[time-nuts] Samsung GPSDO : Chinese surplus
All the UCCM receivers have a EXT option... but most refer to it as LINK. Heather sets it to GPS on startup. I believe LINK/EXT selects an external PPS/PP2S provided by the base station. I think they normally operate it in GPS mode and switch to EXT if the GPS goes down. -- > I'm still intrigued though by the very existence of that EXT/GPS software > switch as a configuration option for the GPSDO itself, and wondering just > what EXT might actually imply in this instance. ___ 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] time-nuts humor
On Wed, Sep 19, 2018 at 1:48 AM Eric Scace wrote: > > For a good time, call 303-499-7111 > > (Sorry! My girlfriend made me do this.) In the UK, the number used to be 123, which was quite pleasing when I discovered ntp. ___ 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] Noise of digital frequency circuits
Attila Kinali writes: > Yes. This effect has been known for a few decades at least. What kind > of puzzles me is, that I have not seen a mathematically sound > explanation of it, so far. I'm afraid I can't help with the rigor, but the fundamentals seem simple enough to me. > People talk of aliasing and sampling, but do not describe where the > sampling happens in the first place. After all, it's a > time-continuous system and as such, there is no sampling. That may be quibbling over terminology and definitions not actually specified in those papers. Localization in the frequency domain requires periodicity in the time domain (by definition) and moving spectral features around can be done by convolution of the noise spectrum with a localized signal (not necessarily of compact support, but assume for the moment it is so you get a clearly defined pivot frequency). That means you need to do multiplication in the time domain with something periodic, so all you need to produce noise folding is for instance a periodically varying NTF. I guess we can tick that box in all instances you've mentioned. > One could look at it as a (sub-harmonic) mixing system, but > even that analogy falls short, as there is no second input. Does it even matter if you call it a "second input"? Reading the Egan paper I guess the line of arguments that leads to "sampling", "mixing" and "aliasing" getting used is that the periodically varying NTF (or ISF if you like) looks and acts sufficiently like a Dirac comb that you can use sampling theory to interpret the results. Or conversely, that you can take the results and postulate a sampling process with a sampling aperture that happens to look virtually identical to (one period of) your NTF. This seems not much different than what gets routinely done when reasoning about real-world systems that do "proper" sampling, but of course do not sport a perfect dirac pulse sampling aperture. > It also fails at describing why there is not infinite energy being > down-mixed, as the resulting harmonic sum does not converge. The actual integral or sum to compute would likely be governed by something sinc-like, so convergence would eventually still happen with any physically realizable input. That assumes you don't already need to start with some generalization of the Fourier transform that has more strictly defined convergence behaviour. […] >> > If you divide by something that is not a power of 2, then it is important >> > that each stage produces an output waveform with a 50% duty cycle. >> > Otherwise >> > flicker noise which has been up-mixed by a previous stage, will be >> > down-mixed >> > into the signal band, increasing the close-in phase-noise. >> >> Wow, another thing I never knew. > > I do not think that anyone was aware of this. Funnily a paper I just read in TCAS-I (February 2017) by Pepe and Andreani about phase noise in harmonic oscillators seems to mention this (I think) as a known result w.r.t. flicker noise upconversion and generalize (ref. eq. 90) on previous results for several particular oscillator topologies which guarantee the necessary conditions. There is also lots of discussion about the relation to the ISF and results in conjunction with it that goes right above my head. The direction their math is taking looks intriguing, so maybe you are able to glean something from it to use. Whether there's any pre-existing link of those results specifically to frequency dividers I don't know. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ SD adaptations for KORG EX-800 and Poly-800MkII V0.9: http://Synth.Stromeko.net/Downloads.html#KorgSDada ___ 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] Efratom Oscillators
Anyone, I have two Efratom EMXO Series Sub-miniature Quartz Oscillators I'd like to test before parting with them. Does anyone have a datasheet or pinout and supply voltages? They supposedly have pins for oven power, oscillator power and TTL power! Thanks, Bob Martin ___ 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] Samsung GPSDO : Chinese surplus
