[time-nuts] Practical considerations making a lab standard with an LTE lite
I would like to make a unit with multiple 10 MHz 50 Ohm outputs to feed my various bits of test equipment. I am thinking about some practical considerations. 1) It would be great if there was a circuit published which can give 50 Ohn output impedance from a 12-15 power supply, which a) Doesn't load the TCXO b) Doesn't degrade the phase noise. c) Powered the LTE lite. Ideally one for both 10 20 MHz crystals. Better still if there was a PCB available. 2) How should I mount the components? My preference would be a metal box with * IEC mains socket * antenna input socket * 9-pin D for reading dats * 15 BNC's outputs With a power amplifier to provide the output for 15 sockets, some ventilation possibly requiring a small amount of forced air cooling would be needed. But given the TCXOs sensitivity to temperature changes, I don't know whether it might be preferable to mount the LTE lite in its own box without any power supplies in it - perhaps with some thermally insulting material around the LTE lite so the crystal doesn't experience any fast temperature changes. Then have the power hungry bits completely separately. I don't have a particularly big lab, so wherever I mount the LTE lite, the temperature is going to change with the air conditioning unit blows hot or cold There are fairly large temperature changes when I am not using the lab, as I don't run the air conditioning unit 24/7. I am interested in people's thoughts on the best way to go about this. For testing I have a couple of signal generators that have ovens that are powered 24/7. Also I should soon have the SR620. Dave. ___ 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] Practical considerations making a lab standard with an LTE lite
In message 20141123153744.biokf...@smtp16.mail.yandex.net, Charles Steinmetz writes: First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). [...] Charles' design has some good points, but I don't agree with it. What you are trying to do is to low-pass filter any thermal signals before they reach the LTE or OCXO. Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. (For LTE and OCXO it is probably less of a problem that changing power-disipation will have a outsized effect on the central temperature.) Here is a much simpler and likely cheaper way to do it: Put the LTE or OCXO in a small box of your choice. Even a cardboard box is fine. A little thermal insulation in the box is OK, but not too much, the heat must be able to get out. Find a medium sized cardboard box, something like a cubic feet or so. Place it where you want your house-standard, with some kind of thermal insulation under it, two layers of old rug will do fine. Lay a floor of bricks inside the box. Build a wall of bricks along the outside of the box. Place the smaller box in the hole in the middle, cut the corner of a brick to run the cables without too much leakage. Use a floortile as roof, possibly with a layer of bricks on top. Close the outher cardboard box with tape to minimize convection. Congratulations, you now have a cheap and incredibly efficient thermal low-pas filter, which will allow thermal energy to move in both directions -- eventually. The outher cardboard box is not optional, unless you replace it with some other mostly air-tight barrier. The little bit of insulation the outher cardboard adds are not a bad idea either, for instance it reduces the effect of sunlight hits the box at certain times of the day/year. But you can substitute any geological building material you have at hand for the bricks, because the trick is that geological building materials have just the right thermal properties we are looking for: Decent but not too good thermal conductivity with healthy dose of thermal mass. Cinderblocks comes with convenient interior holes premade. Aerated concrete blocks are also a candidate material but don't make it too thick since it insulates quite well, and paint the surface to bind the dust. -- 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.
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
Dave wrote But given the TCXOs sensitivity to temperature changes, I don't know whether it might be preferable to mount the LTE lite in its own box without any power supplies in it - perhaps with some thermally insulting material around the LTE lite so the crystal doesn't experience any fast temperature changes. First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). Use thermally insulating standoffs (teflon or nylon, with no metal through fasteners) to get the board in the middle of the volume of the box. Use a box a bit larger than you'd first think, so there is at least 1 of air on all 6 sides of the LTE board. Do NOT mount any part of the LTE board (connectors, etc.) directly to the box walls -- use pigtails for all connections. Do NOT use any insulation between the LTE and the box walls other than the 1+ of air. The mounting described above will add substantial thermal capacitance to the LTE board (good) without adding significant thermal resistance (bad). For further discussions of this issue, search the list archives for thermal capacitance and thermal mass. Now, mount the cast box (plus any thermal mass you add to it -- see below) so that IT is thermally isolated from the overall enclosure (or, if it sits out in the open, thermally isolated from anything solid). The air space in the enclosure isolates the oscillator from the cast box and the box is sufficiently massive that its temperature cannot change nearly as fast as ambient. The thermal mass of the cast box can be adjusted by adding thermal mass to it as desired. The goal is for the box temperature to change only by changes in ambient AIR temperature, and the LTE board to change only by changes in the AIR temperature inside the cast box. This integrates any changes to the LTE board temperature with a very long time constant, which allows the GPS discipline to track and cancel the temperature changes. (If you mount an ovenized oscillator this same way, it integrates any changes to the OCXO temperature so that the oven control loop can track and cancel any changes to the crystal temperature.) You can, of course, improve things even further by making sure the ambient air temperature surrounding the cast box changes slowly, or not at all. But the technique described above can be counted on to reduce thermal effects in most OCXOs or GPSDOs to better (often much better) than the 1e-13 level unless the ambient temperature changes MUCH more and MUCH faster than any change we wouild consider normal for a living space. This is true whether the cast box is mounted out in the open, or inside an overall enclosure with other electronics. Best regards, Charles ___ 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] Practical considerations making a lab standard with an LTE lite
NIST did something similar for their WWWV site, where they used bottled water in its staple packaging to build a thermal mass. They measured how their atomic clocks and rig behaved before and after, and could see the difference. Very neat way of using off the (store)shelf components for a test. Another aspect is to think about what kind of heating/coolling you have. If it can act more as a proportional system rather than bang-bang regulations, it won't produce as drastic swings for you. Cheers, Magnus On 11/23/2014 02:32 PM, Poul-Henning Kamp wrote: In message 20141123153744.biokf...@smtp16.mail.yandex.net, Charles Steinmetz writes: First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). [...] Charles' design has some good points, but I don't agree with it. What you are trying to do is to low-pass filter any thermal signals before they reach the LTE or OCXO. Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. (For LTE and OCXO it is probably less of a problem that changing power-disipation will have a outsized effect on the central temperature.) Here is a much simpler and likely cheaper way to do it: Put the LTE or OCXO in a small box of your choice. Even a cardboard box is fine. A little thermal insulation in the box is OK, but not too much, the heat must be able to get out. Find a medium sized cardboard box, something like a cubic feet or so. Place it where you want your house-standard, with some kind of thermal insulation under it, two layers of old rug will do fine. Lay a floor of bricks inside the box. Build a wall of bricks along the outside of the box. Place the smaller box in the hole in the middle, cut the corner of a brick to run the cables without too much leakage. Use a floortile as roof, possibly with a layer of bricks on top. Close the outher cardboard box with tape to minimize convection. Congratulations, you now have a cheap and incredibly efficient thermal low-pas filter, which will allow thermal energy to move in both directions -- eventually. The outher cardboard box is not optional, unless you replace it with some other mostly air-tight barrier. The little bit of insulation the outher cardboard adds are not a bad idea either, for instance it reduces the effect of sunlight hits the box at certain times of the day/year. But you can substitute any geological building material you have at hand for the bricks, because the trick is that geological building materials have just the right thermal properties we are looking for: Decent but not too good thermal conductivity with healthy dose of thermal mass. Cinderblocks comes with convenient interior holes premade. Aerated concrete blocks are also a candidate material but don't make it too thick since it insulates quite well, and paint the surface to bind the dust. ___ 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] practical details on generating artificial flicker noise
I'm writing a short simulation program to generate samples from a analog system with some op amps, etc., and I'm wondering if anyone has some practical experience on picking parameters for the generator. I'm generating minutes worth of data sampled at 1 kHz, and my opamps have their flicker/white knee at around 3-4 Hz (at least that's what the LT1679 data sheet claims.. we shall see if the model matches the data sheet matches what I measure on the actual hardware) I'm using a Barnes-Jarvis (or Barnes-Greenhall) type generator for the flicker noise, which basically sums up a bunch of stages to create an arbitrarily smooth representation. See threads: https://www.febo.com/pipermail/time-nuts/2010-April/046926.html https://www.febo.com/pipermail/time-nuts/2013-November/081534.html The actual PTTI paper is http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_19.pdf has the details http://tycho.usno.navy.mil/ptti/1992papers/Vol 24_44.pdf has some corrections, but is a partial page.. You need to pick a few parameters: how many stages to cover your frequency band of interest, how big the frequency steps are (e.g. octaves), and where's the top band filter cutoff (typically 0.3 to 0.5 relative to the sample rate) If you picked 4 stages, with a starting frequency of 0.4, and octaves(R=2), then the individual filter cutoffs would be 0.4 0.2 0.1 0.05 I'm interested in the behavior down in the 1 Hz and below range, say, to 0.01 Hz. So to cover 0.01 Hz to 1000Hz, one would need about 16-17 octaves which is an enormous number of stages and I've got to believe you'd have all sorts of numerical problems And I think I don't need to do this I can add white noise to establish the noise floor to match lab measurements (there's sources other than the op amps) for higher frequencies, say in the 20-1000 Hz area. It would seem, then, that I can start the first filter at around 5 Hz and go down from there, if my assumption that most of the flicker noise is coming from the opamp and it's flicker noise comes above the thermal noise at 3-4 Hz. Then, going in, say, octave jumps, I can get down to 0.01 Hz in about 8 steps. (this seems to match Figure 2 in the paper.. they used a 8 stages with a frequency ratio of 2.4, and the spectrum looks pretty flat for a good 5 decades. I suppose I could just write it and see what comes out, but if someone out there has worked with this kind of thing before, a bit of practical guidance would be useful. ___ 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] Lucent KS-24361 Ref1 burnin after 1.8 weeks
Hi On Nov 22, 2014, at 11:02 PM, paul swed paulsw...@gmail.com wrote: Thanks I just like the idea that its leveling out instead of always climbing. Yup, that’s what you want to see. Granted there are all these noisy spikes but I think thats just the way it is and most likely not bad at all. It needs to correct for the impact of temperature on the OCXO. That will always create “noise” on the DAC line. Without knowing the real EFC bits and the sensitivity it’s tough to figure out what’s going on. Its very steady against the Z3801. By that I mean on a scope at 5ns/div I might guess its 8 hours to move a division. It does move but you can not see it. Only over great deals of time. Then the question. Who is actually moving? If they both are locked to GPS. —and— If they both are CDMA cell tower parts —and — They are not broke. Then: The answer is that neither one is really moving. They both are holding +/- 100 ns (likely much less) relative to GPS. The real challenge. Not for me at least. Oh yes fire up the TBolt and have one more confusing answer. Think I will skip that. Confusion is what Time Nuts is all about. Where’s your sense of adventure Bob Regards Paul. On Sat, Nov 22, 2014 at 9:04 PM, Bob Camp kb...@n1k.org wrote: Hi Since the data comes out of the box in percent, the whole “counts” thing is a bit of a fiction. The conversion to counts or bits was done based on observations of earlier boxes. That conversion may or may not apply to the 3810/11/12’s. Right now, there’s no reason to think that it’s wrong for these boxes. I’d just be careful watching the data. Bob On Nov 22, 2014, at 8:49 PM, paul swed paulsw...@gmail.com wrote: It is getting better today about 80-90 count positive. On Thu, Nov 20, 2014 at 7:08 PM, Bob Camp kb...@n1k.org wrote: Hi I’ve posted a couple of phase plots of a few of the KS-24361 compared to a 5071A and to each other via a TimePod. Since phase is essentially time, it’s a good way to get an idea of what’s going on. Spot checks with a terminal program and SCPI appeared to show reasonable agreement between phase and what the status screen reported. I can probably come up with more data if the world has not gotten tired of looking at plots. I suspect that for long term data, there is some sort of “simple” SCPI that just gets the time error. The full status screen is not very good for that kind of use. It takes more than a second to compile inside the box. Bob On Nov 20, 2014, at 7:00 PM, Anthony Roby ar...@antamy.com wrote: Bob - what data are you capturing / measuring? I was thinking of just writing a simple capture program from the unit and analyzing it in Excel. When you say the status screen correspons to the data you've measured, what is it that you are comparing? Anthony -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Thursday, November 20, 2014 5:05 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Lucent KS-24361 Ref1 burnin after 1.8 weeks Hi Based on what I ??ve seen on multiple boxes, I believe that the graph you have been looking at for TI is messed up due to a software bug. Checking things with a terminal program, the status screen corresponds pretty well to the data I ??ve measured. Bob On Nov 20, 2014, at 4:40 PM, paul swed paulsw...@gmail.com wrote: I have been snapping pix so can compare now. Getting better. Regards Paul On Thu, Nov 20, 2014 at 12:14 PM, Anthony Roby ar...@antamy.com wrote: I'll fire up my lab PC and take a more recent screenshot of my data - when I last looked the EFC was a straight line and PPS TI / s had settled down but was still noisy. -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Thursday, November 20, 2014 10:24 AM To: Time-nuts Subject: [time-nuts] Lucent KS-24361 Ref1 burnin after 1.8 weeks As suggested by Bob and others the REF1 new out of the box needs time to burn in. At 1.8 weeks now I can see the EFC settling down towards a straight line. To start I was about 800 counts per day rising. Today 150 and rising. So it is slowly shifting towards what a z3801 as an example will do. Also ultimately it will look like an example Antony sent me. Simply noisy. The 3801 is fairly smooth. So I sense my earlier concern of a Bad box is wrong. Pretty happy about that. 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.
