Re: [time-nuts] Need help phase locking with small offset
stewart.c...@gmail.com said: > The question is how to lock the 100 MHz OCXO to the 10 MHz reference input > with a slight offset, so that the OCXO frequency is "exactly" 100,000,100.000 > Hz (for example). Do you need to lock it? If the 10 MHz reference is one of your inputs, can you work out what the actual frequency of your 100 MHz OCXO is and use that to figure out the frequency of the other inputs? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Thunderbolt E failing
p...@phk.freebsd.dk said: > I later talked to a geologist who knows the Danish underground well, and he > estimated I would have needed to drill to at least 25m depth to escape > seasonal temperature-changes and cited a research paper from the 1950'ies > where the did precisely that experiment. I found a paper showing skin depth at 1 year of 3-4 meters for soil, a bit over 1 meter for ice and rock. Does a pipe in the ground stay dry? Or how do you keep in dry? In summer, I'd expect it to be cool and if the humidity in the outside air is above X% it would condense in the pipe. Do you just cover the top to avoid air mixing? Does in need a desiccant? ... -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] 74AC175 Chips for PICTIC II
Greetings, Several years ago, Bob Bownes provided a generous response to my request for PICTIC II support. In return, he asked only that I "pay it forward." I recently located two apparently new Harris CD74AC175E chips in the DIP package that became obsolete during that era, rendering otherwise complete PICTIC II boards useless. In the spirit of Bob's generosity, I will gift one chip to each of the first two responders who have PICTIC II boards ready to accept the chip. Regards, Peter ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] distribution amps for 200 MHz
Some CATV distribution amplifiers have built-in 4 or 8 way splitters and work over 60-900 MHz. They are cheap enough that's it's worth trying. Didier KO4BB On Tue, Sep 15, 2020, 4:57 PM Poul-Henning Kamp wrote: > > jimlux writes: > > > For work, I'm looking to distribute 200 MHz to 44 widgets.. > > The usual SRS, etc. boxes max out at 100 MHz. Any ideas? > > A lot of video-production amps would have no trouble with that > but they're all 75 Ohm... > > -- > 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@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] distribution amps for 200 MHz
jimlux writes: > For work, I'm looking to distribute 200 MHz to 44 widgets.. > The usual SRS, etc. boxes max out at 100 MHz. Any ideas? A lot of video-production amps would have no trouble with that but they're all 75 Ohm... -- 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@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Thunderbolt E failing
shouldbe q931 writes: > > Apart from the entire "get electronics wet" thing, water would have > > been near perfect. > > There are alternatives to water... > https://www.3m.co.uk/3M/en_GB/novec-uk/applications/immersion-cooling/ For very, very specific use-cases, yes. I have hard time seeing anybody dunk their OCXO or Rb... -- 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@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] distribution amps for 200 MHz
I also need ~200 MHz buffers for a client. See: State-of-the-Art RF Signal Generation From Optical Frequency Division Sept 2013 IEEE Trans UFFC, p 1796 In Table I (top of page 1798) they list the RFMD RF2312 amplifier. Table II top of page 1799 shows that this is good for -150 dBc/Hz at 1 Hz for a 5 MHz carrier. The bandwidth of this amplifier goes way beyond 200 MHz, so I am assuming the phase noise should be good at 200 MHz. Maybe not 150 dBc/Hz, but still respectable for 200 MHz, vs other amps. RFMD went through a half dozen mergers and the RF2313 is now made by Qorvo and sold thru the usual distributors. I characterized it and it wants to be used in a 75 ohm, not 50 ohm system. There are always transfomers... My HP11848 went south so I was never able to measure its phase noise at 200 MHz. Anyone have have an 11848 to sell? If someone would like to measure it for me, I will be happy to send an evaluation board. Rick N6RK On 9/15/2020 11:17 AM, jimlux wrote: For work, I'm looking to distribute 200 MHz to 44 widgets.. The usual SRS, etc. boxes max out at 100 MHz. Any ideas? (The going in position is "buy a bunch of minicircuits amps and dividers and assemble it") Tnx Jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] distribution amps for 200 MHz
Cheap Chinese rf amps ebay, also TV splitters On 2020-09-15 12:17, jimlux wrote: For work, I'm looking to distribute 200 MHz to 44 widgets.. The usual SRS, etc. boxes max out at 100 MHz. Any ideas (The going in position is "buy a bunch of minicircuits amps and dividers and assemble it") Tnx Jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. -- Dr. Don Latham AJ7LL PO Box 404, Frenchtown, MT, 59834 VOX: 406-626-4304 ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] distribution amps for 200 MHz
Jim You beat me to the exact answer I would have given you. Its a bit trickier than that in the splitter setup. But I know from previous posts you know that already. Thinking noise from the amps may be the trickiest part. Regards Paul WB8TSL On Tue, Sep 15, 2020 at 3:23 PM jimlux wrote: > For work, I'm looking to distribute 200 MHz to 44 widgets.. > The usual SRS, etc. boxes max out at 100 MHz. Any ideas? > > (The going in position is "buy a bunch of minicircuits amps and dividers > and assemble it") > > Tnx > Jim > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Need help phase locking with small offset
