Re: [time-nuts] time-nuts Digest, Vol 180, Issue 22
From: Bob kb8tq >>>> - high-Q crystals require SC-cut >>> ... An SC has a lower Q than an AT of similar size >>> and design up to the point acoustic Q losses completely take over. >>> If you are talking about sub 20 MHz OCXO?s with ?doable? crystal >>> package sizes, the AT will have the higher Q by a significant margin. >> >> Could you please back up this claim with verifiable facts? > > Order up a few 5 MHz 3rd overtones in HC-40 packages and see what you get. > You also could send in an RFQ for a batch of each to any of the people who > make them > and see what comes back. > Bob Here is a random selection of links to back my point of view that, if you have noticed, contradicts Bob's. If anybody is interested they will find information themselves without much effort. I suggest printed books if you don't trust Internet at large. http://www.crovencrystals.com/croven_pdf/Old%20Spec%20Sheets/croven_catalogue.pdf (Croven Crystals is Wenzel company) The main advantages of these resonators, and in particular the SC-cut type are: higher Q-factor (typically 10 - 15% better than equivalent AT-cut resonators) https://www.tfc.co.uk/pdfs/SC_cut_crystals_article_TFC.pdf SC cut family of quartz crystals: Other key characteristics include Higher Q factor https://www.rfwireless-world.com/Terminology/AT-cut-vs-SC-cut-quartz-crystal.html Specification:Q factor AT cut: lower SC cut: higher (it will achieve low phase noise) http://members.femto-st.fr/sites/femto-st.fr.patrice-salzenstein/files/content/Peer-review-journal/smdo160017.pdf SC-cut It has faster higher Q, warm-up speed and better phase noise close to the carrier. http://www.resonal.com/Downloads/John%20R.%20Vig%20-%20tutorial%20on%20Quartz%20Crystals%20and%20Oscillators.pdf Advantages of the SC-cut: Higher Q for fundamental mode resonators of similar geometry http://www.mtronpti.com/sites/default/files/files/crystal-resonator-terminology.pdf A typical 10 MHz, 3rdovertone SC may have a Q of 1.0 to 1.3 million; a 100 MHz, 5th overtone AT may have a Q of 80 to 100 thousand, while a 100 MHz AT fundamental would be much lower, in the range of 20 to 50 thousand. https://www.eetimes.com/document.asp?doc_id=1290592# (MptronPTI) Since SC-cuts have a much higher Q-factor than AT-cuts, SC-based OCXOs offer better noise performance from 1-Hz offset to 1,000-Hz offset. Worryingly, I have started receiving unpleasant personal emails from list members suggesting that I do not question factual correctness of other's opinions. This will explain why I am going off the list for the sake of everyone's good. Leo Bodnar ___ 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] Advantages of GNSS ???
> Well part of it comes from designing, testing, and manufacturing a few > thousand OCXO designs over the years. We likely built 10’s of millions of > OCXO’s over the time I was doing / managing that. It might be just my personal opinion but credential swinging is better left out of technical discussion. > > - high-Q crystals require SC-cut > ... An SC has a lower Q than an AT of similar size > and design up to the point acoustic Q losses completely take over. > If you are talking about sub 20 MHz OCXO’s with “doable” crystal > package sizes, the AT will have the higher Q by a significant margin. Could you please back up this claim with verifiable facts? Leo ___ 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] Advantages of GNSS ???
Hello, Why would you not want high drive level for best close-in noise? This is at odds with general thinking in the industry. Close-in in this context means from 0.1Hz to 1/f knee which is 1-100kHz depending on the design of the sustaining amplifier. There are few reasons why low phase noise "practical" oscillators are built as OCXOs: On one hand: - close-in noise depends on 1/f knee frequency - lowering knee frequency requires high-Q resonators - for classic 1MHz..100MHz range this means crystals - high-Q crystals require SC-cut On the other hand: - phase noise density is measured as a ratio referred to carrier level - increasing carrier level improves phase noise figure - increasing carrier level necessitates increasing drive level - maintaining reasonable ageing rate at higher drive levels requires SC-cut crystals Having established that SC-cut is preferred: - SC-cut has high temperature turning point. Its room temperature tempco is much worse than AT-cut's one making it mostly unusable as XO or TCXO - High temperature turning point requires oven Leo >> From: Bob kb8tq > It depends a lot on the offset you are looking at. For close in phase noise, > you probably don’t > want high drive. If you are only after phase noise past 10KHz, you may not > want / need > an OCXO in the first place. Selecting crystals (like one in a hundred) for > very high drive / > low phase noise setups *is* done. It’s just not very practical. > > > On Jul 10, 2019, at 3:49 AM, Leo Bodnar wrote: > > It depends whether OCXO is designed for long term stability and low ageing > > or low phase noise. > > Low ageing requires low drive but low phase noise needs as much drive as > > humanely possible - often approaching mW levels. ___ 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] Advantages of GNSS ???