I had to make several changes to Lady Heather to work with these... you may have an earlier version. How are you connecting the serial port? In the photo, I did not see the row of four holes that is on the Trimble / Symmetricom versions. --- Hi Mark The serial port connections are on the 50 pin flatstrip header, as per diagram here.. http://tipok.org.ua/node/53 That's based on the Trible/Symmetricom versions and is shown with the connector removed but so far what I've checked matches up. Fortunately my unit was supplied with a breakout board to convert the flatstrip to a double row of 0.1" spaced holes, and a couple of rows of header strip plus an old flat SCSI cable fitted a treat:-) I realised there must be variations with this one over and above what you'd sorted earlier but thought it worth a mention in case it gave you any pointers, the real issue though is still that as it stands it can never boot into GPS mode without outside intervention anyway. I did wonder if it could have received the appropriate configuration commands for whatever unit it was sat in but that should have been obvious to anyone who powered one up, which it might have been of course:-) For now I've switched to the view that this one may have either a hardware or software fault that's preventing it booting up properly and am currently awaiting further response from the seller. As it stands it's certainly not a very practical option if it needs a permanently attached PC to manage the boot up, although once booted it is looking quite good, as is the little Ublox LEA-6T. I'm still intrigued though by the very existence of that EXT/GPS software switch as a configuration option for the GPSDO itself, and wondering just what EXT might actually imply in this instance. Nigel GM8PZR ___ 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] Samsung GPSDO : Chinese surplus
I had to make several changes to Lady Heather to work with these... you may have an earlier version. How are you connecting the serial port? In the photo, I did not see the row of four holes that is on the Trimble / Symmetricom versions. ___ 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] Samsung GPSDO : Chinese surplus
These are Samsung's version of the "UCCM" series of GPSDOs. Lady Heather now works with them. I had to tweak the code to handle their funky/erratic end-of-line sequences... various versions of CR/LF, LF, LF/CR. Their STATUS screen and some message responses are also a bit different. They do tell you the antenna current... - I'm not sure, but to borrow from Orwell, I do suspect that some Samsung UCCM modules may be more equal than others, so here's a warning to the curious, sorry, M R James that time:-) Anyways, after Greg posted information about these earlier this month I bought one of the STP2945LF versions from Ebay auction 332792680396 and the one that arrived a couple of days ago is the actual item currently pictured in that auction, condition is very good and a flatstrip interface connector was an unexpected bonus so certainly no problem there. Whether or not I've just missed something and ended up reinventing the wheel I don't know, but after first believing wrongly that this unit must be faulty here is what I've found so far.. The supply voltage seems to be quite critical, inasmuch as the alarm light is on if the supply is below approx 5.5 volts, it certainly doesn't like 5 volts, and it comes on again if the supply is increased to just over 6 volts. At the upper limit there's no immediate obvious other effect but at the bottom limit the unit seems to drop immediately into holdover, this from observing plots on a Pendulum counter. Even when the supply is ok the alarm light is amber rather than green but not sure what that's trying to tell me. Trying different antennas and even a resistive load at the antenna socket makes no difference. At the moment Lady Heather doesn't seem to be hapy with this one, despite forcing baud rate and receiver type she just didn't want to know at first and insisted there was no data to be seen from the COM port, and initially the unit itself didn't seem to be doing anything very useful either However, running it into Hyperterminal did show it booting up at 57600, 8-N-1 as expected, and eventually I discovered that this unit has two options for Reference type, GPS or EXT, EXT presumably "external" and I assumed referring to what was supposed to be feeding whatever this was used in, and it defaults to EXT whenever the unit is started or after a hard or soft reset. Fortunately it's possible to run a "Ref : Type GPS" command and the activity LED quickly confirmed that it's now behaving as expected. If I run a diagnostic:loop command though it's so far always returned a figure of +1.062E-7 for the OCXO