Re: [time-nuts] ocxo
Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham d...@montana.com wrote: So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is out of tolerance. All self tests pass with flying colors, autocal works as well. So the best parts are OK. Does anyone: 1) have a spare Isotemp OCXO36-53 10.000 MHz p/n 6-00051? 2) know the specs, ie the input voltage/current and the control voltage span and direction? pinout? I have some Morion mv-89's and could easily cobble one in if it will work. Apparently a correct oscillator must be in place to use an external source, if I read the manual right. 3) do we have a source for the schematics for the SR 620? The FTS 4060 is up, pumpin' and firmly locked. At least for now. That dealer was not lyin' Much thanks to all of you. The adventure continues -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.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. ___ 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. -- The power of accurate observation is commonly called cynicism by those
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
All: I am enjoying this thread. These are all very interesting ideas. Hoping to power up my first unit later today I'm putting my LTE-Lite in the recommended HAMMOND box. That takes care of the box with air. I was then considering proportional heating of the surface of the box, like I did long ago with some GUNNPLEXERS -- seemed to work pretty well. Then this whole assembly goes inside two or four inches of the foam insulation. Now, the question becomes, to what temperature to heat it? With a crystal, I'd plot /f/ vs. /T/, and look for minimum slope. How to do that with LTE-Lite -- plot /efc/ vs /T/ and look for either center of range or minimum slope?? Thoughts? Jim wb4...@amsat.org On 11/23/2014 9:03 AM, Magnus Danielson wrote: NIST did something similar for their WWWV site, where they used bottled water in its staple packaging to build a thermal mass. They measured how their atomic clocks and rig behaved before and after, and could see the difference. Very neat way of using off the (store)shelf components for a test. Another aspect is to think about what kind of heating/coolling you have. If it can act more as a proportional system rather than bang-bang regulations, it won't produce as drastic swings for you. Cheers, Magnus On 11/23/2014 02:32 PM, Poul-Henning Kamp wrote: In message 20141123153744.biokf...@smtp16.mail.yandex.net, Charles Steinmetz writes: First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). [...] Charles' design has some good points, but I don't agree with it. What you are trying to do is to low-pass filter any thermal signals before they reach the LTE or OCXO. Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. (For LTE and OCXO it is probably less of a problem that changing power-disipation will have a outsized effect on the central temperature.) Here is a much simpler and likely cheaper way to do it: Put the LTE or OCXO in a small box of your choice. Even a cardboard box is fine. A little thermal insulation in the box is OK, but not too much, the heat must be able to get out. Find a medium sized cardboard box, something like a cubic feet or so. Place it where you want your house-standard, with some kind of thermal insulation under it, two layers of old rug will do fine. Lay a floor of bricks inside the box. Build a wall of bricks along the outside of the box. Place the smaller box in the hole in the middle, cut the corner of a brick to run the cables without too much leakage. Use a floortile as roof, possibly with a layer of bricks on top. Close the outher cardboard box with tape to minimize convection. Congratulations, you now have a cheap and incredibly efficient thermal low-pas filter, which will allow thermal energy to move in both directions -- eventually. The outher cardboard box is not optional, unless you replace it with some other mostly air-tight barrier. The little bit of insulation the outher cardboard adds are not a bad idea either, for instance it reduces the effect of sunlight hits the box at certain times of the day/year. But you can substitute any geological building material you have at hand for the bricks, because the trick is that geological building materials have just the right thermal properties we are looking for: Decent but not too good thermal conductivity with healthy dose of thermal mass. Cinderblocks comes with convenient interior holes premade. Aerated concrete blocks are also a candidate material but don't make it too thick since it insulates quite well, and paint the surface to bind the dust. ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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] Practical considerations making a lab standard with an LTE lite
Dave wrote: It would be great if there was a circuit published which can give 50 Ohn output impedance from a 12-15 power supply, which a) Doesn't load the TCXO b) Doesn't degrade the phase noise. WRT loading the TCXO, someone should establish quantitatively how high the load impedance must be to avoid significant negative effects. Said mentioned 1M ohm, which is the other common lab instrument input impedance besides 50 ohms, but I would be very surprised to find that the load resistance really needs to be that high. Why does this matter? The lower the impedance you load the oscillator with, the more power you get out of it; therefore, the lower the power gain that is necessary to develop an output signal you can use to feed the external world -- and, consequently, the less noise you are forced to add to the signal during amplification. I would recommend testing the LTE with a 1M ohm load resistance to establish a baseline. 1) Measure and record the outout voltage. 2) Measure and record the levels of the first few harmonics in relation to the carrier. 3) Get a qualitative feel for the levels of higher harmonics. Then, start reducing the load impedance (I would start with 10k ohms, then move to 1k ohms), paying attention to: a) The output voltage b) The levels of the first few harmonics in relation to the carrier, and c) The levels of higher harmonics, if they increase faster than the first few as the load resistance decreases. When you get to the point where the output voltage drops to 1/2 of the 1M ohm voltage, you have reached the output impedance of the LTE board (matched source and load impedances). As a general matter, it would not be useful to use a load impedance lower than this. If you reach this point without a significant increase in the output harmonics, great -- use this impedance as the input resistance of your buffer amplifier. If, however, the harmonics increase faster (with decreasing load resistance) and become objectionable before you reach the 1/2 voltage point, you must decide how much distortion is acceptable and use the load resistance that produces this level of harmonics. In this case, you trade off distortion and noise. So, the first step is for someone to do the experiment and find out how low the input resistance of the buffer amp can be as a practical matter. Then, a buffer amp topology can be chosen for best performance with this input resistance. Also, determine how many oscillator-frequency outputs you need (including outputs that will feed dividers, multipliers, or other circuitry internal to the buffer box). This will also influence the optimum choice of buffer amp topology. Best regards, Charles ___ 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] Practical considerations making a lab standard with an LTE lite
Hi If you have a basement in your house / building —and — it’s dry and reasonably draft free (no garage doors opening up from time to time) — and — At least one side / corner is well buried in the ground — and — You can get at that corner / side. Move your thermal baffle gizmo up against that wall, move it into that corner. There is a lot more mass in the foundation of a building than anything you would want to lug around for a project. You still need to handle the issues on at least half the surface, that should be less trouble than doing the whole thing. There is another subtle advantage to this approach. The standard is out of the way. It’s not in the middle of the lab. It does not get bumped. It does not get sparked (unless you have full ESD protection in the lab …). It’s less likely to have random power cycle events due to cords being accidentally pulled. Even second order stuff related to ground loops from connecting and disconnecting cables may be reduced. “Just leave it alone” is much easier to do when the gizmo is surrounded by a pile of bricks. With a GPSDO, you don’t care (much) about the environmental swings from week to week or month to month. The GPS will take care of that. What you care about are the hour to hour or minute to minute movements. Those are the ones that the filter on an OCXO based unit will struggle with. Hotter in the summer / colder in the winter is not as big a deal as “cold when I come in / hot after I turn everything on”. One practical hint if you do try this: Put a cheap plastic bag around the gizmo and tape it up. It discourages the bug colonies. I have empirical evidence that this is a good idea ... Bob On Nov 23, 2014, at 9:03 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: NIST did something similar for their WWWV site, where they used bottled water in its staple packaging to build a thermal mass. They measured how their atomic clocks and rig behaved before and after, and could see the difference. Very neat way of using off the (store)shelf components for a test. Another aspect is to think about what kind of heating/coolling you have. If it can act more as a proportional system rather than bang-bang regulations, it won't produce as drastic swings for you. Cheers, Magnus On 11/23/2014 02:32 PM, Poul-Henning Kamp wrote: In message 20141123153744.biokf...@smtp16.mail.yandex.net, Charles Steinmetz writes: First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). [...] Charles' design has some good points, but I don't agree with it. What you are trying to do is to low-pass filter any thermal signals before they reach the LTE or OCXO. Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. (For LTE and OCXO it is probably less of a problem that changing power-disipation will have a outsized effect on the central temperature.) Here is a much simpler and likely cheaper way to do it: Put the LTE or OCXO in a small box of your choice. Even a cardboard box is fine. A little thermal insulation in the box is OK, but not too much, the heat must be able to get out. Find a medium sized cardboard box, something like a cubic feet or so. Place it where you want your house-standard, with some kind of thermal insulation under it, two layers of old rug will do fine. Lay a floor of bricks inside the box. Build a wall of bricks along the outside of the box. Place the smaller box in the hole in the middle, cut the corner of a brick to run the cables without too much leakage. Use a floortile as roof, possibly with a layer of bricks on top. Close the outher cardboard box with tape to minimize convection. Congratulations, you now have a cheap and incredibly efficient thermal low-pas filter, which will allow thermal energy to move in both directions -- eventually. The outher cardboard box is not optional, unless you replace it with some other mostly air-tight barrier. The little bit of insulation the outher cardboard adds are not a bad idea either, for instance it reduces the effect of sunlight hits the box at certain times of the day/year. But you can substitute any geological building material you have at hand for the bricks, because the trick is that geological building materials have just the right thermal properties we are looking for: Decent but not too good thermal conductivity with healthy dose of thermal mass. Cinderblocks comes with convenient interior holes premade. Aerated concrete blocks are also a candidate material but don't make it too thick since it insulates quite well, and paint the surface to bind the dust. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
Re: [time-nuts] practical details on generating artificial flicker noise
Hi About all I’d say is that if Jim Barnes said that’s the way to do it. then that’s the way to do it. There are only a very few people who I’d say that about. Bob On Nov 23, 2014, at 9:05 AM, Jim Lux jim...@earthlink.net wrote: I'm writing a short simulation program to generate samples from a analog system with some op amps, etc., and I'm wondering if anyone has some practical experience on picking parameters for the generator. I'm generating minutes worth of data sampled at 1 kHz, and my opamps have their flicker/white knee at around 3-4 Hz (at least that's what the LT1679 data sheet claims.. we shall see if the model matches the data sheet matches what I measure on the actual hardware) I'm using a Barnes-Jarvis (or Barnes-Greenhall) type generator for the flicker noise, which basically sums up a bunch of stages to create an arbitrarily smooth representation. See threads: https://www.febo.com/pipermail/time-nuts/2010-April/046926.html https://www.febo.com/pipermail/time-nuts/2013-November/081534.html The actual PTTI paper is http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_19.pdf has the details http://tycho.usno.navy.mil/ptti/1992papers/Vol 24_44.pdf has some corrections, but is a partial page.. You need to pick a few parameters: how many stages to cover your frequency band of interest, how big the frequency steps are (e.g. octaves), and where's the top band filter cutoff (typically 0.3 to 0.5 relative to the sample rate) If you picked 4 stages, with a starting frequency of 0.4, and octaves(R=2), then the individual filter cutoffs would be 0.4 0.2 0.1 0.05 I'm interested in the behavior down in the 1 Hz and below range, say, to 0.01 Hz. So to cover 0.01 Hz to 1000Hz, one would need about 16-17 octaves which is an enormous number of stages and I've got to believe you'd have all sorts of numerical problems And I think I don't need to do this I can add white noise to establish the noise floor to match lab measurements (there's sources other than the op amps) for higher frequencies, say in the 20-1000 Hz area. It would seem, then, that I can start the first filter at around 5 Hz and go down from there, if my assumption that most of the flicker noise is coming from the opamp and it's flicker noise comes above the thermal noise at 3-4 Hz. Then, going in, say, octave jumps, I can get down to 0.01 Hz in about 8 steps. (this seems to match Figure 2 in the paper.. they used a 8 stages with a frequency ratio of 2.4, and the spectrum looks pretty flat for a good 5 decades. I suppose I could just write it and see what comes out, but if someone out there has worked with this kind of thing before, a bit of practical guidance would be useful. ___ 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] Practical considerations making a lab standard with an LTE lite
In message c9e99c83-aaa9-4d50-9729-b86a79af2...@n1k.org, Bob Camp writes: At least one side / corner is well buried in the ground But be aware that such a corner may be dry only when empty. -- 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.
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
In message 20141123174632.kvk4s...@smtp18.mail.yandex.net, Charles Steinmetz writes: And good luck fitting a cubic foot box with a surround of bricks into a 3U rack cabinet, or any other relocatable (much less,semi-portable) enclosure. I didn't say it doesn't work, I said that I don't agree with it ;-) -- 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.
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
Hi What you have in the LTE is a TCXO rather than a bare crystal or an OCXO. It’s got a compensation circuit that corrects the FT curve of the crystal. The net result is likely a 5th or higher order curve when you plot frequency over temperature. Every TCXO off that production line will have a different curve. You would need a full characterization of that curve for your specific TCXO to pick an optimum point. With a GPSDO, taking care of the long term drift is not what you are after. The GPS does that. If the GPSDO is TCXO based, the the loop filter is going to be pretty fast. That is *not* a knock on the LTE part, it’s just physics. An OCXO part is a different beast. Each has their strong points. Don’t try to run the OCXO off batteries for a week … With a fast filter, temperature variations at the “per hour” level are not likely an issue. Once you get to the point that drafts are worked out, and that temperature change is slowed down, you are done. No need for anything more complex. Bob On Nov 23, 2014, at 9:30 AM, Jim Sanford wb4...@wb4gcs.org wrote: All: I am enjoying this thread. These are all very interesting ideas. Hoping to power up my first unit later today I'm putting my LTE-Lite in the recommended HAMMOND box. That takes care of the box with air. I was then considering proportional heating of the surface of the box, like I did long ago with some GUNNPLEXERS -- seemed to work pretty well. Then this whole assembly goes inside two or four inches of the foam insulation. Now, the question becomes, to what temperature to heat it? With a crystal, I'd plot /f/ vs. /T/, and look for minimum slope. How to do that with LTE-Lite -- plot /efc/ vs /T/ and look for either center of range or minimum slope?? Thoughts? Jim wb4...@amsat.org On 11/23/2014 9:03 AM, Magnus Danielson wrote: NIST did something similar for their WWWV site, where they used bottled water in its staple packaging to build a thermal mass. They measured how their atomic clocks and rig behaved before and after, and could see the difference. Very neat way of using off the (store)shelf components for a test. Another aspect is to think about what kind of heating/coolling you have. If it can act more as a proportional system rather than bang-bang regulations, it won't produce as drastic swings for you. Cheers, Magnus On 11/23/2014 02:32 PM, Poul-Henning Kamp wrote: In message 20141123153744.biokf...@smtp16.mail.yandex.net, Charles Steinmetz writes: First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). [...] Charles' design has some good points, but I don't agree with it. What you are trying to do is to low-pass filter any thermal signals before they reach the LTE or OCXO. Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. (For LTE and OCXO it is probably less of a problem that changing power-disipation will have a outsized effect on the central temperature.) Here is a much simpler and likely cheaper way to do it: Put the LTE or OCXO in a small box of your choice. Even a cardboard box is fine. A little thermal insulation in the box is OK, but not too much, the heat must be able to get out. Find a medium sized cardboard box, something like a cubic feet or so. Place it where you want your house-standard, with some kind of thermal insulation under it, two layers of old rug will do fine. Lay a floor of bricks inside the box. Build a wall of bricks along the outside of the box. Place the smaller box in the hole in the middle, cut the corner of a brick to run the cables without too much leakage. Use a floortile as roof, possibly with a layer of bricks on top. Close the outher cardboard box with tape to minimize convection. Congratulations, you now have a cheap and incredibly efficient thermal low-pas filter, which will allow thermal energy to move in both directions -- eventually. The outher cardboard box is not optional, unless you replace it with some other mostly air-tight barrier. The little bit of insulation the outher cardboard adds are not a bad idea either, for instance it reduces the effect of sunlight hits the box at certain times of the day/year. But you can substitute any geological building material you have at hand for the bricks, because the trick is that geological building materials have just the right thermal properties we are looking for: Decent but not too good thermal conductivity with healthy dose of thermal mass. Cinderblocks comes with convenient interior holes premade. Aerated concrete blocks are also a candidate material but don't make it too thick since it insulates quite well, and paint the surface to bind the dust.
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
I am scratching my head here. From what I see the LTE is a good unit but does swim around a bit. The conclusion I might get from this thread is that lots of insulation will fix that. I suspect not. The LTE in use down at 2.8 e-10 according to its output. I have put it in a small cardboard box with free standing air and some Styrofoam. Because thats what turned up in the basement. I have added heat to it. It sits on top the Lucent box thats on. :-) It still swims around. It moves forward and backwards stays steady. Random. Certainly not terrible. I just think as neat as bricks may be it would not help allot. The top of the thread is excellant about checking the TCXO output Z. Regards Paul WB8TSL On Sun, Nov 23, 2014 at 9:55 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20141123174632.kvk4s...@smtp18.mail.yandex.net, Charles Steinmetz writes: And good luck fitting a cubic foot box with a surround of bricks into a 3U rack cabinet, or any other relocatable (much less,semi-portable) enclosure. I didn't say it doesn't work, I said that I don't agree with it ;-) -- 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] Practical considerations making a lab standard with an LTE lite
Hi Yup, that’s another good reason for the plastic bag :) If moisture might be an issue in your area, cover up the corner for a while in the rainy season to check for that problem before the project begins. Depending on the bag is not a real good idea. Bob On Nov 23, 2014, at 9:50 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message c9e99c83-aaa9-4d50-9729-b86a79af2...@n1k.org, Bob Camp writes: At least one side / corner is well buried in the ground But be aware that such a corner may be dry only when empty. -- 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.