I did, sorry, - it was a finger slip. Now, what I find kind of funny is that one of the meanings of "monotonous" is "repetitious or periodic" which is almost exactly the opposite of monotonic. Leo > From: "David G. McGaw" > Leo - > I do believe you mean non-monotonic, rather than non-monotonous. Not > being monotonous is a good thing.? :-) > David N1HAC ___ 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] Advantages of GNSS ???
> From: Bob kb8tq > Drive power on an OCXO will pretty much always be below a milli-watt. A > typical design will be in > the range of 1/10 to 1/100 of that power level. It depends whether OCXO is designed for long term stability and low ageing or low phase noise. Low ageing requires low drive but low phase noise needs as much drive as humanely possible - often approaching mW levels. Leo ___ 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] Advantages of GNSS ???
It's not very good, it is highly non-linear and even worse - nonmonotonous. It sometimes produces runt pulse glitches when you roll time backwards. I have used them in GPS clocks for many years but never enabled them for end user mode. It's really a very primitive delay line series and I don't regret seeing it gone. On top of this it is Maxim, doh! Leo Chris Caudle wrote: > The original is not, there is a close variant still in production: > > https://www.maximintegrated.com/en/products/analog/clock-generation-distribution/DS1124.html > > "The DS1124 is an 8-bit programmable timing element similar in function to > the DS1021-25. The 256-delay intervals are programmed by using a 3-wire > serial interface. With a 0.25ns step size, the DS1124 can provide a delay > time from 20ns up to 84ns with an integral nonlinearity of ±3ns. " > > Small package, would be a little difficult to prototype by hand, but not > impossible. > > -- > Chris Caudle ___ 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] Advantages of GNSS ???
Bob, what are you calling "time correction"? You are now quoting F9T which is not the product original statement related to (F9P.) If you refer to internal Ublox adjustment of instantaneous timepulse train then it is performed at navigation rate - up to 20Hz on F9P. F9P's rate of TP can be set from 0.25Hz to 10MHz according to the datasheet but in reality is usually wider. TP edge quantisation is a separate issue to TP base rate adjustment and it is done at TP rate. Leo > Subject: Re: [time-nuts] Advantages of GNSS ??? > They go absolutely crazy updating nav?.. but they only come up with the > timing correction once a second. > > From the latest version of the F9T Manual UBX-19005590 - R02 on page 43: > The recommended configuration when using the UBX-TIM-TP message is to set > both the measurement rate (CFG-RATE-MEAS) and the time pulse frequency > (CFG-TP-*) to 1Hz. > > Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP > message can appear between two pulses if the time pulse frequency is set > lower than 1 Hz. In this case all UBX-TIM-TP messages in between a time pulse > T1 and T2 belong to T2 and the last UBX- TIM-TP before T2 reports the most > accurate quantization error. In general, if the time pulse rate is not > configured to 1 Hz, there will not be a single UBX-TIM-TP message for each > time pulse. > > Sorry if the quote comes through a bit garbled. Sometimes this cut and paste > stuff does not quite do the trick. > Indeed it?s not 100% clear what they are doing from the docs. They say this > and that here and there. The > bottom line is still that you can only trust the sawtooth offset data to be > correct at the one second point. > > Bob ___ 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] Advantages of GNSS ???
