Re: [time-nuts] "Ancient 5065..."
Hi I think that you never really know what’s what until *you* can poke at it and try to fire it up. If the device (any device) was run for decades, parts probably were swapped to keep it running. Bob > On Oct 21, 2019, at 4:16 PM, Ulf Kylenfall via time-nuts > wrote: > > Hmm... > > On one hand the seller claims ..."is fully functional" > On the other hand the seller writes..."untested" > Strange that it has the light brown type cover plates. > My old s/n 848-00131 has the dark blue covers. > for $333 I would have baught it untested but the shippingto Sweden is another > $209. It will be interseting to seehow much money it will go for... > > > /Ulf - SM6GXV > ___ > 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] A simple sampling DMTD
Dear Attila, Thank you for your feedback, replies inline: On Tue, Oct 15, 2019 at 6:01 PM Attila Kinali wrote: [snip] > The biggest change I would make, would be to use a higher sampling > frequency and use an FPGA with a CORDIC as phase detector. Especially > as your goal is to measure the phase difference of a distribution system, > where the frequency of both inputs is exactly the same. > That's the next step (after I've taken this 8-bit processor as far as it can go). I'm working on a daughterboard with dual Lattice iCE40 UltraPlus FPGAs, picked mainly because an open toolchain is available, but also for their price and QFN48 package options (which I've not found in any other FPGA family of similar density). (note that for my purposes I do need to DMTD different frequencies, in particular the 10MHz system master clock vs the slaved 50MHz clocks on the individual SDR boards in the phased array). > The reason for this is rather simple. You are using a LMS fit over > 32 samples around the zero crossing of a 10Hz signal with a ~10MHz > sampling clock. This means you have just a few samples over what would > be otherwise possible. > It's not quite that bad, as the double CIC decimator already performs quite a bit of averaging/filtering. The LMS fit is over 32 samples out of 200 per period (after the CIC). I expect the largest improvement to come from the increase in input sample rate. > The other advantage is, that you operate close to the 1/f corner frequency, > Ie the effect of 1/f noise hits you (almost) fully. Sampling the full > sine wave instead gives you the ability to work far away from the 1/f > corner and thus greatly reduces the effect of 1/f noise. > This is definitely true, and at the moment my largest source of errors. As an intermediate step I'm considering shifting the beat frequency up some (say to 40...50Hz) and then I/Q demodulating in software.I expect this will make the filtering of LF noise easier. If you are interested, I have a parametrizable CORDIC core written > in VHDL ready for use. Thank you' I may take you up on that. So far I've been looking at the (Verilog) CORDIC code in the Ettus USRP sources. [snip] > I've been running some tests with a 10MHz sine wave from an Abracon AOCJY1 > > OCXO into a resistive divider, feeding both channels of the DMTD through > > identical SMA cables (Amphenol 135101-07-M0.50). At the ADC input this > > yields a -12dBFS sine wave (PSD of the beat note: > > > http://www.lartmaker.nl/time-nuts/PSD%20of%20AOCJY1%20into%20the%20LTC2140.pdf > > ). Over a 34000s measurement period the ZCD as described upthread (least > > squares fitting of the 32 samples nearest the zero crossing of the rising > > flank, but without DC/drift correction) shows a time difference of 6.3ps > > between the two channels, with a standard deviation of 1.6ps (full plot: > > > http://www.lartmaker.nl/time-nuts/DMTD%20Time%20between%20zero%20crossings%20with%20resistive%20divider%20(no%20offset%20correction).pdf > > ). > > I am a bit astonished by the high noise level you have. I would have > expected > this to yield something below 1ps, judging from what we got from what > Nicolas > acheived in his work on the sine exitation based TIC[1]. This is actually better than I had expected, given the drift/LF noise I get from the LTC2140 ( http://www.lartmaker.nl/time-nuts/LTC2140-14%20drift.pdf ). As I've mentioned upthread I'm looking for a robust way to cancel this drift; my best plan so far is to calculate the signal average between subsequent _falling_ edges, and to use this to get the zero level for the rising edge. (This is a problem which I would expect to have a closed form solution, even when the period of the sine is not an integer multiple of the sampling rate. Alas, my undergrad-level math seems to be failing me, so I'm resorting to the blunt instrument of numerical approximations. I hope to have more time for this in a week or two; in the meantime I'm very open for hints.) > BTW: you want to keep even harmonics as low as possible, as these lead > to increase of 1/f noise in the system (see [3] for an explanation) > Thanks, that's good to keep in mind. What I've shown is the unfiltered output of the OCXO under test; I've not attempted to do any analog filtering on this. Sincerely, JDB. ___ 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] "Ancient 5065..."