Re: [time-nuts] practical details on generating artificial flicker noise
Jim, Find myself providing guidance in both the 2010 and 2013 threads, and they are still valid starting-points. For music synthesizer applications, flicker noise have been done, such as on this schematic: https://rubidium.dyndns.org/~magnus/synths/friends/stopp/asm1ns.pdf The work is traceable back to the Barnes-Jarvis work. Might be fun to know. :) Anyway, yes, it would be reasonable that you would need that many sections if you really intend to cover the full range, but on the other hand, usually you have a corner from which white noise dominates, and you really don't need to do much more than an octave or two beyond that corner. Doing 16-17 sections is cheap today. The other approach is to read Chuck Greenhalls more recent papers and see if none of those methods is applicable to your needs. Also, remember that in the Barnes-Jarvis approach, the distance between upper and lower corners is separated from how tight variation is allowed, which is controlling how many sections you need. Plotting with a scale normalized with sqrt(f) helps in analysis. Thanks for reminding me that I should implement flicker noise generation. Cheers, Magnus On 11/23/2014 03:05 PM, Jim Lux wrote: I'm writing a short simulation program to generate samples from a analog system with some op amps, etc., and I'm wondering if anyone has some practical experience on picking parameters for the generator. I'm generating minutes worth of data sampled at 1 kHz, and my opamps have their flicker/white knee at around 3-4 Hz (at least that's what the LT1679 data sheet claims.. we shall see if the model matches the data sheet matches what I measure on the actual hardware) I'm using a Barnes-Jarvis (or Barnes-Greenhall) type generator for the flicker noise, which basically sums up a bunch of stages to create an arbitrarily smooth representation. See threads: https://www.febo.com/pipermail/time-nuts/2010-April/046926.html https://www.febo.com/pipermail/time-nuts/2013-November/081534.html The actual PTTI paper is http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_19.pdf has the details http://tycho.usno.navy.mil/ptti/1992papers/Vol 24_44.pdf has some corrections, but is a partial page.. You need to pick a few parameters: how many stages to cover your frequency band of interest, how big the frequency steps are (e.g. octaves), and where's the top band filter cutoff (typically 0.3 to 0.5 relative to the sample rate) If you picked 4 stages, with a starting frequency of 0.4, and octaves(R=2), then the individual filter cutoffs would be 0.4 0.2 0.1 0.05 I'm interested in the behavior down in the 1 Hz and below range, say, to 0.01 Hz. So to cover 0.01 Hz to 1000Hz, one would need about 16-17 octaves which is an enormous number of stages and I've got to believe you'd have all sorts of numerical problems And I think I don't need to do this I can add white noise to establish the noise floor to match lab measurements (there's sources other than the op amps) for higher frequencies, say in the 20-1000 Hz area. It would seem, then, that I can start the first filter at around 5 Hz and go down from there, if my assumption that most of the flicker noise is coming from the opamp and it's flicker noise comes above the thermal noise at 3-4 Hz. Then, going in, say, octave jumps, I can get down to 0.01 Hz in about 8 steps. (this seems to match Figure 2 in the paper.. they used a 8 stages with a frequency ratio of 2.4, and the spectrum looks pretty flat for a good 5 decades. I suppose I could just write it and see what comes out, but if someone out there has worked with this kind of thing before, a bit of practical guidance would be useful. ___ 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] Time tagging fpga
Anders, The counter runs on a Pipistrello. I looked at the information on the web about time taggers before starting. I decided to try an oversampling scheme described by a group of Italian? physicists for a multichannel time tagging instrument. They used 4x oversampling. My version is crude; it uses the 50 MHz on-board clock but of course could use an external clock source. The clock is multiplied to 1 GHz and then divided into four 125 Hz clocks phased 45 degrees apart. There is a fifth 125 MHz clock at 0 phase for the main counter and external interface. There are four channels, each with 3 bits for value and a forth bit indicating an event. The sixteen bits are followed by a 48 bit counter value. what, if any, signal conditioning do you have between the DMTD output and the FPGA? I was thinking about copying the CERN DIO design which looks like this: http://ibin.co/1iEwLuAUQYJ4 it has a fuse, a resistor to set the input impedance, protection diodes, and an ADCMP604 that outputs an LVDS pair to the FPGA. The CERN design is for a 125 MHz clock. What would be the preferred way to generate this for the Pipistrello, with an optional 10MHz reference input? OCXO at 10MHz and a ADF4351 PLL+VCO up to 125MHz? Does someone have a tested circuit that autodetects the external 10MHz and can switch between the OCXO and ext-ref? This yields 1 ns resolution (bin size) but the bins sizes are certainly not all equal. I have few means to check the accuracy but for my purposes (logging 100 Hz to 1 Hz zero crossings of a DMTD) it is certainly more accurate than I need. I have experimented with .5 ns bin sizes, also using the 8x oversampling with a 250 MHz clock. To keep the backend 125 MHz structure I used a two phase multiplexer to combine two successive samples. This runs but is not reliable and needs further work before it's useful. Did you post the schematic for your DMTD? Many of the time-to-digital papers calibrate the bin-width by collecting time-stamps from an asynchronous pulse-source. If the bins are equal you should get a flat histogram. Some use a ring-oscillator on the fpga for generating the asynchronous hits. Anders ___ 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] Practical considerations making a lab standard with an LTE lite
Poul-Henning wrote: Charles' design works great from the outside, but doesn't do anything with respect to the thermal energy expended by the encapsulated device themselves, which will cause convection in the inner box. I have been using the technique for 30+ years, including with many OCXOs (which, obviously, generate significant heat) and have never observed any problems of that nature at the 1e-13 level. I did consider the possibility when I first started doing it, and tested two potential fixes: (i) putting a fan inside the box to homogenize the internal temperature, and (ii) filling the air space inside the box with irregular solid shapes to break up the convection pattern. I tested both methods extensively with instrumented sources, in many variations (fan speeds and orientations, mass and porosity of passive internal shapes), and did not find any difference at the 1e-13 level. I have occasionally used an internal fan just on theoretical grounds, but I have never measured any practical difference. Thinking about it, this does not seem too surprising -- one would expect any convection to settle into a stable pattern and thus not to cause any temperature changes over time (once it is warm and settled). Whether this explains my results or some other effect predominates (for example, convection may move enough air in the limited space to achieve substantial isothermy), I have confirmed to my satisfaction that it is simply not a factor in practice at the levels we are concerned with. If you test the cast aluminum box method and find that your results do not accord with mine, please publish them and we can discuss what might account for the observed differences and how the method could be improved. Until then, you are just posting speculative musings on the subject based on no data, which does not seem helpful. And good luck fitting a cubic foot box with a surround of bricks into a 3U rack cabinet, or any other relocatable (much less, semi-portable) enclosure. Best regards, Charles ___ 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] Time tagging fpga
I was about to comment on this. As you interpolate among the 8 phases, time errors in the routing might need to compensated for in order to represent a flat stepping of time-compensation. It will not be perfect naturally. Cheers, Magnus On 11/23/2014 03:57 PM, Anders Wallin wrote: Anders, The counter runs on a Pipistrello. I looked at the information on the web about time taggers before starting. I decided to try an oversampling scheme described by a group of Italian? physicists for a multichannel time tagging instrument. They used 4x oversampling. My version is crude; it uses the 50 MHz on-board clock but of course could use an external clock source. The clock is multiplied to 1 GHz and then divided into four 125 Hz clocks phased 45 degrees apart. There is a fifth 125 MHz clock at 0 phase for the main counter and external interface. There are four channels, each with 3 bits for value and a forth bit indicating an event. The sixteen bits are followed by a 48 bit counter value. what, if any, signal conditioning do you have between the DMTD output and the FPGA? I was thinking about copying the CERN DIO design which looks like this: http://ibin.co/1iEwLuAUQYJ4 it has a fuse, a resistor to set the input impedance, protection diodes, and an ADCMP604 that outputs an LVDS pair to the FPGA. The CERN design is for a 125 MHz clock. What would be the preferred way to generate this for the Pipistrello, with an optional 10MHz reference input? OCXO at 10MHz and a ADF4351 PLL+VCO up to 125MHz? Does someone have a tested circuit that autodetects the external 10MHz and can switch between the OCXO and ext-ref? This yields 1 ns resolution (bin size) but the bins sizes are certainly not all equal. I have few means to check the accuracy but for my purposes (logging 100 Hz to 1 Hz zero crossings of a DMTD) it is certainly more accurate than I need. I have experimented with .5 ns bin sizes, also using the 8x oversampling with a 250 MHz clock. To keep the backend 125 MHz structure I used a two phase multiplexer to combine two successive samples. This runs but is not reliable and needs further work before it's useful. Did you post the schematic for your DMTD? Many of the time-to-digital papers calibrate the bin-width by collecting time-stamps from an asynchronous pulse-source. If the bins are equal you should get a flat histogram. Some use a ring-oscillator on the fpga for generating the asynchronous hits. Anders ___ 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] practical details on generating artificial flicker noise
On 11/23/14, 7:21 AM, Magnus Danielson wrote: Jim, Find myself providing guidance in both the 2010 and 2013 threads, and they are still valid starting-points. For music synthesizer applications, flicker noise have been done, such as on this schematic: https://rubidium.dyndns.org/~magnus/synths/friends/stopp/asm1ns.pdf The work is traceable back to the Barnes-Jarvis work. Might be fun to know. :) There's a bunch of schemes described at http://www.firstpr.com.au/dsp/pink-noise/ Some of which look remarkably like the Barnes, Jarvis, Greenhall approaches. Anyway, yes, it would be reasonable that you would need that many sections if you really intend to cover the full range, but on the other hand, usually you have a corner from which white noise dominates, and you really don't need to do much more than an octave or two beyond that corner. Doing 16-17 sections is cheap today. computationally, but any time I start down the path of implementing something where the literature has half a dozen stages and I'm going to be doubling or tripling that, you start to wonder about whether there's some numerical issue that will bite you. After all, that difference equation for the lowest frequency cutoff, with the high sample rate, has coefficients that are very close to 1 (The Barnes Greenhall paper appendix A shows a lot of zero values in the tabulated area, but they were using double precision and not printing all the digits) The other approach is to read Chuck Greenhalls more recent papers and see if none of those methods is applicable to your needs. Also, remember that in the Barnes-Jarvis approach, the distance between upper and lower corners is separated from how tight variation is allowed, which is controlling how many sections you need. Plotting with a scale normalized with sqrt(f) helps in analysis. yes.. the examples in the paper make that pretty clear.. 4 sections spread over 6 decades gets you a fair amount of variation. There's also, of course, all those notes about selecting an appropriate starting point by trial and error.. Which is probably why they wrote the analysis part of their code: make a run with one value, look at the plot, hmm, change a value, make a run, etc. Well.. I'm grinding through the implementation now.. in Python, as it happens, so I'm trying to figure out how to do it a Python-esque way, as opposed to my usual Fortran/Matlab in Python style. Seems one should be able to have nice abstracted filter sections that you can iterate through, etc. BTW, if anyone is going to implement the algorithm in the PTTI paper, you really need the Greenhall JPL report also, because a lot of the terminology and variables carry forward. http://ipnpr.jpl.nasa.gov/progress_report/42-77/77M.PDF (of course, as I think about it, if I need 60 seconds worth of samples at 1 kHz, that's only 60,000 samples, so I could just do it by generating 64k of white noise, FFTing, applying a -3dB/octave slope, and then inverse transforming.. And, since the FFT of white noise is white noise, it's really just taking N samples of white noise, applying the filter, and doing the transform to the time domain.) (yes, the FFT method was discussed in the earlier threads) ___ 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] Practical considerations making a lab standard with an LTE lite
The short-term performance is 10x worse if you don't shield the TCXO from air, even if the ambient air is still. I suggested Said sell the product with some sort of engineered shield in place. Instead each of us will solve the problem in our own way; which is ok for a dev kit. For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. The insulation may be found in convenient rolls at many local stores. I used TP, which for this application is an acronym for Thermal Paper. /tvb ___ 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] Practical considerations making a lab standard with an LTE lite
On 23 Nov 2014 14:45, Bob Camp kb...@n1k.org wrote: Hi If you have a basement in your house / building I do not. —and — it’s dry and reasonably draft free (no garage doors opening up from time to time) My lab is a room which is part of the garage! Just about everything is against me with this method, BUT you do give me an idea... You got me thinking about the possibility of actually mounting the TCXO burried in the ground! The temperature of that is not going to change very rapidly. FWIW, I know a guy that did work as an air conditioning engineer,, but now works for a company selling geothermal heating. He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. In a couple of years the temperature of the ground falls as the heat is extracted faster than it replenishes. So the efficiency falls off. I don't think that the TCXO would heat the ground faster than it dissipates away. Of course there would be some practical issues burying the TCXO, but those would not be insurmountable ones. I have no idea what depth might be needed. My wife thinks thinks I am a nutcase - that would only confirm it to her! Dave, G8WRB ___ 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] Low Additive Phase Noise 10 MHz Amps
What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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] rs-422 rs-232 to fast ethernet converter
Thanks all for the replies. After a couple of replies and the reference to terminal server a light bulb came on and put it all into perspective, including a vague recollection of some previous postings. cheers, Graham ve3gtc On 2014-11-22 19:59, Chris Albertson wrote: On Sat, Nov 22, 2014 at 2:47 PM, Graham planoph...@aei.ca wrote: I have been contemplating how I will would like to interface to the KS-23461 devices using rs-422. One option is a rs-422 to USB cable. Seems easy enough. But another option I keep stumbling across is a rs-422/rs-232 to fast ethernet such as: They are called a terminal server. It's a box with some serial ports and one Ethernet port. You access each port via telent protocol. You can buy these surplus on eBay or you can MAKE one very easy. All you need is any kind of small computer, a 10 year old notebook PC, a Rasbury Pi, or whatever, so long as it has both a network and a serial port. Run a Telnet SSH server on this and you are on-line and can access the device from any place on Earth.I would not buy a small computer for this but if you have one already then it is free. Telnet is very old. I remember using it first in the late 1970's back when the Internet was still called the Darpa Net and it only connected a few dozen computers. ___ 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] Time tagging fpga
Hi I believe the DMTD mentioned is the one done by Bill Riley. It’s at: http://www.wriley.com/A%20Small%20DMTD%20System.pdf That paper has way more info on the device and it’s signal processing than is worth going into on the list. There has been some discussion about the limiters used here on the list. I’d offer the quick summary of: they are adequate for the task. The active filtering ahead of the limiters is specific to a pre-defined range of offset frequencies / beat notes. It covers the ones most people use. The performance data shown on the site pretty well demonstrates that the box is up to any task a normal Time Nut would use it for. Those with multiple optical ion trap standards in the basement may need to tweak it a little :) Bob On Nov 23, 2014, at 9:57 AM, Anders Wallin anders.e.e.wal...@gmail.com wrote: Anders, The counter runs on a Pipistrello. I looked at the information on the web about time taggers before starting. I decided to try an oversampling scheme described by a group of Italian? physicists for a multichannel time tagging instrument. They used 4x oversampling. My version is crude; it uses the 50 MHz on-board clock but of course could use an external clock source. The clock is multiplied to 1 GHz and then divided into four 125 Hz clocks phased 45 degrees apart. There is a fifth 125 MHz clock at 0 phase for the main counter and external interface. There are four channels, each with 3 bits for value and a forth bit indicating an event. The sixteen bits are followed by a 48 bit counter value. what, if any, signal conditioning do you have between the DMTD output and the FPGA? I was thinking about copying the CERN DIO design which looks like this: http://ibin.co/1iEwLuAUQYJ4 it has a fuse, a resistor to set the input impedance, protection diodes, and an ADCMP604 that outputs an LVDS pair to the FPGA. The CERN design is for a 125 MHz clock. What would be the preferred way to generate this for the Pipistrello, with an optional 10MHz reference input? OCXO at 10MHz and a ADF4351 PLL+VCO up to 125MHz? Does someone have a tested circuit that autodetects the external 10MHz and can switch between the OCXO and ext-ref? This yields 1 ns resolution (bin size) but the bins sizes are certainly not all equal. I have few means to check the accuracy but for my purposes (logging 100 Hz to 1 Hz zero crossings of a DMTD) it is certainly more accurate than I need. I have experimented with .5 ns bin sizes, also using the 8x oversampling with a 250 MHz clock. To keep the backend 125 MHz structure I used a two phase multiplexer to combine two successive samples. This runs but is not reliable and needs further work before it's useful. Did you post the schematic for your DMTD? Many of the time-to-digital papers calibrate the bin-width by collecting time-stamps from an asynchronous pulse-source. If the bins are equal you should get a flat histogram. Some use a ring-oscillator on the fpga for generating the asynchronous hits. Anders ___ 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] Time tagging fpga