Correction on all Ublox receivers including F9P is done at navigation rate which can be set as high as 20Hz. Leo > From: Bob kb8tq > Frequency of any GNSS output on the F9P is limited by the accuracy of the > time pulse. > Correction is only done once a second. ___ 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] Aerial coax downlead placement
In a (almost) ideal coaxial cable (almost) *all* RF electromagnetic field is inside the cable. Unlike ladder balanced transmission line where it is everywhere else in the universe. Leo > From: Peter Vince > sure of the best advice to give him. I'm sure I heard that you should > never drop the coax down the middle of your support-pole, as the conducting > pole will mess up the characteristics of the cable by affecting the > currents in the outer braid. ___ 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] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design
Hi Dana, I am just saying that, properly implemented, PLL and FLL are indistinguishable as long as output signal is concerned while lock is present and that the phase slew at regaining lock in PLL loop is counterproductive for one but necessary evil for others. I have a feeling that FLL is looked down upon by general public ever since PLL became a household term. In a well designed PID loop "I" term makes sure that you don't have "permanent but varying error." All my messing about with loops, holdovers and recovery was pretty much with your application in mind. Cheers! Leo > Are you saying that you want to abandon phase lock altogether in favor of freq > lock? Or just during the reacquisition following loss of and restoration of > the > reference? > > By me definition of pure freq lock, there will generally be some permanent > (but varying) > frequency error, so that phase error could accumulate without limit; > clearly an undesirable > thing in most applications. > > My interest lies in having a stable LO for receiving, without accumulating > phase error (at least during times of missing reference). When the reference > goes away, I'll > accept some phase error accumulation. So for me, I think the best approach > is phase lock > under normal circumstances, but switch to freq lock during reacquisition of > phase lock. > > DanaK8YUM ___ 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] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design
Hi Karl, I will work on better website description. There are few loops in the device - GPS reference is PLL and the synthesiser is now FLL (used to be PLL.) Leo > Hi, Leo. The web pages for your precision frequency references say they use > PLL. Is that just for frequency generation, and you use FLL for resyncing? > Karl ___ 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] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design
I have to draw your attention to practical aspects of why some designs use FLL rather than PLL. Consider a GPS locked OCXO outputting GPS synced 10MHz signal. Properly designed control loop will not produce much (if any) difference when the reference (GPS signal) is present. In the end, integral of zero is zero. When reference (GPS lock) is lost the things are very similar too, holdover is just flying blind in the rough direction you were facing last. Accumulating frequency and phase offset on the way. However, when reference is restored the things are much different. After regaining the reference (which in case of GPS signal has unambiguous absolute time embedded into its phase) *proper* PLL loop will try to correct for slipped phase at the highest slew rate. This can be huge. If phase has drifted 1ms apart the loop will have to slew the phase all the way until it gets those 10,000 cycles out of the way. This usually looks ugly in frequency domain and is very disrupting if you are using the device as frequency reference rather than an absolute time reference. Proper FLL loop will just gently (and reasonably quickly) get your frequency back and forget about all the lost phase. Which is what a lot of users want. Initially, I have used PLL mode on GPS clocks that I am making, but switched over to FLL during the last few years. Cheers Leo ___ 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] LeoNTP PPS output to PC DB9 input
LeoNTP uses short-circuit tolerant LVCMOS driver with 3.3V level output. > Does the LeoNTP BNC output come up in the last configured state? Of course it does. Leo ___ 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] GPS 1PPS, phase lock vs frequency lock, design
Apologies, teletype did not let the picture through http://www.leobodnar.com/files/2x%20ECOC%203v6.png > I had half a dozen of 38.88MHz ones for tinkering. > There is nothing exciting about them apart from a noisy LDO which has peaking > around 70kHz. > Spurs are mine. > Leo ___ 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] GPS 1PPS, phase lock vs frequency lock, design
I had half a dozen of 38.88MHz ones for tinkering. There is nothing exciting about them apart from a noisy LDO which has peaking around 70kHz. Spurs are mine. Leo On 25 May 2019, at 17:00, Gerhard Hoffmann wrote: > Has anybody out there more information about this oscillator? > Its data sheet is thinner than a cookbook from the Sahel zone. > No phase noise data @ 100 MHz??? I've got one of them last week. > https://www.digikey.de/products/de?keywords=xc2265-nd > regards, Gerhard ___ 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] Rooftop antenna and splitter
> From: Denny Page > Initially, the units were connected to puck antennas that are literally side > by side. At approximately 19:15, the units are taken off the puck antennas > and connected to the single antenna through the splitter. > I really didn?t expect such a dramatic change. It does look significant, with difference dropping to what looks like about 5ns rms. I thought most of the timing noise is coming from network performance/topology but it does look like it is GPS performance related. > From: Bob kb8tq > There normally is a ?survey in? process on a GPSDO. The location then gets > used to This particular time server does not use survey-in mode. Leo ___ 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] OCXO Question
