90.71) http://maps.google.com/maps?ll=55.406104,11.339727&spn=0.03,0.08&t=k rcv_status = 0x8 = AcqSat/PosHold utc_offset = 15 site_survey = 2 (~0 sec left) Sat Dopler Elev Azi Health Mode SigStr IODE Status Offset 9 2117 57 280 00 850 0a2 0.150998000 12 3630 19 223 00 846 0a2 0.201329648 15 -1549 59 203 00 853 0a2 0.251661296 17 1039 39 95 00 851 0a2 0.285215728 18 -1198 25 274 00 850 0a2 0.301992944 22 1007 17 317 00 850 0a2 0.369101808 27182 83 285 00 850 0a2 0.452987888 28 -2682 33 58 00 849 0a2 0.469765104 -- 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] Leap seconds now showing on GPS satellites
I see page 18 subframe 4 is now broadcasting a pending leap second being transmitted by the GPS sats. I had checked it earlier this week and they were still transmitting the old data. But sometime between Monday and today they changed it. For those with receivers or software programs monitoring such, it should now show a pending leap second! 73's, Doug Connected by DROID on Verizon Wireless ___ 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] Using digital broadcast TV for timing?
Hi I suspect that if you went into the GPS jamming business that the mob of lawyers would be even more scary than the stuff being dropped on your antennas... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Thursday, February 09, 2012 4:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Using digital broadcast TV for timing? On 02/09/2012 07:21 PM, Chris Albertson wrote: > On Wed, Feb 8, 2012 at 11:02 PM, Hal Murray wrote: >> >>> Other than LightSquared, an event that made GPS go away would most likely >>> eliminate most interest in ultra accuracy time keeping. >> > > By "went away", I meant locally, as be being jammed or spoofed. > Possibly a car drives into a tunnel and then from the car's point of > view GPS "goes away". > > From a military point of view all it takes to knock out GPS is to > suicide truck-bomb both ground control stations or simply jam the GPS > uplinks so the stations are unable to send commands. But The > question was more theoretical then practical. Let's assume that the physical safety of the ground control center is there, and just have a look at the jamming of up-links. Jamming the up-links would be a bit of a difficult task, since there is not one but several up-links, also you would need to high-energy jam all the birds as you would not know when they would get their commands. Add their capability of cross-link communication and ability to uphold a decent situation in autonav for ground station outage of up to 180 days. Oh, both uplink and cross-link is encrypted and fairly jam-resistant. Cross-link has nulls towards earth and only a half-decent gain in certain angles. All that comes out of public sources. It would take a bit of resources to do a global GPS outage, and to maintain it you would expose yourself over a long time such that you would be found and well, let's assume that your antennas will not take kindly to the things being dropped at it. Regional outages is much easier. 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] Low-Cost Rubidium Performance
Hi I think we have enough data on current batch of FE-5680A rubidiums to guess that the ADEV plots on it's data sheet could only have been done in a constant temperature / environmental chamber... That said, I see no reason it will not meet the actual spec limits over the temperature range. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Thursday, February 09, 2012 9:19 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low-Cost Rubidium Performance Let me strengthen the argument below. Let's say you are building and selling Rb units to the telcom industry and you've spec'd your product for use in the range of -25C to +85C. Now you want to include an ADEV plot in your sales literature. Should you place the unit in an environmental controlled box while you measure it?I think you'd be accused of fraud if you did not state that the plot is not representative of the full temperature spec. I think in order to be valid you always have to state the test conditions but you can use ANY test condition, Place it outdoors, in a lab or what ever but just say what you did and then your plot has meaning. I think the converse to true, that without knowing the test conditions the plot is little meaning. > Why? Unless the unit is spec'd for use only at a constant temperature, > temperature variations are something it needs to deal with, and should be > included in any measurement of how good it is. In what way is temperature > variability special, that it shouldn't be included in ADEV measurements, but > all other contributors to variability should be? Certainly, there may be a > large non-random component to temperature (diurnal, annual, in many > environments), but there's also a significant part which is random - should > you somehow correct for one, but not the other? > > Shouldn't one expect the ADEV be better for a double oven OCXO than for a > bare crystal? > > The only issue I see is it may make fair comparison difficult, unless units > are compared under identical conditions. > > ___ > 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. -- Chris Albertson Redondo Beach, California ___ 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] Low-Cost Rubidium Performance