Hi If you want to go sub-nanosecond there are other ways to do the TDC in an FPGA. Numbers in the 60 to 140 ps range are fairly easy to hit with 2010 era FPGA’s. The results need to be corrected for temperature and voltage if either one moves very much. The routing delays drop out as part of the normal “random pulse” calibration process. Bob On Nov 23, 2014, at 10:55 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: I was about to comment on this. As you interpolate among the 8 phases, time errors in the routing might need to compensated for in order to represent a flat stepping of time-compensation. It will not be perfect naturally. Cheers, Magnus On 11/23/2014 03:57 PM, Anders Wallin wrote: Anders, The counter runs on a Pipistrello. I looked at the information on the web about time taggers before starting. I decided to try an oversampling scheme described by a group of Italian? physicists for a multichannel time tagging instrument. They used 4x oversampling. My version is crude; it uses the 50 MHz on-board clock but of course could use an external clock source. The clock is multiplied to 1 GHz and then divided into four 125 Hz clocks phased 45 degrees apart. There is a fifth 125 MHz clock at 0 phase for the main counter and external interface. There are four channels, each with 3 bits for value and a forth bit indicating an event. The sixteen bits are followed by a 48 bit counter value. what, if any, signal conditioning do you have between the DMTD output and the FPGA? I was thinking about copying the CERN DIO design which looks like this: http://ibin.co/1iEwLuAUQYJ4 it has a fuse, a resistor to set the input impedance, protection diodes, and an ADCMP604 that outputs an LVDS pair to the FPGA. The CERN design is for a 125 MHz clock. What would be the preferred way to generate this for the Pipistrello, with an optional 10MHz reference input? OCXO at 10MHz and a ADF4351 PLL+VCO up to 125MHz? Does someone have a tested circuit that autodetects the external 10MHz and can switch between the OCXO and ext-ref? This yields 1 ns resolution (bin size) but the bins sizes are certainly not all equal. I have few means to check the accuracy but for my purposes (logging 100 Hz to 1 Hz zero crossings of a DMTD) it is certainly more accurate than I need. I have experimented with .5 ns bin sizes, also using the 8x oversampling with a 250 MHz clock. To keep the backend 125 MHz structure I used a two phase multiplexer to combine two successive samples. This runs but is not reliable and needs further work before it's useful. Did you post the schematic for your DMTD? Many of the time-to-digital papers calibrate the bin-width by collecting time-stamps from an asynchronous pulse-source. If the bins are equal you should get a flat histogram. Some use a ring-oscillator on the fpga for generating the asynchronous hits. Anders ___ 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] Practical considerations making a lab standard with an LTE lite
In message canx10hb0kdrnaayzgvm1gkduj7gklth0acdxczg894hxbus...@mail.gmail.com , Dr. David Kirkby (Kirkby Microwave Ltd) writes: He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. There is a BIG difference between geothermal and ground heating. Geothermal means you drill at least 50m (Iceland) or more likely half a kilometer down, in order to harvest water at near boiling point from the Earths geological heat-sources (mostly uranium decay). Extracting more energy than available just means the temperature drops temporarily. It will increase again once you reduce the pump rate. Horizontal ground heat means that you are harvesting sunshine accumulated in the top one meter of the soil. Much of the energy is harvested from freezing the water around the pipe thus pulling out the relatively high melting energy of water. If you extract more energy than you deposit sunshine, you end up freezing a larger and larger volume of water/soil around the pipe and your compressor will eat a lot of electricity. In practice it looks like this: http://ing.dk/artikel/varmepumpe-mareridt-jordslange-var-dybfrossen-i-maj-113176 (The two pictures show the same pipe, with and without frozen ground.) Finally there is vertial ground heat where you drill down only about 40-80 meter, tapping heat mostly from ground water resources.Most places the ground water doesn't move fast enough to deliver the amounts of energy extracted, and over time the source returns unusably low temperature and must be abandonned. Typically after 25-30 years. -- 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.
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
On 23 Nov 2014 17:49, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message canx10hb0kdrnaayzgvm1gkduj7gklth0acdxczg894hxbus...@mail.gmail.com , Dr. David Kirkby (Kirkby Microwave Ltd) writes: He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. There is a BIG difference between geothermal and ground heating. Geothermal means you drill at least 50m (Iceland) or more likely half a kilometer down, in order to harvest water at near boiling point from the Earths geological heat-sources (mostly uranium decay). Sorry. What he installs is pipes in the ground in residential or industrial sites. Basically he says they work initially, but performance drops dramatically over a couple of years. If you extract more energy than you deposit sunshine, you end up freezing a larger and larger volume of water/soil around the pipe and your compressor will eat a lot of electricity. That is what he was saying. Dave. ___ 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] Practical considerations making a lab standard with an LTE lite
In message canx10hcaob-5gysbr7sdxwl7dyh7qubmhxwmi9xdrcf3mdm...@mail.gmail.com , Dr. David Kirkby (Kirkby Microwave Ltd) writes: Geothermal means you drill at least 50m (Iceland) or more likely half a kilometer down, in order to harvest water at near boiling point from the Earths geological heat-sources (mostly uranium decay). Sorry. What he installs is pipes in the ground in residential or industrial sites. Basically he says they work initially, but performance drops dramatically over a couple of years. That is not geothermal then, and yes, a LOT of those systems are badly underdimensioned. I've been researching this topic intensively because my new house will be heated that way. My conclusion, based on reading a lot of reports, is that there is no credible way to predict the performance. The wetter your soil the better, but that's about it. I'm going to overprovision by a factor two to be on the safe side, afterall it only costs EUR7 for each extra meter of pipe. -- 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.
Re: [time-nuts] rs-422 rs-232 to fast ethernet converter
Graham, There are a number of WiFi to serial modules like the one I use on my Thunderbolt monitor: The Microchip WiFly RN-XV-171. Once configured (typically using a PC), they will present a TCPIP port (TCP or UDP) from which you can get and send data directly to the serial port. Alternately, you can use Digi XBee modules that work like wireless RS232 isolators. I use the XSC Pro 900 MHz for a number of projects, including data loggers that are out of WiFi range. You can get well over a mile in open space with those. They are limited to 19200 bauds at the most. Didier KO4BB On November 22, 2014 4:47:15 PM CST, Graham planoph...@aei.ca wrote: I have been contemplating how I will would like to interface to the KS-23461 devices using rs-422. One option is a rs-422 to USB cable. Seems easy enough. But another option I keep stumbling across is a rs-422/rs-232 to fast ethernet such as: http://www.transition.com/TransitionNetworks/Products2/Family.aspx?Name=SDSFE3110-120 Frankly, I have no first hand knowledge or experience with these devices. First glance suggests that it might just be what I want - easy access to the KS-23461 ports through a connection to my local network without having a PC of some sort close by. So, any first hand experience with such devices? Good idea or bad? cheers, Graham ve3gtc ___ 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. -- Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do other things. ___ 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 Additive Phase Noise 10 MHz Amps
Discrete component designs using suitable silicon BJTs offer the lowest phase noise. Reworking some old designs to incorporate lower noise dc biasing (particularly collector/emitter current ) can significantly reduce close in PN. Bruce On Sunday, November 23, 2014 08:47:44 AM Bill wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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] LTE-lite pigtails
My unit didn't come with right-angle pigtails as shown in the doc (and Tom's photos). Did anyone else get straight connectors? ___ 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] rs-422 rs-232 to fast ethernet converter
Thanks Didier, Good suggestions and I have been considering something similar. cheers, Graham ve3gtc On 2014-11-23 13:26, Didier Juges wrote: Graham, There are a number of WiFi to serial modules like the one I use on my Thunderbolt monitor: The Microchip WiFly RN-XV-171. Once configured (typically using a PC), they will present a TCPIP port (TCP or UDP) from which you can get and send data directly to the serial port. Alternately, you can use Digi XBee modules that work like wireless RS232 isolators. I use the XSC Pro 900 MHz for a number of projects, including data loggers that are out of WiFi range. You can get well over a mile in open space with those. They are limited to 19200 bauds at the most. Didier KO4BB On November 22, 2014 4:47:15 PM CST, Graham planoph...@aei.ca wrote: I have been contemplating how I will would like to interface to the KS-23461 devices using rs-422. One option is a rs-422 to USB cable. Seems easy enough. But another option I keep stumbling across is a rs-422/rs-232 to fast ethernet such as: http://www.transition.com/TransitionNetworks/Products2/Family.aspx?Name=SDSFE3110-120 Frankly, I have no first hand knowledge or experience with these devices. First glance suggests that it might just be what I want - easy access to the KS-23461 ports through a connection to my local network without having a PC of some sort close by. So, any first hand experience with such devices? Good idea or bad? cheers, Graham ve3gtc ___ 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] Practical considerations making a lab standard with an LTE lite
Schomandl -- the company which made the first indirect synthesizers in the sixties in the past century -- used buried crystal oscillators as standard frequency source, 12meter deep in the companies yard in the Belfort Strasse in Munich, Bavaria Germany, ...Rohde Schwarz also had buried oscillators. I have one in California, where, the temperature at 10m deep is 15,784C° around the year, and measuring the frequency off set between wwvb's harmonic and the buried oscillator originally tuned to cca 3MHz, to the natural serial resonance of the crystal, by counting the beat -- to a harmonic of wwvb, cca 4217Hz , 364 358 801 pulses per day, as of Nov 2014, counter resets by wwvb daily, daily changes max ± 8 pulses, are to see, but a yearly decrement of 15 to 8 pulses per year, less per year in the last time is observable the system down thereis running since 1991. 73 KJ6UHN Alex On 11/23/2014 8:46 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 23 Nov 2014 14:45, Bob Camp kb...@n1k.org wrote: Hi If you have a basement in your house / building I do not. —and — it’s dry and reasonably draft free (no garage doors opening up from time to time) My lab is a room which is part of the garage! Just about everything is against me with this method, BUT you do give me an idea... You got me thinking about the possibility of actually mounting the TCXO burried in the ground! The temperature of that is not going to change very rapidly. FWIW, I know a guy that did work as an air conditioning engineer,, but now works for a company selling geothermal heating. He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. In a couple of years the temperature of the ground falls as the heat is extracted faster than it replenishes. So the efficiency falls off. I don't think that the TCXO would heat the ground faster than it dissipates away. Of course there would be some practical issues burying the TCXO, but those would not be insurmountable ones. I have no idea what depth might be needed. My wife thinks thinks I am a nutcase - that would only confirm it to her! Dave, G8WRB ___ 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] Practical considerations making a lab standard with an LTE lite
I've read about die-hard microwave hams burying their master oscillators for a long time . . . . On 11/23/2014 11:46 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 23 Nov 2014 14:45, Bob Camp kb...@n1k.org wrote: Hi If you have a basement in your house / building I do not. —and — it’s dry and reasonably draft free (no garage doors opening up from time to time) My lab is a room which is part of the garage! Just about everything is against me with this method, BUT you do give me an idea... You got me thinking about the possibility of actually mounting the TCXO burried in the ground! The temperature of that is not going to change very rapidly. FWIW, I know a guy that did work as an air conditioning engineer,, but now works for a company selling geothermal heating. He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. In a couple of years the temperature of the ground falls as the heat is extracted faster than it replenishes. So the efficiency falls off. I don't think that the TCXO would heat the ground faster than it dissipates away. Of course there would be some practical issues burying the TCXO, but those would not be insurmountable ones. I have no idea what depth might be needed. My wife thinks thinks I am a nutcase - that would only confirm it to her! Dave, G8WRB ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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] Practical considerations making a lab standard with an LTE lite
Interesting comment about the geothermal. I have to take continuing education courses in order to maintain my PE; one was in geothermal. Intuitively, great for cooling, even (especially!) in Florida. Intuitively, not so hot for heating, especially in PA, and especially with the price of natural gas plummeting. The guy who services our conventional AC and gas furnace was not very enthused, when I told him I was considering geothermal for the next cooling unit. He got a little more enthused when he found out I already have more pipe in the ground than I'd need (ft per ton of cooling capacity) and a several thousand gallon in-ground tank. Still not excited about it. I really appreciate your new data point. Shortly, I'll post response to all replies to my original post on this topic. For now, the bury it option might actually have use here. Jim On 11/23/2014 11:46 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 23 Nov 2014 14:45, Bob Camp kb...@n1k.org wrote: Hi If you have a basement in your house / building I do not. —and — it’s dry and reasonably draft free (no garage doors opening up from time to time) My lab is a room which is part of the garage! Just about everything is against me with this method, BUT you do give me an idea... You got me thinking about the possibility of actually mounting the TCXO burried in the ground! The temperature of that is not going to change very rapidly. FWIW, I know a guy that did work as an air conditioning engineer,, but now works for a company selling geothermal heating. He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. In a couple of years the temperature of the ground falls as the heat is extracted faster than it replenishes. So the efficiency falls off. I don't think that the TCXO would heat the ground faster than it dissipates away. Of course there would be some practical issues burying the TCXO, but those would not be insurmountable ones. I have no idea what depth might be needed. My wife thinks thinks I am a nutcase - that would only confirm it to her! Dave, G8WRB ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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] Practical considerations making a lab standard with an LTE lite
Did you use one-ply, two-ply, or three-ply TP? More seriously, your LTE-Lite differs in a couple of respects from the batch of production ones, or at least my example. Your TCXO seems to be in a metal package (shiny gold colour) and open to the air, if I'm interpreting the photo on your LTE-Lite page correctly (and also the photo that Said posted in his divide-by-two document). The production units have the TCXO in a solid black package, probably black epoxy, with a blob of RTV rubber on top. So the production units are probably already somewhat better shielded against drafts. (Thanks for doing the tests, particularly for those of us who can't do these tests ourselves. I can only watch the 1 PPS of the LTE-Lite wander with respect to the 1 PPS from my old Thunderbolt (Piezo oscillator), and look at the worst-case variation, but I have no way of knowing how much of the drift is due to each GPSDO). - Dave On Sun, Nov 23, 2014 at 11:24 AM, Tom Van Baak t...@leapsecond.com wrote: The short-term performance is 10x worse if you don't shield the TCXO from air, even if the ambient air is still. I suggested Said sell the product with some sort of engineered shield in place. Instead each of us will solve the problem in our own way; which is ok for a dev kit. For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. The insulation may be found in convenient rolls at many local stores. I used TP, which for this application is an acronym for Thermal Paper. /tvb ___ 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] LTE-lite pigtails