UUCP or Maximus BBS software ate the attachment. http://www.leobodnar.com/balloons/files/UCT-OSA-MY%20108663-01%20.png Leo On 27 Apr 2019, at 17:00, time-nuts-requ...@lists.febo.com wrote: > Subject: Re: [time-nuts] OCXO Question > > I bought half a dozen to measure their PN for somebody else - there is > nothing special about them on that front. > Later on I ripped them open and they were both double oven and unused - like > advertised. > Being cheap and ubiquitous is the only thing special about them... Or is it? > Leo > > >> From: Dan Rae >> ...How close they are in performance to an original 8663 I have no idea, but >> look forward to finding out. > > ___ 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] OCXO Question
I bought half a dozen to measure their PN for somebody else - there is nothing special about them on that front. Later on I ripped them open and they were both double oven and unused - like advertised. Being cheap and ubiquitous is the only thing special about them... Or is it? Leo > From: Dan Rae > ...How close they are in performance to an original 8663 I have no idea, but > look forward to finding out. ___ 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] Garmin GPS12XL V3.51
Assume that the device does not have any reliable long term non-volatile memory that you can update. In the absence of any clues your only reliable piece of knowledge is that the cold start date is somewhere after the date of manufacturing or, most often, firmware compilation date. This is the simplest strategy - one that provides 20 years of device lifespan. "Device" in this case can be anything, including a single chip module that only has mask ROM and 128bytes of OTP memory like most Ublox modules. If you have NVRAM, you can store last seen full week number periodically. Unless you don't power up the device for 20 years since last update you should be fine too. Of course, if you have the ability to decode CNAV messages you can kick the can much further down the road. Leo > From: Joe Leikhim > My question is this. Why would the receivers be hard coded to a start date > for the 1023 week register? > Why doesn't the receiver restart that date whenever reset or turned on after > a period of time? > It seems like faulty logic to build in a defect like this. ___ 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] multimeter
Based on your requirements I would recommend an orange one. Leo > From: Jim Palfreyman > Hi all, > I think I'm in the market for a new digital multimeter. > Could I have some recommendations? > 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] Yet another GPSDO project.
Tobias, Have you measured resulting phase noise of the finished unit? Thanks Leo > From: Tobias Pluess > sure, I believe you since my primary requirement was phase noise. This is > because I'd like to use the OCXO as reference for my spectrum analyzer and > also for my HP 8663 signal generator to do phase noise measurements ___ 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] Synthesized Signal Generator query
Fluke 96040A disagrees from the back bench. Leo > From: Tom Knox > Much more expensive, but in a class by itself is the Rohde SMA100A option B22. ___ 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] Synthesized Signal Generator query
E44xx-AP/DP are a bit rubbish in PN department. I have tested a few units at 1GHz and the results were within 1-2dB from the datasheet, so have a look there. Don't even bother with -A/D models. If you are looking for HP 8664A/8644B class performance, have a look at IFR/Aeroflex/Marconi 2041 and 2042. Yes, they sometimes can be had for $1000. Leo > From: "Don@True-Cal" > I have my sights on an HP 8664A with Opt. 004 Low Phase Noise and want to > keep the purchase around $1000... > Can anyone give me advise on any similar low phase noise source that > is not so big and heavy. I like the looks and size of the E44xx series but > do they come even close to the signal purity of the 8664A. ___ 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] Auto-fail-over switch
Would this work? http://www.wenzel.com/wp-content/parts/501-09371.pdf I have few of these, they have good enough PN to be used as run-around reference source for measurements: http://www.ebay.com/itm/16307191 Leo > From: Jeff Blaine > > Wondered if anyone had seen some sort of gadget that would look to see > if there was a 10 Mhz signal and switch a relay (or provide some other > output) in the absence?? I would like to cook up some sort of fail over > switch without having to do much actual work. :) ___ 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] Ublox F9P multi-band GPS receiver
Considering that Ublox won't even sell the stock part unless you are willing to buy 100,000 units I doubt they will listen to anyone representing several dozen hobbyists. Their biggest argument for having 100k MOQ is "we are afraid that you will need support." I would say (without much factual backing) that you have to be buying a few millions devices before they will even listen to what someone have to say about additional features. I am ready to hear success stories but my official Ublox experience so far was nothing but frustration. So now, when I need Ublox silicon I buy it from Alibaba for $1 (including occasional fakes that have no silicon inside) rather than for $5 from Ublox themselves - because they won't sell 6,000 I need. When I need features support - I write my own patches. It's ironic that the most knowledgeable guy on Ublox support forum is not even affiliated with the company. Their products are amazing for what they cost but I'll switch at a drop of a hat when something worthy comes along. Leo > From: Bob kb8tq > If you are a customer who is buying a ton of these a month, give uBlox a call > and they will > likely listen to you as they come up with the next generation. In terms of > changes to this > generation, suggestions are a couple years too late. The silicon is already > out of the fab > and it?s many millions of dollars to re-shoot those masks. >> On Jan 25, 2019, at 9:58 PM, MLewis wrote: >> So if there's someone they'd listen to, it's not too late to see if there's >> features from the various time-nuts F9P posts that ublox would add? ___ 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] Ublox Neo M8T no output on TP2 question please?