Hi Have I seen system bandwidth in published data? - pretty much never. Kudos to Symmetricom for putting it up on the display on the 5125. The system bandwidth debate goes back well into the 1960's. Pretty much every paper Dave Allan ever presented up through the 1980's, he got a question about bandwidth from the floor. I don't ever remember there being a definitive reply back in that era. Confidence bounds - same thing. How many points before you even display the data? If I'm using 3 points and you are using 100 the error bars will be a bit different. The reply to that question was generally - you really should have 100 or more points. I doubt we would see much 100,000 second data if people got rigorous on that By no means am I saying that ADEV shows all issues on all devices. We are in agreement there. My point is that people should know what you did to your data before you put it up on display. I have indeed seen people use a *lot* higher order fits than a simple linear estimator. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Thursday, February 09, 2012 9:12 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Low-Cost Rubidium Performance On 02/10/2012 02:31 AM, Bob Camp wrote: > Hi > > To add another wrinkle to this. > > Correcting ADEV for systematic errors and then not mentioning you did so strikes is something I find a bit problematic. If say you decide to take out 13th order drift, you should say you did so. The discussion of what to correct and how is older than ADEV. Since there is no "standard" set of corrections, one should be clear about what was done. Agreed, but even if we know that system bandwidth affects low-tau noise-forms, when did you last see the bandwidth given? Confidence bounds is another issue. But my main point is that you still look at the same damn plot rather than looking at some other plot for the other effects. The point is to separate them in order to clearer see each of them. For short-term, noise dominates, and depending on where we are on the spectra the ADEV or phase-noise plots serves us best. TIE curves is interesting, but MTIE curves adds a certain aspect, drift analysis curves another aspect etc. For jitter, separation of random noise and deterministic noise is am important to properly engineer the system. MTIE is another of those. I love my ADEVs, but as my suppliers know, it's not the only thing I ask for in an oscillator. How does my phase shift as the temperature cycles? ADEV won't tell me, but I bet the guy in the next cubicle can enlighten you if needed. This is all about understanding the limitations of the tools we have, so we use them for what they do best. ADEV is a great tool, just don't over use it. Whenever someone use their favorite tool (say ADEV, FFT or Object Oriented programming) for everything and everything needs to be answered by it, then the big warnings-bells goes off in the back of my head. As great as it ever is, know the limits of what you use... 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] science projects
On 2/10/12 2:05 AM, Chris Dawes wrote: Thanks Hal, Will have to visit next time I am in San Fran sounds interesting Makes a nice, but busy, day to do the Exploratorium and the California Academy of Sciences/Steinhart Aquarium. They're pretty close to each other, so it's not like you have to drive across town. ___ 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] science projects
On 2/10/12 1:37 AM, Hal Murray wrote: It's the "international science and engineering fair", so both kinds show up. The line between applied science and engineering is pretty fuzzy. There is another category. I'm not sure what the right term is. How about "just having fun"? Most definitely.. I think it's neat to see an experiment or demo that is well done. I expect a kid will have fun and learn a lot setting one up. With luck, some of both the fun and learning will rub off on other kids. yes, and that is something to be encouraged. However, science fairs ARE competitive, so what you want is "original" and "fun". Entrants who had fun working on their project ALWAYS place better than those slogging it out because they think it will burnish their college app or because it's an assignment. (My worst performance in 6 years of competition was when the other ideas for that year didn't pan out, and I had to put something together in a hurry.) The best entrants are the ones who are curious about everything, found something they wanted to investigate, know an amazing amount of obscure background information, and went about it in a competent way. It's the classic "that's funny" or "I wish it would do X" thing. I use demo to refer to an experiment that doesn't involve taking data. You just observe that if I do X, Y happens. Or if I make X bigger, Y gets bigger. Or qualitative vs quantitative. this is a good distinction. What wins (leaving aside the pedagogical value aspect) is quantitative. "Are redheads taller than blondes?" can be done both ways. If the question is reformulated as "Are redheads *significantly* taller than blondes? and is my school different from the population at large?" you've got the beginnings of a good project. I'm probably biased. A friend works at the Exploratorium. For those of you who don't know about it, it's the great grandaddy of the hands-on science museums. They have hundreds of exhibits. It's highly recommended if you ever get to San Francisco. Frank Oppenheimer had a real vision to get that going. It's a wonderful place. Paul teaches science to high-school science teachers. A lot of that involves showing them low cost experiments/demos. The teachers are always finding new/neat ways to do things. Yes.. and that's ever more important. My daughter's 8th grade physical sciences teacher was far better at imparting the fundamentals of chemistry than her 10th grade Chemistry teacher. That's something that comes with experience and enthusiasm and confidence, 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] science projects