My first unit came with straight connectors. I can manage. On 11/23/2014 1:50 PM, Paul wrote: My unit didn't come with right-angle pigtails as shown in the doc (and Tom's photos). Did anyone else get straight connectors? ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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] Low Additive Phase Noise 10 MHz Amps
Bill, Check out the Ettus Octoclock. Its probably without competition at their $900 price point: https://www.ettus.com/content/files/Octoclock_Spec_Sheet.pdf Its very compact and quite useful. Is it the lowest noise amp ever built? No. But its state of the art for low-cost distribution of 1PPS and 10MHz in one single box. Bye, Said Sent From iPhone On Nov 23, 2014, at 8:47, Bill b...@hsmicrowave.com wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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] rs-422 rs-232 to fast ethernet converter
Didier has a good suggestion as to the serial to Wifi adapter. I may order one for my Z3801. Looking on Amazon, I see these two units that are more reasonably priced: http://www.amazon.com/Keynice-Ethernet-Intelligent-Communication-Wireless/dp/B00JTUVA0G/ref=pd_sim_sbs_e_1?ie=UTF8 http://www.amazon.com/Ethernet-Serial-RS232-RS485-Converter/dp/B00ATV2DX2/ref=pd_cp_pc_1 Joe Gray W5JG On Sun, Nov 23, 2014 at 11:59 AM, Graham planoph...@aei.ca wrote: Thanks Didier, Good suggestions and I have been considering something similar. cheers, Graham ve3gtc On 2014-11-23 13:26, Didier Juges wrote: Graham, There are a number of WiFi to serial modules like the one I use on my Thunderbolt monitor: The Microchip WiFly RN-XV-171. Once configured (typically using a PC), they will present a TCPIP port (TCP or UDP) from which you can get and send data directly to the serial port. Alternately, you can use Digi XBee modules that work like wireless RS232 isolators. I use the XSC Pro 900 MHz for a number of projects, including data loggers that are out of WiFi range. You can get well over a mile in open space with those. They are limited to 19200 bauds at the most. Didier KO4BB On November 22, 2014 4:47:15 PM CST, Graham planoph...@aei.ca wrote: I have been contemplating how I will would like to interface to the KS-23461 devices using rs-422. One option is a rs-422 to USB cable. Seems easy enough. But another option I keep stumbling across is a rs-422/rs-232 to fast ethernet such as: http://www.transition.com/TransitionNetworks/Products2/Family.aspx?Name=SDSFE3110-120 Frankly, I have no first hand knowledge or experience with these devices. First glance suggests that it might just be what I want - easy access to the KS-23461 ports through a connection to my local network without having a PC of some sort close by. So, any first hand experience with such devices? Good idea or bad? cheers, Graham ve3gtc ___ 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] Practical considerations making a lab standard with an LTE lite
All: I appreciate all the responses to my post earlier today. Very informative. First: DownEast Microwave sells a nice kit for distributing 10 MHz. Specs are on their website, but basically, one in, four out -- each individually buffered and filtered. Second: I will use the 20 MHz from the LTE-Lite to lock a 100Mhz TCXO which will be the LO for a high performance 2meter amateur software defined radio. (OpenHPSDR.org for info on the SDR) I may multiply it to help with some of the microwave LOs. It will also use the 20 Mhz to lock a 1GHz TXCO to be multiplied for microwave LOs. Third: I will have three of the LTE-Light units. The first will feed some LOs as described above, and the synthesized 10 MHz output will be my lab frequency standard. The lab is in a cinder block room off the basement, with 2 of foam insulation under 2 inches of concrete which is the floor for a covered porch above. I'd never thought of it, but the put it on the floor next to a brick wall idea fits here. Actually, I can put it next to 2 buried brick walls, and will surround it with cinder block on the remaining sides. Can probably cover it with a few 12x12 paver stones. NOW, this involves drilling a hole through cinder block and drywall between the office/ham shack and the lab. Would rather not, but have to anyway. I have been informed that the fan noise from the ham shack gigabit ethernet switch will become politically unacceptable in about 72 hours. (Office/ham shack share a guest bedroom.) I would like to get 1E-10 or 1E-11 accuracy out of this setup. Thanks for this suggestion! Fourth: The second unit will be in a building at the base of my antenna tower, about 350 feet from the house. This building is above ground, and will be allowed to swing from 45F to 80F over the course of the year. Hence my interest in insulating and heating. I might consider putting something in the ground here, the problem would be access for servicing I would like to get 1E-10 or 1E-11 accuracy out of this unit. Considered shipping 10 MHz in coax out from the house, would rather not, and would like some redundancy, anyway. Fifth: I get that the /efc/ vs. /temp/ relationship is very complex and accept that trying to characterize it is not worth the effort. Thanks for this bit of information. Sixth: My third LTE-Lite will drive a 10MHz reference for a mobile (rover) microwave setup, providing the reference for a bunch of GHz LOs. This station will see motion, and temperature variation. Ultra low power will not be a concern, so heaters are acceptable. I would be happy with 1E-9 accuracy out of this unit. That translates into 10Hz frequency error at 10 GHz. This kind of frequency accuracy has been demonstrated to provide 3+db improvement in the ability to detect weak signals -- very significant for microwave weak signal work. Finally: I have pondered all the suggestions about measuring output impedance, etc. For now, I have decided to default to Said's expertise with the units and will use one of his suggested circuits as buffers. Hopefully, these will be on a board inside the HAMMOND box with the LTE-Lite. That buffer will drive one of the MMICs to provide additional power to drive a filter and then output to the distribution amplifier. I will continue to look for a better idea from one of you smarter than me. Thanks again for all the insight and ideas. You guys type and I learn. 73, Jim wb4...@amsat.org On 11/23/2014 4:46 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: I would like to make a unit with multiple 10 MHz 50 Ohm outputs to feed my various bits of test equipment. I am thinking about some practical considerations. 1) It would be great if there was a circuit published which can give 50 Ohn output impedance from a 12-15 power supply, which a) Doesn't load the TCXO b) Doesn't degrade the phase noise. c) Powered the LTE lite. Ideally one for both 10 20 MHz crystals. Better still if there was a PCB available. 2) How should I mount the components? My preference would be a metal box with * IEC mains socket * antenna input socket * 9-pin D for reading dats * 15 BNC's outputs With a power amplifier to provide the output for 15 sockets, some ventilation possibly requiring a small amount of forced air cooling would be needed. But given the TCXOs sensitivity to temperature changes, I don't know whether it might be preferable to mount the LTE lite in its own box without any power supplies in it - perhaps with some thermally insulting material around the LTE lite so the crystal doesn't experience any fast temperature changes. Then have the power hungry bits completely separately. I don't have a particularly big lab, so wherever I mount the LTE lite, the temperature is going to change with the air conditioning unit blows hot or cold There are fairly large temperature changes when I am not using the lab, as I don't run the air conditioning unit
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
Hi guys, this is the kind of lively discussion I was hoping for! I enjoyed this. Some comments (these are my opinions only): * Thanks much for Tom publishing the plots, and spending a lot(!) of time evaluating and helping improve the units significantly. Tom's unit was a pre-production unit. We added RTV (some units black, some a combo) to the TCXO production units based on his suggestion of the successful TP modification. The RTV will help keep airflow away, but additional shielding will help even more. * There is a point where thermally stabilizing the unit does not help anymore. I suspect that point is reached shortly before burying the unit 50 meters underground :) At the point of diminishing marginal returns the GPS and loop noise will be larger than the thermally induced phase offsets. Also local heating from the GPS receiver (which is not constant) will swamp external thermal effects at some point. For us in our lab, the point of diminishing returns is reached when we simply slide the unit into its ESD packaging, then put some pink ESD padding on top of it. With that simple shielding we can get ADEV at 5x to 8x its rated 1ppb performance out of most units. * Temperature changes are typically not the problem with TCXOs, simple airflow and convection turbulence is what causes most of the phase drift problems. As shown by Tom simply putting a layer of TP on top of the unit made a huge difference in stability by keeping convective flow away from the TCXO, while it probably did nothing for temperature insulation. These convective flows are very fast and high-frequency so inside the GPS loop time constant, whereas temp changes are usually easy to low-pass dampen to the point that the GPS loop will hide them. * Actively heating the units' enclosure to some stable temperature is counter-productive in my opinion for two reasons: first higher temperatures cause convective airflow inside the enclosure. We want as little convective flow as possible. Second CMOS slows down at higher temperatures, and noise levels go up with temperature. As mentioned before temperature changes (other than instant changes such as when the sun almost sudden hits the enclosure) usually are easily low-pass filtered to be slower than the GPS loop time constant which is below a couple 100 seconds, so keeping the enclosure at some high temperature is probably going to make things worse. There are other items to consider such as the AT-cut TCXO crystal probably has its most stable operating point at around 25C, and the lifetime MTBF of electronics typically gets cut in half with every 10C Degree increase in temperature. * The 10MHz units have a different RF output than the 20MHz units. The 20MHz units have a 50 Ohms series-terminated and buffered RF output, while the 10MHz units have the TCXO output drive the MMCX connector directly without series impedance matching. Both drive the line with 3.0V CMOS levels. This means the cable on the 10MHz unit should be kept as short as possible, and that impedance matching for maximum power-transfer is not required nor desired. The suggestion that Charles made for checking the impedance by progressively loading the output more and more is valid for Sine Wave outputs, but not for CMOS outputs as implemented on the LTE Lite. One issue is that the TCXO is driving a 1.8V CMOS input through a capacitive voltage divider, and if you load the TCXO so much that its output voltage goes to 1/2 the no-load voltage then the input of the processor will likely not get enough voltage range to operate properly. I mentioned 1M Ohms input impedance simply for convenience as it is a standard input impedance as Charles mentions. You can significantly reduce that impedance since the 10MHz TCXO can drive a handful of mA no problem, and the 20MHz buffered output can drive 20mA or more. This means a 1K Ohms load is also no issue as it would load the output only with 3mA, however(!) the more you load the CMOS output the more heating will happen in the 3.0V linear regulator close to the TCXO and inside the 10MHz DIP-14 TCXO. This will cause load-induced instability. The best input for the LTE-Lite output is simply a 3.3V or 5V powered CMOS gate. No input termination resistance required. Cable lengths should be kept short (less than a foot) to prevent ringing and loading the TCXO output for more than a couple of nanoseconds as the edges traverse into the coax. I like to put a weak pull-down of 470K to 1M on those CMOS gate inputs so the input does not float when its not connected to anything. There is absolutely no need to load down the output with 100 Ohms, 1K, or even 10K. For CMOS inputs, the only thing that makes a difference in phase noise seems to be the rise/fall time and voltage swing. The faster swing and higher voltage the better. Loading down the output will reduce this
[time-nuts] Surplus OCXO’s
Ok, this got a bit tangled with various email addresses linked to here and there. Let’s see if it works better this way. Hi On Nov 23, 2014, at 1:04 AM, Perry Sandeen sandee...@yahoo.com wrote: List, Wrote: Surplus OCXO’s are well … surplus. A significant percentage of the OCXO’s I’ve seen on the surplus marked are pulls off boards and are busted. I’ve bought quite a few from “tested / guaranteed / 100% good / perfect buy” sellers and found issues with then when you carefully test them. Well that is depressing as all get out. So some questions. What were the issues you found when carefully tested? There were a range of issues from “no output / runaway heater” to “output goes away after a week” to “ADEV well out of spec”. Were those issues reasonably repairable? Some of the first order stuff was. None of them really came up to full performance. If an overseas vender has an OCXO that’s still attached to a board, is it likely to be OK? That depends a lot on things you can’t possibly know. Was that batch of OCXO’s damaged when they were installed, did the board blow up , …. Was your *good yield* worth the low price and sorting? (Ignoring your time spent issue.) At 20% after repair, not to me. Others have had much better luck. The vender Fluke1 appears to do some extensive testing of his OCXO’s. Would he be a better source than others? I’ve had better luck with him than with others. I have (rarely) received various things from him over the years that did not work 100%. He has *always* been helpful in those cases. His prices are higher than some others, that may reflect the true cost of good parts compared to un-sorted parts. My questions are based that one can get 10811’s on a board here in the USA for $125 or the later model new for $100 from china. Specifically on a 10811, you want to be sure it didn’t go under water. It’s an un-sealed unit. Bob TIA. Regards, Perrier ___ 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 Additive Phase Noise 10 MHz Amps
Hi For any “real world” source being distributed, simple high speed CMOS buffers will not add enough noise to matter at 10 MHz. That of course also assumes that the target gear is the normal bunch of instruments that we all play with. Bob On Nov 23, 2014, at 11:47 AM, Bill b...@hsmicrowave.com wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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] Practical considerations making a lab standard with an LTE lite
Hi If your target frequency error is in the 1x10^-10 to the “hopefully 1x10^-11” range, You should consider your very requirements carefully. I tossed up some frequency plots of the KS boxes and of the Z3801 a while back. They are OCXO based boxes running in a very good thermal environment. Their OCXO’s ADEV is roughly 1x10^-12 at 1 to 10 seconds. That compares directly to the TCXO’s apparent ADEV posted by Tom earlier at 5x10^-11 in the 1 to 10 second region. The OCXO based parts (with a very loose interpretation of 1x10^-11 frequency accuracy) do not hit +/- 1x10^-11 frequency accuracy. If the plots are to far back to dig up, I can re-post them. They will hit a 1x10^-10 frequency accuracy limit without any quibbling over the definition of the spec. The frequency accuracy of a TCXO based part is not going to measure up to an OCXO based part. That’s not because the TCXO part is in some way flawed, it’s just the way things work on a GPSDO. If you are going with a TCXO, concrete bunker construction is not needed. With an OCXO based part, it just might help a bit. This may be a bit counter intuitive. It’s a function of where the (much better) ADEV of the OCXO intersects the (constant slope) ADEV of the GPS receiver. The control loop on the OCXO based part will be running at a *much* longer time constant. If the OCXO ADEV is 10X better, it will be 10X longer. If it’s 100X better it will be 100X longer. In both cases (TCXO and OCXO) the ADEV at 1 or even 10 seconds will not be improved by thermal this or that , once drafts are eliminated. The filter will still track where it needs to track. If the OCXO is running a filter out at a thousand seconds, you will *will* see slow thermal variations. The TCXO based part’s output running at (say) 10 seconds will not see the same variations, they will be corrected out by the GPS before they hit the output. — Why tie these things together? Where you wind up depends very much on where you are headed. Starting with the right gear for the application will matter in the end. Putting a lot of effort into a project without considering the ultimate goal may not be as economical as it could otherwise be. Bob On Nov 23, 2014, at 3:04 PM, Jim Sanford wb4...@wb4gcs.org wrote: All: I appreciate all the responses to my post earlier today. Very informative. First: DownEast Microwave sells a nice kit for distributing 10 MHz. Specs are on their website, but basically, one in, four out -- each individually buffered and filtered. Second: I will use the 20 MHz from the LTE-Lite to lock a 100Mhz TCXO which will be the LO for a high performance 2meter amateur software defined radio. (OpenHPSDR.org for info on the SDR) I may multiply it to help with some of the microwave LOs. It will also use the 20 Mhz to lock a 1GHz TXCO to be multiplied for microwave LOs. Third: I will have three of the LTE-Light units. The first will feed some LOs as described above, and the synthesized 10 MHz output will be my lab frequency standard. The lab is in a cinder block room off the basement, with 2 of foam insulation under 2 inches of concrete which is the floor for a covered porch above. I'd never thought of it, but the put it on the floor next to a brick wall idea fits here. Actually, I can put it next to 2 buried brick walls, and will surround it with cinder block on the remaining sides. Can probably cover it with a few 12x12 paver stones. NOW, this involves drilling a hole through cinder block and drywall between the office/ham shack and the lab. Would rather not, but have to anyway. I have been informed that the fan noise from the ham shack gigabit ethernet switch will become politically unacceptable in about 72 hours. (Office/ham shack share a guest bedroom.) I would like to get 1E-10 or 1E-11 accuracy out of this setup. Thanks for this suggestion! Fourth: The second unit will be in a building at the base of my antenna tower, about 350 feet from the house. This building is above ground, and will be allowed to swing from 45F to 80F over the course of the year. Hence my interest in insulating and heating. I might consider putting something in the ground here, the problem would be access for servicing I would like to get 1E-10 or 1E-11 accuracy out of this unit. Considered shipping 10 MHz in coax out from the house, would rather not, and would like some redundancy, anyway. Fifth: I get that the /efc/ vs. /temp/ relationship is very complex and accept that trying to characterize it is not worth the effort. Thanks for this bit of information. Sixth: My third LTE-Lite will drive a 10MHz reference for a mobile (rover) microwave setup, providing the reference for a bunch of GHz LOs. This station will see motion, and temperature variation. Ultra low power will not be a concern, so heaters are acceptable. I would be happy with 1E-9 accuracy