Hmm... On one hand the seller claims ..."is fully functional" On the other hand the seller writes..."untested" Strange that it has the light brown type cover plates. My old s/n 848-00131 has the dark blue covers. for $333 I would have baught it untested but the shippingto Sweden is another $209. It will be interseting to seehow much money it will go for... /Ulf - SM6GXV ___ 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] can of worms: time-of-day in a community radio station
Fiorenzo Cattaneo writes: > I have been quite puzzled about the asymmetric nature of my home Cable > Modem connection to the Internet in regard with the offset discrepancy > I observe. The "last mile" asymmetric nature of Cable Modem (Comcast > in my case) is not very high compared the delta I see between my > stratum-1 servers at home and the nearest public stratum-1 NTP server. > The upload/download discrepancy would be much less than 100 > microseconds - as you point out in your calculation the worst is 33 > microseconds for an upload speed of 12 Mbps, which is a drop in the > bucket compared to other potential sources of jitter, switch queueing > delays or asymmetric routing. The latter is not an issue in my case. The asymmetry from different bandwifth up-/downstream is only a small part of the effective up-/downstream difference. Dan Drown has measured that: https://blog.dan.drown.org/tag/asymmetric-latency/ I would think the jitter distributions are skewed as well, so some of that gets finally interpreted as an offset. If you can trust the clocks on either end of the connection to be accurate, then you can set the offset to zero and solve for the asymmetry instead of the usual assumption of zero asymmetry to solve for the offset. Plotting the offset against the RTT like Dan does is instructive, but you won't always get such nice graphs. I've attached a plot of how one of my stratum-1 has seen the three PTB servers through my DSL connection during the last three months. So while the connection is stable you can sort of remove the extra offset that comes from a changing RTT, but at any one time you might jump to one other set of correlation lines and get that "correction" wrong. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Factory and User Sound Singles for Waldorf Blofeld: http://Synth.Stromeko.net/Downloads.html#WaldorfSounds ___ 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] Ancient HP 5065A on ebay
There is an 5065A on Ebay that has the earliest SN I have ever seen. 808-00031 or maybe 00051? Maybe the first one sold? If the lamp oven has not fried it might be a fun project. It has the Patek analog clock. Cheers, Corby ___ 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] can of worms: time-of-day in a community radio station
Hi. Personally, I would not trust an "ISP" based NTP server! From personal experience, they tend to run them on the heavily congested border/gateway systems. As you can find and confirm using the usual network routing and diagnostic tools. As has been said, local GPS / Internet sync'd servers would be best, and easy to setup and maintain. The fun bit will probably be the management arguments about running one (or hopefully more) GPS receivers, and the associated cables in from the outside.. Don't forget to run them from a UPS!.. If you end up with more than one local server, and there are more than one UPS protected power sources, spread the load around and add redundancy. All that can be done on a "shoestring" and still give good quality service. Or you could raise some funds, and purchase two or three of these:- http://www.leobodnar.com/shop/index.php?main_page=product_info=120_id=272 No affiliation, but they come recommended. (And I've only just noticed that they are not far from me.) Regards. Dave B. On 21/10/2019 17:00, time-nuts-requ...@lists.febo.com wrote: > Finally, your ISP > too probably has their own NTP servers too that you may or may not > know about. -- Created on and sent from a Unix like PC running and using free and open source software: ___ 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] can of worms: time-of-day in a community radio station