Thanks Hal, Will have to visit next time I am in San Fran sounds interesting Chris -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Friday, 10 February 2012 8:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] science projects > It's the "international science and engineering fair", so both kinds > show up. > The line between applied science and engineering is pretty fuzzy. There is another category. I'm not sure what the right term is. How about "just having fun"? I think it's neat to see an experiment or demo that is well done. I expect a kid will have fun and learn a lot setting one up. With luck, some of both the fun and learning will rub off on other kids. I use demo to refer to an experiment that doesn't involve taking data. You just observe that if I do X, Y happens. Or if I make X bigger, Y gets bigger. I'm probably biased. A friend works at the Exploratorium. For those of you who don't know about it, it's the great grandaddy of the hands-on science museums. They have hundreds of exhibits. It's highly recommended if you ever get to San Francisco. Paul teaches science to high-school science teachers. A lot of that involves showing them low cost experiments/demos. The teachers are always finding new/neat ways to do things. -- 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] science projects
> It's the "international science and engineering fair", so both kinds show > up. > The line between applied science and engineering is pretty fuzzy. There is another category. I'm not sure what the right term is. How about "just having fun"? I think it's neat to see an experiment or demo that is well done. I expect a kid will have fun and learn a lot setting one up. With luck, some of both the fun and learning will rub off on other kids. I use demo to refer to an experiment that doesn't involve taking data. You just observe that if I do X, Y happens. Or if I make X bigger, Y gets bigger. I'm probably biased. A friend works at the Exploratorium. For those of you who don't know about it, it's the great grandaddy of the hands-on science museums. They have hundreds of exhibits. It's highly recommended if you ever get to San Francisco. Paul teaches science to high-school science teachers. A lot of that involves showing them low cost experiments/demos. The teachers are always finding new/neat ways to do things. -- 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.
Re: [time-nuts] Morion MV89 output level?
> Did you ever run any tests on those UCT double oven OCXOs? Only to the extent of running a short (10-minute) HDEV test after a ~2 hour warmup, to see if it was capable of anything interesting near t=10s to t=30s. It showed about 2E-12, and the PN was nothing special, so I didn't do anything else with it. I'll leave one running for a few days and try it. >I've found > them to be freaky-stable long term. I have retrofitted a lot of Tek > DC510/5010 counters with them and after over two years, the last digit is > still right on. They would probably be good for homebrew GPSDOs, given their small size. Perhaps a Thunderbolt refit. -- john ___ 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] science projects
> The best inventions are the ones that nobody ever thought to ask for. If > Edison had done marketing studies, he would have spent his life designing > incremental improvements to gas lights. Nobody asked him to invent the > electric light. First let me say that what I'm about to write is completely nit picking, but this something i feel i have to do. :) Edison did not invent the electric light, Humphrey Davy was credited in the early 1800's for the electric arc light so obviously Edison has simply improved the electric light. I believe a more accurate statement in this regard would be something such as "Edison created a longer lasting electric light". Even this is subject to debate as there were at least five others between Davy and Edison who attempted to build a longer lasting light. All of the work of these men were published in the scientific journals and i suspect that Edison was well aware of the previous work. The reason i mention this is because i believe that science and engineering are of the same phenomena, and this phenomena is sitting on the shoulders of many great men. Science / engineer is just like an electron, one way it is particle, and another it is wave. Of if you're a quantum type of person, it exists because you are there to observe it. 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.