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
On 23 Nov 2014 16:25, Tom Van Baak t...@leapsecond.com wrote: For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. Tom, What plots are with and without the thermal paper? I see several graphs, but don't know what is under what conditions. The second graph shows something fairly significant happening at 300 s. Is that where you removed the TP? Dave ___ 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] Practical considerations making a lab standard with an LTE lite
Hi Well the answer is obvious:) You simply need to turn on the air-conditioning full blast for more months of the summer in … ummm ….. e …. Denmark … hmmm….. Heat only or cool only systems seem to be more practical when the heat sink is a flowing body of water or an ocean. Unfortunately those seem to also run up the price of adjacent real estate. Moving bodies of water also aren’t very good for stabilizing temperature on a frequency source. The same thing is true of a hole in the ground that goes above or below the level of ground water over the course of the year. If you drill a hole, there is indeed a wrong depth to pick. It might be interesting to see how deep you need to go for stable ground water temps. Around here the top layer of ground water was rain last week or last month. Bob On Nov 23, 2014, at 1:07 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message canx10hcaob-5gysbr7sdxwl7dyh7qubmhxwmi9xdrcf3mdm...@mail.gmail.com , Dr. David Kirkby (Kirkby Microwave Ltd) writes: Geothermal means you drill at least 50m (Iceland) or more likely half a kilometer down, in order to harvest water at near boiling point from the Earths geological heat-sources (mostly uranium decay). Sorry. What he installs is pipes in the ground in residential or industrial sites. Basically he says they work initially, but performance drops dramatically over a couple of years. That is not geothermal then, and yes, a LOT of those systems are badly underdimensioned. I've been researching this topic intensively because my new house will be heated that way. My conclusion, based on reading a lot of reports, is that there is no credible way to predict the performance. The wetter your soil the better, but that's about it. I'm going to overprovision by a factor two to be on the safe side, afterall it only costs EUR7 for each extra meter of pipe. -- 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] Practical considerations making a lab standard with an LTE lite
Hi There are two plots with activity changing at 300 seconds. The second plot (purple) is the removal of the paper at 300 seconds. The fourth plot (red) is the addition of the paper at 300 seconds. The last plot (green and blue) is ADEV with and without the paper. Blue is ADEV with paper. Green is ADEV without paper. The second to last plot demonstrates the unit meeting 1x10^-9 (peak to peak) frequency stability with the paper over a 1,000 second test. It shows it doing about 5X worse on frequency stability over the same period without the paper. Yes, that’s all with 1 second averaging. Changing the averaging would impact each of the results. It should change their ratio. Again back to the basic question: frequency over what period? Go to a 24 hour average and the results should be terrific. In some systems, that’s a useful number (I guess….). I rarely see people set their counters to an 86,000 second gate time :) Bob On Nov 23, 2014, at 4:42 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 23 Nov 2014 16:25, Tom Van Baak t...@leapsecond.com wrote: For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. Tom, What plots are with and without the thermal paper? I see several graphs, but don't know what is under what conditions. The second graph shows something fairly significant happening at 300 s. Is that where you removed the TP? Dave ___ 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] LTE-lite pigtails
Paul Mine came with right angles. It does make for a nicer arrangement. Regards Paul WB8TSL On Sun, Nov 23, 2014 at 2:26 PM, Jim Sanford wb4...@wb4gcs.org wrote: My first unit came with straight connectors. I can manage. On 11/23/2014 1:50 PM, Paul wrote: My unit didn't come with right-angle pigtails as shown in the doc (and Tom's photos). Did anyone else get straight connectors? ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.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. ___ 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] Practical considerations making a lab standard with an LTE lite
Tom, From the looks of the plots these may be from the first proto unit with early software no? Also was this with the indoor GPS antenna setup? The production units with outdoor or windowed' antenna should have significantly improved average performance from the first unit and its early GPS and GPSDO firmware versions. Bye, Said Sent From iPhone On Nov 23, 2014, at 14:18, Bob Camp kb...@n1k.org wrote: Hi There are two plots with activity changing at 300 seconds. The second plot (purple) is the removal of the paper at 300 seconds. The fourth plot (red) is the addition of the paper at 300 seconds. The last plot (green and blue) is ADEV with and without the paper. Blue is ADEV with paper. Green is ADEV without paper. The second to last plot demonstrates the unit meeting 1x10^-9 (peak to peak) frequency stability with the paper over a 1,000 second test. It shows it doing about 5X worse on frequency stability over the same period without the paper. Yes, that’s all with 1 second averaging. Changing the averaging would impact each of the results. It should change their ratio. Again back to the basic question: frequency over what period? Go to a 24 hour average and the results should be terrific. In some systems, that’s a useful number (I guess….). I rarely see people set their counters to an 86,000 second gate time :) Bob On Nov 23, 2014, at 4:42 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 23 Nov 2014 16:25, Tom Van Baak t...@leapsecond.com wrote: For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. Tom, What plots are with and without the thermal paper? I see several graphs, but don't know what is under what conditions. The second graph shows something fairly significant happening at 300 s. Is that where you removed the TP? Dave ___ 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] Practical considerations making a lab standard with an LTE lite
Hi A lot of these parts are designed for use in a system environment rather than sitting out on a bench. That’s as true of the KS boxes (forced air cooling) as it is of the LTE’s. In 90% (and likely 99.9%) of the places a TCXO gets used, it’s packed tight in with a bunch of other stuff. Not only is there no air movement, there might not be much air. A cell phone is a good example of this sort of assembly. Other battery powered portable gear fit this same general model, but possibly not to the same degree of “cram it in. Yes, we love our big rack mounted boxes full of this or that. They are useful. The TCXO guys would go broke quickly if that was the market they focused their main efforts on. Big Morion 2” x 2” x 1” OCXO’s, yes those are targeted more at big rack mount this or that. Different market focus for different products. It’s not a one size fits all world. Indeed, adapting a TCXO to a bench environment is something that you need to do. A nice fluffy cotton towel works quite well. Yes, that’s a 1970’s solution to the problem. Most TCXO’s were bigger back then. The issue has been around “for a while”. It’s actually not a bad thing to keep handy when testing OCXO’s. If they don’t work you can always use it to cry into …:) Bob On Nov 23, 2014, at 11:24 AM, Tom Van Baak t...@leapsecond.com wrote: The short-term performance is 10x worse if you don't shield the TCXO from air, even if the ambient air is still. I suggested Said sell the product with some sort of engineered shield in place. Instead each of us will solve the problem in our own way; which is ok for a dev kit. For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. The insulation may be found in convenient rolls at many local stores. I used TP, which for this application is an acronym for Thermal Paper. /tvb ___ 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] Practical considerations making a lab standard with an LTE lite
Hi Actually that was Bob trying to explain Tom’s plots simply from looking at them. I *think* I got it right, but it’s Tom’s data and his LTE part. Others have commented that Tom’s part looks different than theirs. Maybe Tom needs a Microsoft Windows Update on his GPSDO firmware :) For some reason the very thought of Microsoft getting involved in something like that makes me shudder… Bob On Nov 23, 2014, at 5:33 PM, Said Jackson via time-nuts time-nuts@febo.com wrote: Tom, From the looks of the plots these may be from the first proto unit with early software no? Also was this with the indoor GPS antenna setup? The production units with outdoor or windowed' antenna should have significantly improved average performance from the first unit and its early GPS and GPSDO firmware versions. Bye, Said Sent From iPhone On Nov 23, 2014, at 14:18, Bob Camp kb...@n1k.org wrote: Hi There are two plots with activity changing at 300 seconds. The second plot (purple) is the removal of the paper at 300 seconds. The fourth plot (red) is the addition of the paper at 300 seconds. The last plot (green and blue) is ADEV with and without the paper. Blue is ADEV with paper. Green is ADEV without paper. The second to last plot demonstrates the unit meeting 1x10^-9 (peak to peak) frequency stability with the paper over a 1,000 second test. It shows it doing about 5X worse on frequency stability over the same period without the paper. Yes, that’s all with 1 second averaging. Changing the averaging would impact each of the results. It should change their ratio. Again back to the basic question: frequency over what period? Go to a 24 hour average and the results should be terrific. In some systems, that’s a useful number (I guess….). I rarely see people set their counters to an 86,000 second gate time :) Bob On Nov 23, 2014, at 4:42 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 23 Nov 2014 16:25, Tom Van Baak t...@leapsecond.com wrote: For plots and photos showing performance with, and without, and with insulation see: http://leapsecond.com/pages/LTE-Lite/ The difference is dramatic, especially if you are used to working with OCXO where this sort of effect does not occur. Tom, What plots are with and without the thermal paper? I see several graphs, but don't know what is under what conditions. The second graph shows something fairly significant happening at 300 s. Is that where you removed the TP? Dave ___ 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. ___ 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] Practical considerations making a lab standard with an LTE lite
by us in central California, we get 1kW/h square meter average around the year, the south even more, el Cajon will have today +29C° in the afternoon as of 23 of November 2014 73 Alex On 11/23/2014 9:49 AM, Poul-Henning Kamp wrote: In message canx10hb0kdrnaayzgvm1gkduj7gklth0acdxczg894hxbus...@mail.gmail.com , Dr. David Kirkby (Kirkby Microwave Ltd) writes: He installs ground source heat pumps for the geothermal energy. He says that they actually work quite poorly in many cases. There is a BIG difference between geothermal and ground heating. Geothermal means you drill at least 50m (Iceland) or more likely half a kilometer down, in order to harvest water at near boiling point from the Earths geological heat-sources (mostly uranium decay). Extracting more energy than available just means the temperature drops temporarily. It will increase again once you reduce the pump rate. Horizontal ground heat means that you are harvesting sunshine accumulated in the top one meter of the soil. Much of the energy is harvested from freezing the water around the pipe thus pulling out the relatively high melting energy of water. If you extract more energy than you deposit sunshine, you end up freezing a larger and larger volume of water/soil around the pipe and your compressor will eat a lot of electricity. In practice it looks like this: http://ing.dk/artikel/varmepumpe-mareridt-jordslange-var-dybfrossen-i-maj-113176 (The two pictures show the same pipe, with and without frozen ground.) Finally there is vertial ground heat where you drill down only about 40-80 meter, tapping heat mostly from ground water resources.Most places the ground water doesn't move fast enough to deliver the amounts of energy extracted, and over time the source returns unusably low temperature and must be abandonned. Typically after 25-30 years. ___ 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] ocxo
Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham d...@montana.com wrote: So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is out of tolerance. All self tests pass with flying colors, autocal works as well. So the best parts are OK. Does anyone: 1) have a spare Isotemp OCXO36-53 10.000 MHz p/n 6-00051? 2) know the specs, ie the input voltage/current and the control voltage span and direction? pinout? I have some Morion mv-89's and could easily cobble one in if it will work. Apparently a correct oscillator must be in place to use an external source, if I read the manual right. 3) do we have a source for the schematics for the SR 620? The FTS 4060 is up, pumpin' and firmly locked. At least for now. That dealer was not lyin' Much thanks to all of you. The adventure continues -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850
Re: [time-nuts] ocxo
Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham d...@montana.com wrote: So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is out of tolerance. All self tests pass with flying colors, autocal works as well. So the best parts are OK. Does anyone: 1) have a spare Isotemp OCXO36-53 10.000 MHz p/n 6-00051? 2) know the specs, ie the input voltage/current and the control voltage span and direction? pinout? I have some Morion mv-89's and could easily cobble one in if it will work. Apparently a correct oscillator must be in place to use an external source, if I read the manual right. 3) do we have a source for the schematics for the SR 620? The FTS 4060 is up, pumpin' and firmly locked. At least for now. That dealer was not lyin'
Re: [time-nuts] ocxo
No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham d...@montana.com wrote: So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is out of tolerance. All self tests pass with flying colors, autocal works as well. So the best parts are OK. Does anyone: 1) have a spare Isotemp OCXO36-53 10.000 MHz p/n 6-00051? 2) know the specs, ie the input voltage/current and the control voltage span and direction? pinout? I have some Morion mv-89's and could easily cobble
Re: [time-nuts] ocxo
Did we answer the q? about schematics? All of SRS's products have their block diagram and parts list with a detailed circuit description in their user manual. Sneak preview: its all resistors. NS On Sun, Nov 23, 2014 at 4:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham
Re: [time-nuts] ocxo
Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace what you have. Bob On Nov 21, 2014, at 6:59 PM, Don Latham d...@montana.com wrote: So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The ocxo is out of tolerance. All self tests pass with flying
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