but also states that EXT is "unavailable" which might even suggest that the EXT input is an expected input to the GPSDO itself. Purely speculation of course, and the 1PPS is definitely an output at the moment... Next oddment, trying yet again to let Lady H see it I left the GPSDO running and terminated the connection in hyperterminal and started Lady H again with the receiver preset as UCCM, still nothing until I brought up the command line help screen and then Lady H started taking data in behind it only to stop again when I closed the help screen. This was very erratic though, sometimes she'd stay after the help screen was closed but sometimes lock and sometimes randomly updating, either way she certainly wasn't having a good day:-) What Lady H did manage to do was to switch the output to the continuous data stream mode and the only way I've found so far of stopping this is a hardware or software reset, either of which then sets the Reference typ to EXT again:-( So that's it for now, still playing but I did think it was worth alerting other potential buyers as to what they might expect. Not all doom and gloom though, and believe it or not I'm even inclined to recommend it, Lady H has shown over a dozen sats with good signal levels at times, that's pretty remarkable for here, and it does lock quickly and conditioning looks good. It would be interesting to see if holdover improves though, and if it could be persuaded to default to GPS at start up that might perhaps be a bit more useful:-) Nigel, GM8PZR ___ 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] Noise of digital frequency circuits (was: Programmable clock for BFO use....noise)
Hi Attila, everyone, very interesting discussion! >People talk of aliasing and sampling, but do not describe where the sampling happens in the first place. After all, it's a time-continuous system and as such, there is no sampling. I would say that the sampling occurs when you're using only a slice of an input signal. For instance, If you're using only the zero-crossing slice of a sinewave to produce a divided version rather than the full envelope. It's a matter of how you process information in your circuit. >"A Physical Sine-to-Square Converter Noise Model," > by Kinali, 2018 I read the paper, very interesting as well! I have a minor remark, in the paper you relate the ISF (let's say "sampling window") to the output slew rate of the comparator. I would say that the sampling window should be related to the comparator input stage bandwidth. If you have an high bandwidth input stage (e.g. 5 GHz) followed by a slew rate limited output stage (e.g. 100 MHz) , high frequency noise will trigger the output circuit and aliasing it. Viceversa, if you have a low bandwidth input stage, even if the output stage is very fast, you don't get input noise aliasing. cheers Mattia Il giorno lun 17 set 2018 alle ore 13:46 Attila Kinali ha scritto: > On Sun, 16 Sep 2018 23:06:06 +0200 > Attila Kinali wrote: > > > [2] "A Physical Sine-to-Square Converter Noise Model," > > by Kinali, 2018 > > Oops.. I forgot to add the link to the pdf, sorry > http://people.mpi-inf.mpg.de/~adogan/pubs/IFCS2018_comparator_noise.pdf > > > Attila Kinali > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neal Stephenson > > ___ > 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] Exact Time Mobile Phone Apps
> The timing must be very low level in the OS. Yes, and it can get a bit complicated. The desktop or server case is usually straightforward. Modern CPUs have a cycle count register. You can keep time with that if you know the clock frequency. There is another register on Intel architectures that counts at a known frequency. You can use that to calibrate the main clock that drives the cycle count register. Most PCs crystals are off far enough to be annoying, so one of the main things that ntpd does is reach into the kernel via a side door to tell the kernel the correction for the clock frequency. ntpd calls that drift. It's in log files and/or stored in a file so it can be used on reboot. ntpd can be good enough that you can use the drift as a thermometer. Things get interesting when you want to change the clock frequency to save power. I think some of the early cycle-counter implementations counted actual CPU cycles. I think modern chips count at a fixed rate that may not be the same as the CPU clock frequency. If you want to save more power, you can turn off the CPU clock. Laptops do this when you close the lid. Phones do it on a much finer grain. Then you have to set the clock when you turn the CPU clock back on. I'm not sure of the details in this area. Most systems have a battery backed clock running off a 32 KHz crystal. Typically, they can only be read to a granularity of 1 second. And they aren't drift-corrected, ... -- 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.