I totally agree with the others warning to avoid processing too many different signals within a FPGA or any kind of part with multiple functions. There will always be some amount of crosstalk, so any device should be used only for one frequency chain, and only that frequency's related harmonics and subharmonics will be in there. It's tempting to get as much function as possible in the minimum parts count, but it's cleaner to keep things separated - part-wise, and also physically and power-wise too, and sometimes separately contained and shielded if needed. Regarding PLL methods, I'd suggest looking at under-sampling the 100.0001 MHz with the 10 MHz reference, say, with a DFF, to get the direct difference between 10x10 MHz and the 100 MHz + 100 Hz. This would skip most of the dividing and give 100 Hz comparison frequency, which is nicer than 10 Hz. The 100 Hz reference can easily be made with decade dividing from the 10 MHz. So, instead of lots of dividers, your FPGA or whatever DFFs could be used for sampling and metastability correction. In this case, one part would hold the sampler processing to make 100 Hz from the two inputs. The reference divider should probably be within a separate part, according to the concepts of the first paragraph above, keeping its intermediate divider frequencies away from the front-end process. Later, you can try to do it all in one part and see how it works out. This all is of course not as frequency-agile as other methods that can be done with programmable dividing, but for one or a few fixed offsets, may be the simplest approach. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] distribution amps for 200 MHz
For work, I'm looking to distribute 200 MHz to 44 widgets.. The usual SRS, etc. boxes max out at 100 MHz. Any ideas? (The going in position is "buy a bunch of minicircuits amps and dividers and assemble it") Tnx Jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Thunderbolt E failing
On Mon, Sep 14, 2020 at 10:36 AM Poul-Henning Kamp wrote: > > > Matthias Welwarsky writes: > > > > The point is that there is no need to compensate the part while it is > > > locked. > > > > It depends. For short time constants, yes, likely the control loop is able > > to > > follow the temperature-induced drift of the OCXO. But you might want the TC > > to > > be as long as possible. > > The word you are looking for here is not "Temperature Coefficient" > but "Thermal Impedance" (more on this below). > > > By following the temperature, you have an additional input that allows > > the controller to act more quickly to a changing environment. Effectively > > this > > will lead to higher stability of the output. > > Only if you first spend months and years measuring all the parameters > and time constants of the multiphysics model you use, well enough > to make useful predictions with it. > > > Maybe, but a linear approximation is probably better than nothing [...] > > No, it is usually worse. > > A major part of the trouble is the complex hysteresis-effects when > the temperture changes direction: The components which warm fast > also cools fast. > > For example: When the temp goes up you will likely find that your > DAC warms faster than the XTAL, but when the temp goes down it also > cools faster than the XTAL. > > That means the temperature difference between the DAC and XTAL depends > on the temperature rising or dropping, so you have to model the tempco > and temperature of them individually. > > > If you look at the attached screenshot - there's roughly 5500 seconds of > > data > > from my GPSDO. At about 2500 seconds the temperature compensation was > > engaged. > > This is nowhere near enough data to show anything. Collect a full > week with/without and we can talk. > > In the end, the proof is in your allan-variance, if it improves, you got > something, if it does not, you wasted your time. > > > The easiest and cheapest way for you to get better results, is to increase > the thermal impedance between the surroundings and your GPSDO. > > That will make the temperature change slower, which also means it > changes less and therefore your hysteresis effects also get smaller. > > Note that "thermal impedance" is not the same as "thermal insulation": > > Thermal insulation materials have high thermal resistance and low > thermal mass, and wrapping your GPSDO in that would just make it > run hot. > > Think of it is a thermal RC filter with a huge resistor and a small > capacitor. > > We want the a low to moderate resistor, so the GPSDO can still dump > its heat, with a huge capacitor to filter out the changes in > temperature. > > Apart from the entire "get electronics wet" thing, water would have > been near perfect. There are alternatives to water... https://www.3m.co.uk/3M/en_GB/novec-uk/applications/immersion-cooling/ Cheers Arne > > Table-top granite (about 2cm thick) is really great, but not very accessible. > > Metals almost conduct heat too well, but a box of 1-5cm thick iron > plates works great, but pay attention to the weight. > > For most of us, concrete is the way to go: > > Get three cinderblocks of the kind that looks like a 'H' with two > horizontal bars. > > Put the first cinderblock down on its side. > > Put the next cinderblock on top of it in normal orientation. > > Put your OCXO into the cavity. > > Hack notches in the edge of the cinderblock for the cables. > > Put the third cinderblock on top, also on its side. > > You have now increased the thermal impedance by almost two orders > of magnitude, and your PLL will be boored. > > If need be, you can make the central cavity more air-tight by > "sealing" between the cinderblocks with a layer of cloth or > tissue-paper. > > -- > 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@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Thunderbolt E failing
ew via time-nuts writes: > In 1973 I moved for TI to Dallas and had a 20 foot hole drilled to place my > Sulzer One alternate.. Today I monitor my lab closely to better understand > what to do. The monitor is placed on the top of the HP5065A[...] When we built our new house I wanted to build some kind of "clock vault", but however I looked at it, it was either far too expensive or impossible to get planning permission for due to the ground water protection zoning. I later talked to a geologist who knows the Danish underground well, and he estimated I would have needed to drill to at least 25m depth to escape seasonal temperature-changes and cited a research paper from the 1950'ies where the did precisely that experiment. He also mentioned something I had not thought about my self: The ø=15cm end-capped dry steel-pipe I was dreaming of would have been subject to a LOT of upward boyancy force. -- 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@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