A Hint about avoiding convective cell heat transfer, If you keep the spacing between two planes less than 5/16 then you will be unlikely to have convection cells forming. The stationary air is a good insulator but thermal radiation will be the dominant heat transfer process. This is true for double glazing, katharometers and generally all devices. The suppression of turbulent heat transfer may provide more insulation but also less noise and instability. So it may be a good idea to use a relatively close fitting box with thick walls. Cheers, Neville Michie On 23/11/2014, at 11:37 PM, Charles Steinmetz wrote: Dave wrote But given the TCXOs sensitivity to temperature changes, I don't know whether it might be preferable to mount the LTE lite in its own box without any power supplies in it - perhaps with some thermally insulting material around the LTE lite so the crystal doesn't experience any fast temperature changes. First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). Use thermally insulating standoffs (teflon or nylon, with no metal through fasteners) to get the board in the middle of the volume of the box. Use a box a bit larger than you'd first think, so there is at least 1 of air on all 6 sides of the LTE board. Do NOT mount any part of the LTE board (connectors, etc.) directly to the box walls -- use pigtails for all connections. Do NOT use any insulation between the LTE and the box walls other than the 1+ of air. The mounting described above will add substantial thermal capacitance to the LTE board (good) without adding significant thermal resistance (bad). For further discussions of this issue, search the list archives for thermal capacitance and thermal mass. Now, mount the cast box (plus any thermal mass you add to it -- see below) so that IT is thermally isolated from the overall enclosure (or, if it sits out in the open, thermally isolated from anything solid). The air space in the enclosure isolates the oscillator from the cast box and the box is sufficiently massive that its temperature cannot change nearly as fast as ambient. The thermal mass of the cast box can be adjusted by adding thermal mass to it as desired. The goal is for the box temperature to change only by changes in ambient AIR temperature, and the LTE board to change only by changes in the AIR temperature inside the cast box. This integrates any changes to the LTE board temperature with a very long time constant, which allows the GPS discipline to track and cancel the temperature changes. (If you mount an ovenized oscillator this same way, it integrates any changes to the OCXO temperature so that the oven control loop can track and cancel any changes to the crystal temperature.) You can, of course, improve things even further by making sure the ambient air temperature surrounding the cast box changes slowly, or not at all. But the technique described above can be counted on to reduce thermal effects in most OCXOs or GPSDOs to better (often much better) than the 1e-13 level unless the ambient temperature changes MUCH more and MUCH faster than any change we wouild consider normal for a living space. This is true whether the cast box is mounted out in the open, or inside an overall enclosure with other electronics. Best regards, Charles ___ 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] Practical considerations making a lab standard with an LTE lite
Hi I believe that if you go back a few years in the archives, you will find a thread that ultimately stops with a swimming pool full of mercury. Needless to say, we’re been down this road once or twice before. Bob On Nov 23, 2014, at 7:59 PM, Neville Michie namic...@gmail.com wrote: A Hint about avoiding convective cell heat transfer, If you keep the spacing between two planes less than 5/16 then you will be unlikely to have convection cells forming. The stationary air is a good insulator but thermal radiation will be the dominant heat transfer process. This is true for double glazing, katharometers and generally all devices. The suppression of turbulent heat transfer may provide more insulation but also less noise and instability. So it may be a good idea to use a relatively close fitting box with thick walls. Cheers, Neville Michie On 23/11/2014, at 11:37 PM, Charles Steinmetz wrote: Dave wrote But given the TCXOs sensitivity to temperature changes, I don't know whether it might be preferable to mount the LTE lite in its own box without any power supplies in it - perhaps with some thermally insulting material around the LTE lite so the crystal doesn't experience any fast temperature changes. First, mount the LTE in a cast aluminum box (not thin sheet metal, something with some heft). Use thermally insulating standoffs (teflon or nylon, with no metal through fasteners) to get the board in the middle of the volume of the box. Use a box a bit larger than you'd first think, so there is at least 1 of air on all 6 sides of the LTE board. Do NOT mount any part of the LTE board (connectors, etc.) directly to the box walls -- use pigtails for all connections. Do NOT use any insulation between the LTE and the box walls other than the 1+ of air. The mounting described above will add substantial thermal capacitance to the LTE board (good) without adding significant thermal resistance (bad). For further discussions of this issue, search the list archives for thermal capacitance and thermal mass. Now, mount the cast box (plus any thermal mass you add to it -- see below) so that IT is thermally isolated from the overall enclosure (or, if it sits out in the open, thermally isolated from anything solid). The air space in the enclosure isolates the oscillator from the cast box and the box is sufficiently massive that its temperature cannot change nearly as fast as ambient. The thermal mass of the cast box can be adjusted by adding thermal mass to it as desired. The goal is for the box temperature to change only by changes in ambient AIR temperature, and the LTE board to change only by changes in the AIR temperature inside the cast box. This integrates any changes to the LTE board temperature with a very long time constant, which allows the GPS discipline to track and cancel the temperature changes. (If you mount an ovenized oscillator this same way, it integrates any changes to the OCXO temperature so that the oven control loop can track and cancel any changes to the crystal temperature.) You can, of course, improve things even further by making sure the ambient air temperature surrounding the cast box changes slowly, or not at all. But the technique described above can be counted on to reduce thermal effects in most OCXOs or GPSDOs to better (often much better) than the 1e-13 level unless the ambient temperature changes MUCH more and MUCH faster than any change we wouild consider normal for a living space. This is true whether the cast box is mounted out in the open, or inside an overall enclosure with other electronics. Best regards, Charles ___ 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] Practical considerations making a lab standard with an LTE lite
Said wrote: The 10MHz units have a different RF output than the 20MHz units. The 20MHz units have a 50 Ohms series-terminated and buffered RF output, while the 10MHz units have the TCXO output drive the MMCX connector directly without series impedance matching. Both drive the line with 3.0V CMOS levels. This means the cable on the 10MHz unit should be kept as short as possible, and that impedance matching for maximum power-transfer is not required nor desired. The suggestion that Charles made for checking the impedance by progressively loading the output more and more is valid for Sine Wave outputs, but not for CMOS outputs as implemented on the LTE Lite. Absolutely correct -- I did not anticipate that anyone would make unbuffered logic levels available to the external world. In that case, I'd put a logic-level line driver immediately at the unit (by immediately, I mean with a small breakout card that plugs directly onto the LTE's MMCX connector with no intervening cable). For example, all 6 outputs of an HC14 or AC14 hex inverter connected in parallel, or a dedicated line driver chip like an HC365/366 or AC240/244/540/541. The buffer should be inside the enclosure with the LTE, and I would also add a T-network filter to convert the logic-level square wave into a sine wave. This would confine all of the fast logic transitions inside the shielded box, where they can do the least mischief. For the T-network, I like 10uH/50.5pF/10uH, others like 1.5uH/310pF/1.5uH. Both draw ~ +/- 35mA from a 5v logic output. Make sure your buffer can supply this current, and feed the T-network through 10nF and 50 ohms in series. You'll get a 1Vrms (13dBm) sine wave into 50 ohms (675mVrms with 3v logic). H3 is down 40dBc with the 1.5uH network and 60dBc with the 10uH network. [Note that the apparent source impedance is 50 ohms, so the open-circuit voltage is more than double.] Best regards, Charles ___ 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] ocxo
Schematics in KO4BB magnificent storehouse. Neil Schroeder Did we answer the q? about schematics? All of SRS's products have their block diagram and parts list with a detailed circuit description in their user manual. Sneak preview: its all resistors. NS On Sun, Nov 23, 2014 at 4:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the built-in phase lock to do this. Anyhow, autocal calibrates everything except, guess what, the 10 mhz source. Thats done separately. So a bootup self check shows OK even if the frequency standard is way off. Onward and upward. Don Bob Camp Hi I believe that the SR620 uses a “true” 10 MHz OCXO. I would be careful using a 5 MHz doubled to 10 OCXO. The counter may or may not be happy with sub-harmonic induced jitter. Best bet at the specs: +12V power 0-5V EFC Sine wave out +7dbm +/- 5x10^-9 0 to 70C Pinout - trace
Re: [time-nuts] ocxo
From the manual, I infer the dac is 10 bit. ( 4096 max count) Span is 5 volts. I've connected the gpsdo and the clock error light does not light; I'm assuming the morion is locking to the gpsdo OK. I do have the original, was going to open it up sometime. I suspect something wrong with the heater. Should just start by measuring current into + and - 15 volts. I think that Said's device could just be put inside the SR fb, and convert the external input bnc to the gps antenna. No sweat. Even the low end clock osc would work quite well, no fancy ocxo needed. SR can also be used with internal clock if needed. The dac value is saved so the internal osc is automatically calibrated by this technique. I'm really impressed by this box! A lot of thought went into it. Don Bob Camp Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer term. Probably has a long time constant on the
Re: [time-nuts] ocxo
No but a little math based on your ocxo's range can help... but measuring it in person does give you the best numbers. More precision and more bits WON'T hurt here and the application notes from the leading crystal makers suggest a DAC front ended by a precision op amp with and that the xo be followed by a buffer. So I took the nuclear option: http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf My Wenzels don't have a reference out and neither do any of my VCXOs, but my $30 Vectron from Ebay does - so my circuit for it is modified to accept its reference voltage (its also plugged into an ADF4001 now) NS On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp kb...@n1k.org wrote: Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little research has me thinking I can easily adapt a morion. I can try it at least by starting with the morion on an external power supply and patching the output and control voltages in to the sr. The sr620 has a control circuit which apparently accomplishes your suggestions; they claim to use the internal oscillator for short term and lock it to a supplied external source for longer
Re: [time-nuts] Practical considerations making a lab standard with an LTE lite
Hi Jim: It turns out that ground water that's being pumped is very similar to pumping oil. It's a limited resource. There's a web page showing the GRACE satellite maps of California and that we are running out of ground water. This isn't the page, but gives the idea: http://www.cnyo.org/2014/08/19/nasa-space-place-droughts-floods-and-the-earths-gravity-by-the-grace-of-nasa/ So depending on ground water as a stable heat sink may no longer be an option as wells go dry. It's been many years since the local water company has quit installing new meters. Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Jim Lux wrote: On 11/23/14, 11:15 AM, Alex Pummer wrote: by us in central California, we get 1kW/h square meter average around the year, the south even more, el Cajon will have today +29C° in the afternoon as of 23 of November 2014 I suspect more like the insolation peaks at 1kW/square meter or a bit more, the average over a day is somewhat less. At JPL we have a weather station on line that displays this and I don't recall seeing significantly more than 1000 W/m2. The nominal average 1.362 kW/sq meter at solar max is at the top of the atmosphere, and is normal to the incidence. The surface insolation at the equator when the sun is directly overhead is about 1.04 kW/sq meter. I think you'd get pretty close to that at solar noon in the Summer in Southern California, which is 32-34 degrees latitude, so at the solstice, the zenith angle is 10 degrees, and cos(10) is pretty close to 1. You do pick up some additional insolation from diffuse and scattered radiation from clouds or haze, but I'm not sure that makes up for the attenuation due to the same haze. Some time ago, I calculated that in Los Angeles (34 degrees latitude), a horizontal flat plate gets about 8-9 kWh/m2/day in summer and about 1-2 kWh/m2/day in winter.. Tilting the collector would help a lot in the winter (Zenith angle is 56 degrees instead of 10), but there's no making up for the short days. Getting back to the time-nuts aspects, there are some charts around that show the temperature variation as a function of depth, latitude, soil and season. I know that for DSN, they went through all kinds of gyrations to calculate (and measure) this for the optical fiber timing links between the antennas and the masers. For small dissipated power (I doubt your oscillator is going to be putting kilowatts into the soil) you don't have to go very deep (single digit meters) before the diurnal variation is down in the 0.1 degree or smaller. Annual variations are bigger. http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm has a bunch of charts for some unknown latitude (probably mid Atlantic states, since the data is from Virginia Tech). They appear to use well water temperatures as the measurement technique. A bit more googling found a paper by one G. Florides that refers to the Kasuda formula.. (the link is hard to cut and paste.. I'm sure if you google Florides soil temperature you'll find it) and gives this reference Kasuda, T., and Archenbach, P.R. Earth Temperature and Thermal Diffusivity at Selected Stations in the United States, ASHRAE Transactions, Vol. 71, Part 1, 1965. Horizontal ground heat means that you are harvesting sunshine accumulated in the top one meter of the soil. Much of the energy is harvested from freezing the water around the pipe thus pulling out the relatively high melting energy of water. ___ 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] ocxo
Hi The ADEV of the reference source (OCXO / external reference) will most certainly impact the performance of the counter. The device is just comparing the input signal to the reference. Which ever one has the worse stability will limit the measurement. At some point (inside the 90 MHz VCXO’s PLL) jitter on the reference is no different than jitter on the signal you are trying to measure. If they do as many do, there’s a PLL that locks the OCXO up to the external reference through a narrowband loop. You then have two filter corners to worry about. One between the 90 MHz and the OCXO, the other between the external ref and the OCXO. Bob On Nov 23, 2014, at 8:48 PM, Don Latham d...@montana.com wrote: From the manual, I infer the dac is 10 bit. ( 4096 max count) Span is 5 volts. I've connected the gpsdo and the clock error light does not light; I'm assuming the morion is locking to the gpsdo OK. I do have the original, was going to open it up sometime. I suspect something wrong with the heater. Should just start by measuring current into + and - 15 volts. I think that Said's device could just be put inside the SR fb, and convert the external input bnc to the gps antenna. No sweat. Even the low end clock osc would work quite well, no fancy ocxo needed. SR can also be used with internal clock if needed. The dac value is saved so the internal osc is automatically calibrated by this technique. I'm really impressed by this box! A lot of thought went into it. Don Bob Camp Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle
Re: [time-nuts] ocxo
Hi The main question is - is there a PLL between the external ref and the OCXO? If so does it go through the DAC? If there’s a PLL through the DAC, then bits do matter. If the DAC is simply a replacement for a trim pot, then it may not matter much at all. The OCXO will likely age more in a few days than the reported LSB resolution of the DAC. I’d bet DAC is not part of a PLL. Bob On Nov 23, 2014, at 8:04 PM, Neil Schroeder gign...@gmail.com wrote: No but a little math based on your ocxo's range can help... but measuring it in person does give you the best numbers. More precision and more bits WON'T hurt here and the application notes from the leading crystal makers suggest a DAC front ended by a precision op amp with and that the xo be followed by a buffer. So I took the nuclear option: http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf My Wenzels don't have a reference out and neither do any of my VCXOs, but my $30 Vectron from Ebay does - so my circuit for it is modified to accept its reference voltage (its also plugged into an ADF4001 now) NS On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp kb...@n1k.org wrote: Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector so an external 5/10 MHz source can lock the internal oscillator. The external 5/10 MHz source proceeds to the phase detector thru an identical buffer chain without the switched divider. The remainder of the clock circuits is a multiplier to 90 MHz. I'll run the autocal tomorrow and then get some jitter stats if possible. This is an early specimen, s/n about 700 or so. I can imagine seldom used, and sitting on standby for 20 years or so, pushing the ocxo out of tolerance. The saga continues; I may have to look for a 10 MHz replacement on epay, there isn't room to put in an Hp, unfortunately. Don Bob Camp Hi At least the Morion’s I have seen have 5 MHz crystals in them rather than 10 MHz. They have a 10 MHz output due to an internal doubler. Since the circuit is not perfect, there is cycle to cycle variation in the 10 MHz. It’s way more jitter (measured in picoseconds) than the oscillator has due to phase noise. My concern is that a counter might be bothered by this is some subtle way. Bob On Nov 22, 2014, at 3:55 PM, Don Latham d...@montana.com wrote: Hi Bob: no. cobble, not double :-) A little
Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps
Thanks to all for the response but the distribution amp additive noise can be a real problem since the 10 MHz to be distributed is -170 dBC/Hz at 10 KHz and needs to be preserved if at all possible. BTW, the Ettus Octobox doesn't have a spec for additive phase noise, so that's out. Again thanks...Bill -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Sunday, November 23, 2014 1:09 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps Hi For any “real world” source being distributed, simple high speed CMOS buffers will not add enough noise to matter at 10 MHz. That of course also assumes that the target gear is the normal bunch of instruments that we all play with. Bob On Nov 23, 2014, at 11:47 AM, Bill b...@hsmicrowave.com wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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] rs-422 rs-232 to fast ethernet converter