I scanned the NTP pool last leap second and relayed the list of offenders to Ask. NTP pool servers may use a mixture of smeared and non-smeared upstream servers. Yuck. While the NTP pool has limitations it is widely used (and abused). NTP servers outside of the NTP pool may also be imperfect. On Mon, Oct 21, 2019 at 11:01 AM J.R. wrote: > > You can't test a server for smearieness. It wouldn't surprise me if > some of > > them turn out to be getting time from google servers or something > similar. > > True, but you *can* see which upstream time source has been selected > for a NTP server. Ask went through the pool servers last leap-second > and contacted all the owners that were returning a Google IP as their > primary time source to get them to change their configuration. > Likewise, said servers that weren't reconfigured in time were pulled > out of rotation during the event to prevent any issues. So there > *were* some preventative measures taken. > > AFAIK, the only *big* public time services that do leap-smearing are > Google & Amazon. > > Yes, I know a person *can* configure their own NTP server to do > smearing too But if that one second is mission critical, then you > are probably taking a lot more care choosing upstream time sources. > > ___ > 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] can of worms: time-of-day in a community radio station
> You can't test a server for smearieness. It wouldn't surprise me if some of > them turn out to be getting time from google servers or something similar. True, but you *can* see which upstream time source has been selected for a NTP server. Ask went through the pool servers last leap-second and contacted all the owners that were returning a Google IP as their primary time source to get them to change their configuration. Likewise, said servers that weren't reconfigured in time were pulled out of rotation during the event to prevent any issues. So there *were* some preventative measures taken. AFAIK, the only *big* public time services that do leap-smearing are Google & Amazon. Yes, I know a person *can* configure their own NTP server to do smearing too But if that one second is mission critical, then you are probably taking a lot more care choosing upstream time sources. ___ 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] Flash!!! FA2 works on Arduino Tablets !!!
On Mon, Oct 21, 2019 at 12:01 AM Didier Juges wrote: > One issue: once the tablet is connected to the FA2, there will be no way to > charge the tablet, so start with a fresh battery... I would think that if you connected both the FA2 and the tablet to a USB hub you should be able to talk to the FA2 as well as maintain the tablet's battery. Of course this requires that you select a USB hub which can deliver enough power to the tablet, but that shouldn't be too difficult. -- paul moore www.paul-moore.com ___ 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] can of worms: time-of-day in a community radio station
Regarding analog clocks, what is the groups opinion on these Atomic WWVB Signal Radio Controlled Clock Movements? I ordered one from China but it isn't here yet. I am hoping that I won't have to change the clock for DST. They are only $15. https://www.klockit.com https://www.amazon.com/dp/B07XWTMZZD/ref=cm_sw_r_tw_dp_U_x_VJARDbHBEE15J https://www.aliexpress.com/item/33005680618.html -- Myron ___ 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] Flash!!! FA2 works on Arduino Tablets !!!
I have no way to test this, but I wonder if one can charge the tablet wirelessly while the USB port is in use. Assuming the tablet is capable of wireless charging in the first place. -Pat (KG5YPQ) On Sun, Oct 20, 2019 at 11:01 PM Didier Juges wrote: > The interface from the FA2 is USB, so there is no need (and no way) to go > through a DB9. I recommend using an adapter to go from your tablet > (typically micro-USB or USB-C) to a USB-A socket, then use a standard USB-A > male to USB-B male cable going to the FA2. > > One issue: once the tablet is connected to the FA2, there will be no way to > charge the tablet, so start with a fresh battery... > > The app keeps the screen activated as long as the battery is >50%. After > that, Android will put the app to sleep and recording will stop and the > data that is not saved will be lost. There are a number of ways to deal > with that, I am waiting to see actual use cases to come up with the best > way. The battery life limitation is clearly an issue. > > You can buy cables that have a charging port but they only power the target > (the FA2 in this case), not the tablet. I believe that you cannot charge > the battery when the USB port is used as a master because as a master it is > intended to deliver power, not receive it. > > Didier KO4BB > > On Sun, Oct 20, 2019, 10:19 AM Jim Harman wrote: > > > Didier, > > > > This looks very useful. Is there a specific DB9 to USB-C cable that you > > would recommend, or would you use a USB-A (female) to USB-C adapter with > a > > standatrd USB-A to DB9 cable? > > > > > ___ > 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.