If you feel like building : http://www.ti.com/tool/tida-00226 You can integrate that further than a cots one On Sunday, November 23, 2014, Joseph Gray jg...@zianet.com wrote: Didier has a good suggestion as to the serial to Wifi adapter. I may order one for my Z3801. Looking on Amazon, I see these two units that are more reasonably priced: http://www.amazon.com/Keynice-Ethernet-Intelligent-Communication-Wireless/dp/B00JTUVA0G/ref=pd_sim_sbs_e_1?ie=UTF8 http://www.amazon.com/Ethernet-Serial-RS232-RS485-Converter/dp/B00ATV2DX2/ref=pd_cp_pc_1 Joe Gray W5JG On Sun, Nov 23, 2014 at 11:59 AM, Graham planoph...@aei.ca javascript:; wrote: Thanks Didier, Good suggestions and I have been considering something similar. cheers, Graham ve3gtc On 2014-11-23 13:26, Didier Juges wrote: Graham, There are a number of WiFi to serial modules like the one I use on my Thunderbolt monitor: The Microchip WiFly RN-XV-171. Once configured (typically using a PC), they will present a TCPIP port (TCP or UDP) from which you can get and send data directly to the serial port. Alternately, you can use Digi XBee modules that work like wireless RS232 isolators. I use the XSC Pro 900 MHz for a number of projects, including data loggers that are out of WiFi range. You can get well over a mile in open space with those. They are limited to 19200 bauds at the most. Didier KO4BB On November 22, 2014 4:47:15 PM CST, Graham planoph...@aei.ca javascript:; wrote: I have been contemplating how I will would like to interface to the KS-23461 devices using rs-422. One option is a rs-422 to USB cable. Seems easy enough. But another option I keep stumbling across is a rs-422/rs-232 to fast ethernet such as: http://www.transition.com/TransitionNetworks/Products2/Family.aspx?Name=SDSFE3110-120 Frankly, I have no first hand knowledge or experience with these devices. First glance suggests that it might just be what I want - easy access to the KS-23461 ports through a connection to my local network without having a PC of some sort close by. So, any first hand experience with such devices? Good idea or bad? cheers, Graham ve3gtc ___ time-nuts mailing list -- time-nuts@febo.com javascript:; 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 javascript:; 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 javascript:; 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 Additive Phase Noise 10 MHz Amps
Hi While OCXO’s that have -170 dbc/ Hz specs are fairly common, they normally go deep inside a box of some sort. It’s a rare off the shelf device that takes in the output of a distribution amp *and* requires that sort of phase noise. What’s your target device(s)? Why do I ask? Well, a device that has a -170 dbc floor combined with a -170 dbc oscillator will give you -167. A device with a -200 dbc floor will still “degrade” a -170 dbc oscillator. That’s a fairly big change in circuit complexity (and cost) for a 2.9 something db improvement. The list of devices that might make it worth spending (say) a few hundred dollars a channel versus under a buck a channel is pretty short. That may put a bound on this. One example may help: If you are running phase noise testing, forget about multi channel distribution amps. They will add a ground loop(s) / pickup loop(s) that you will be fighting forever and ever. Do that sort of stuff straight off the oscillator. There is no rational amount of money (ummm …. e … how much do you have?) you can spend to get around this. A second (or eighth) oscillator is cheaper than even some of the simple approaches that don’t work very well. The type of OCXO you are talking about is a $50 item on eBay. Bob On Nov 23, 2014, at 9:17 PM, Bill b...@hsmicrowave.com wrote: Thanks to all for the response but the distribution amp additive noise can be a real problem since the 10 MHz to be distributed is -170 dBC/Hz at 10 KHz and needs to be preserved if at all possible. BTW, the Ettus Octobox doesn't have a spec for additive phase noise, so that's out. Again thanks...Bill -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Sunday, November 23, 2014 1:09 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps Hi For any “real world” source being distributed, simple high speed CMOS buffers will not add enough noise to matter at 10 MHz. That of course also assumes that the target gear is the normal bunch of instruments that we all play with. Bob On Nov 23, 2014, at 11:47 AM, Bill b...@hsmicrowave.com wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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. ___ 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] Practical considerations making a lab standard with an LTE lite
On 11/23/14, 5:46 PM, Brooke Clarke wrote: Hi Jim: It turns out that ground water that's being pumped is very similar to pumping oil. It's a limited resource. There's a web page showing the GRACE satellite maps of California and that we are running out of ground water. Back east where that data is from, I suspect that's not a big an issue. Water is many tens of meters down in most of 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] Practical considerations making a lab standard with an LTE lite
Charles, Any buffer options added to the board would have caused either additive phase noise or added power consumption, and possibly yet another low noise LDO to be required. On the 20MHz units there is already a strong buffer that can drive 50 Ohms terminations so adding a buffer in front of the coax connector on that version would have just added unnecessary phase and AM noise, parts count and cost, and power consumption, and would have resulted in a product with worse performance than we have now. That configuration is the normal one so we did not add unnecessary circuitry that would have decreased product performance. On the 10MHz boards with external DIP-14 TCXO there is no buffer, and adding one would have required to possibly add yet another low noise supply regulator and possibly another MMCX connector. Since this is the optional configuration, we optimized for highest performance for the standard configuration. Adding this many features to the board required some trade offs to be made, and we have to keep in mind the initial goal of the entire effort: to provide an easy way to evaluate the performance of our LTE Lite module - hence its called the LTE Lite Evaluation board. Everything else was a bonus. But in the end it should be fairly trivial to put a 50 Ohms driver and low pass filter together using either a CMOS gate or a simple emitter follower. We also need to keep in mind that generating a Sine Wave output would have consumed 200mW to 250mW additive power and thus would have more than doubled the total power consumption. Lastly we have three outputs on the board so we would have required three additional buffers and their support circuitry, all that for a questionable improvement. Or instead of adding a bunch of buffers one can use somewhat short cables and 1M input impedance on the target hardware and that will work perfectly too without any changes.. Bye, Said Sent From iPhone On Nov 23, 2014, at 16:22, Charles Steinmetz csteinm...@yandex.com wrote: Said wrote: The 10MHz units have a different RF output than the 20MHz units. The 20MHz units have a 50 Ohms series-terminated and buffered RF output, while the 10MHz units have the TCXO output drive the MMCX connector directly without series impedance matching. Both drive the line with 3.0V CMOS levels. This means the cable on the 10MHz unit should be kept as short as possible, and that impedance matching for maximum power-transfer is not required nor desired. The suggestion that Charles made for checking the impedance by progressively loading the output more and more is valid for Sine Wave outputs, but not for CMOS outputs as implemented on the LTE Lite. Absolutely correct -- I did not anticipate that anyone would make unbuffered logic levels available to the external world. In that case, I'd put a logic-level line driver immediately at the unit (by immediately, I mean with a small breakout card that plugs directly onto the LTE's MMCX connector with no intervening cable). For example, all 6 outputs of an HC14 or AC14 hex inverter connected in parallel, or a dedicated line driver chip like an HC365/366 or AC240/244/540/541. The buffer should be inside the enclosure with the LTE, and I would also add a T-network filter to convert the logic-level square wave into a sine wave. This would confine all of the fast logic transitions inside the shielded box, where they can do the least mischief. For the T-network, I like 10uH/50.5pF/10uH, others like 1.5uH/310pF/1.5uH. Both draw ~ +/- 35mA from a 5v logic output. Make sure your buffer can supply this current, and feed the T-network through 10nF and 50 ohms in series. You'll get a 1Vrms (13dBm) sine wave into 50 ohms (675mVrms with 3v logic). H3 is down 40dBc with the 1.5uH network and 60dBc with the 10uH network. [Note that the apparent source impedance is 50 ohms, so the open-circuit voltage is more than double.] Best regards, Charles ___ 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] Practical considerations making a lab standard with an LTE lite
In message 54723237.7070...@pcscons.com, Alex Pummer writes: by us in central California, we get 1kW/h square meter average around the year, the south even more, el Cajon will have today +29C° in the afternoon as of 23 of November 2014 Yes, the latitude means a lot for ground heating, both in terms of Sun radiation angle and length of winter. -- 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.
Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps
Hi Bob, Thanks for your comments. The devices in my lab that can benefit from the low phase 10 MHz source are 1) the spectrum analyzer(s), 2) a Comstron direct synthesizer, 3) the synthesized signal generators and the test source(s) used to drive microwave multipliers and signal sources. All these devices will see the 10 MHz phase noise (improvements) within the narrowest PLL the devices use. After spending bucks for a low noise 10 MHz source, I can't afford to use one for each instrument. Besides it would hurt to go through the trouble of buying a low phase noise 10 MHz reference and lose it in a poor distribution amplifier(s). Also, the advantages of running all instruments from the same 10 MHz source are well known. So while I was hoping to short circuit some of the design/prototyping effort in the hopes someone on this thread had been there, I'll just hit the books and do some prototyping and noise testing and see what I come up with. Regards...Bill -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Sunday, November 23, 2014 7:08 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps Hi While OCXO’s that have -170 dbc/ Hz specs are fairly common, they normally go deep inside a box of some sort. It’s a rare off the shelf device that takes in the output of a distribution amp *and* requires that sort of phase noise. What’s your target device(s)? Why do I ask? Well, a device that has a -170 dbc floor combined with a -170 dbc oscillator will give you -167. A device with a -200 dbc floor will still “degrade” a -170 dbc oscillator. That’s a fairly big change in circuit complexity (and cost) for a 2.9 something db improvement. The list of devices that might make it worth spending (say) a few hundred dollars a channel versus under a buck a channel is pretty short. That may put a bound on this. One example may help: If you are running phase noise testing, forget about multi channel distribution amps. They will add a ground loop(s) / pickup loop(s) that you will be fighting forever and ever. Do that sort of stuff straight off the oscillator. There is no rational amount of money (ummm …. e … how much do you have?) you can spend to get around this. A second (or eighth) oscillator is cheaper than even some of the simple approaches that don’t work very well. The type of OCXO you are talking about is a $50 item on eBay. Bob On Nov 23, 2014, at 9:17 PM, Bill b...@hsmicrowave.com wrote: Thanks to all for the response but the distribution amp additive noise can be a real problem since the 10 MHz to be distributed is -170 dBC/Hz at 10 KHz and needs to be preserved if at all possible. BTW, the Ettus Octobox doesn't have a spec for additive phase noise, so that's out. Again thanks...Bill -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Sunday, November 23, 2014 1:09 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps Hi For any “real world” source being distributed, simple high speed CMOS buffers will not add enough noise to matter at 10 MHz. That of course also assumes that the target gear is the normal bunch of instruments that we all play with. Bob On Nov 23, 2014, at 11:47 AM, Bill b...@hsmicrowave.com wrote: What's the latest opinion (data) on available low additive phase noise 10 MHz amplifiers for 10 MHz distribution? Regards and thanks.Bill ___ 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. ___ 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 Additive Phase Noise 10 MHz Amps
I did some checking around for low noise buffer amps earlier this year. They needed to have 200 MHz bandwidth, so this isn't directly applicable to 10 MHz. I also needed isolation. About the only information in print is from the usual suspects at NIST. They wrote a series of papers taking a fairly classic discrete design and refining it. Check FCS proceedings. My idea was to take ideas from 10 MHz and extend them to 200 MHz. I didn't see any really profound ideas in the NIST papers. There is a reproducibility problem because the original discrete devices may not be available, or NIST might have used special hand picked devices. BTW, I cringe when I see the term additive phase noise. Phase noise, as all time nuts know, is NOT ADDITIVE NOISE, as in AWGN. It is multiplicative. The correct term, IMHO, is residual phase noise. What additive noise refers to is the classic noise figure type noise involving small signals. Again, as all time nuts know, low NF is necessary but not sufficient for low phase noise. Rick Karlquist N6RK ___ 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] ocxo
The 90 MHz is multiplied up from the 10 MHz, no pll. Done with a 10 mhz rate 5 ns pulse and a filter chain, followed by a comparator and buffer. from the manual: The SR620 has a rear panel input that will accept either a 5 or 10Mhz external timebase. The SR620 phaselocks its internal timebase to this reference. The phase-locked loop has a bandwidth of about 20Hz and thus the characteristics the the SR620's clock, for measurement times longer than 50ms, become that of the external source. For shorter measurement times the clock characteristics are unimportant compared to the internal jitter (25ps rms) of the SR620. Thus, if the signal from a Cesium clock is input into a SR620 with a standard TCXO oscillator the short-term and long-term stability of the SR620 will become that of the Cesium clock. Yes, all jitter is relative... Don Bob Camp Hi The ADEV of the reference source (OCXO / external reference) will most certainly impact the performance of the counter. The device is just comparing the input signal to the reference. Which ever one has the worse stability will limit the measurement. At some point (inside the 90 MHz VCXO’s PLL) jitter on the reference is no different than jitter on the signal you are trying to measure. If they do as many do, there’s a PLL that locks the OCXO up to the external reference through a narrowband loop. You then have two filter corners to worry about. One between the 90 MHz and the OCXO, the other between the external ref and the OCXO. Bob On Nov 23, 2014, at 8:48 PM, Don Latham d...@montana.com wrote: From the manual, I infer the dac is 10 bit. ( 4096 max count) Span is 5 volts. I've connected the gpsdo and the clock error light does not light; I'm assuming the morion is locking to the gpsdo OK. I do have the original, was going to open it up sometime. I suspect something wrong with the heater. Should just start by measuring current into + and - 15 volts. I think that Said's device could just be put inside the SR fb, and convert the external input bnc to the gps antenna. No sweat. Even the low end clock osc would work quite well, no fancy ocxo needed. SR can also be used with internal clock if needed. The dac value is saved so the internal osc is automatically calibrated by this technique. I'm really impressed by this box! A lot of thought went into it. Don Bob Camp Hi About the only other question would be the proper resolution for the DAC. There’s not much of a way to to answer that one without playing with a woking original OCXO. Bob On Nov 23, 2014, at 7:22 PM, Don Latham d...@montana.com wrote: No question about that. The morion does run a little warmer than the old unit apparently did. Fan is temp-controlled, so I think OK. will monitor box temp with a digital :-) thermometer, very poor resolution, but probably ok. When I get the last obs done. will do a little blurb to the group. Don Bob Camp Hi That sounds fine. Without knowing just what they did or didn’t do, it’s always worth being a bit careful. Bob On Nov 23, 2014, at 6:40 PM, Don Latham d...@montana.com wrote: Running very nearly continuously for about 4 days now. The self-measured jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with the Morion. I'm using my newly acquired cs source and a couple of z3801's for checking. 1 bit on the SR's frequency calibration dac seems to be about 4-5 parts in 10^-10 if I'm reading things right. Next test is a z3801 driving the external freq port on the sr to see if the frequency change direction of the morion is OK. The scope display output from the SR620 is great! Lots to learn. Also have one of Said's units coming. Gone nuts for time, won't do anything much new, but it's new to me. All this to drive moonbounce... Don Bob Camp Hi If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be important at all. It’s just something to watch for. If you start seeing data in two groups, each one 20 ps wide and separated by maybe 200 ps, you are seeing a problem from the 5 MHz. Running the box for a while before doing a full detailed cal is a very good idea. It’s a bit warm inside and some of the stuff is temperature sensitive. You want it to reach equilibrium. Bob On Nov 23, 2014, at 1:06 AM, Don Latham d...@montana.com wrote: Ah. Got it finally! Doh. Just finished trying out the Morion this afternoon. Electrically works very well. Used a 7812 to drop the +15 volts from the option 1 ocxo, there is enough power headroom to bring the Morion up from cold and run it comfortably. As you said, the control voltage for the original is indeed 5 v, and can be set by the internal d/a. The output of the oscillator passes through an emitter follower voltage adjuster and through a low-q filter to three stages of ECL buffer and then out to the 10 MHz system bus clock. Another path proceeds to a relay-switched divide by 2 to the phase detector