I have mislead you about NEO-M8T-0-10 TP 2 capabilities, sorry. https://www.u-blox.com/sites/default/files/products/documents/NEO-LEA-M8T_ProductSummary_%28UBX-16000801%29.pdf does not differentiate between two outputs and lists range as 0.25Hz-10MHz. Regarding flash/no-flash bootleg versions - mask ROM firmware residing on the die does not support FTS functions (there is not enough space for extra features and increasing the die size would increase base product cost) so if you have FTS product then it must have flash inside to run the code from. Whether this flash IC is of adequate size to accept future updates or whether its erasing and writing is supported by the main firmware in ROM is a separate question. It is technically possible to create operational but non-upgradeable FTS product . Leo ___ 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] Ublox Neo M8T no output on TP2 question, please?
Hi Chris, By query I meant poll settings, sorry. Your screenshot shows 1MHz configured on TIMEPULSE 2. I don't think it is going to work. Standard products used to have 1kHz frequency limit on TIMEPULSE 2. I have not checked any FTS functionality recently. The manual (Receiver Description) says... "In current FTS products only TIMEPULSE 2 can be used for pulse generation. Additionally, just 0.5Hz, 1Hz and 2Hz time pulse output is supported by current FTS products. Other output frequencies may be configured with UBX-CFG-TP5 but are not guaranteed to work properly." You will notice that the example in the same manual [confusingly] shows TIMEPULSE 2 set to 10MHz. Thanks Leo > From: Chris Wilson > > http://www.chriswilson.tv/ublox/TP2.jpg > > ___ 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] Ublox Neo M8T no output on TP2 question, please?
Chris, Check that you have configured the pulse width and period/frequency switches correctly. Please post the result of UBX-CFG-TP5 query on TIMEPULSE2 here. If you are putting Ublox into SAFEBOOT mode you'll see it right away - all navigation tasks are shut down in this mode. Leo > From: Chris Wilson > I have a Ublox NEO-M8T-0-10 that in the OE state shows no output on > TP2. If I programme it with the UCentre software for say 500hZ output > I sill see nothing on TP2. Do I need to pull it high on boot or > anything to see an output please? I am not probing it with a X10 scope > probe until after it has booted, so I don't believe it's pulled low on > boot, although I can't see how a X10 probe setting could pull it > anyay. TP0 behaves normally and accepts changes in output frequency. > Otherwise it also seems to generally act correctly. Thanks ___ 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] Short term 10MHz source (and unrelated comment)
Magnus, I am very sorry for speaking out of turn. Few messages earlier you have referred to the raw PPS and I thought I might offer an insight to what is happening inside Ublox chipset hardware that is otherwise not know to vast majority of its users, including most members here. I only speak up when I think I can offer something others cannot. Perhaps, I should have quoted your other message. Perhaps, I should have just continued reading instead. > From: Magnus Danielson > For some GPSDOs you get a PPS and is "raw" from GPS module and not > resynthesized from the steered 10 MHz. > Now, if one uses this PPS it would get quite a bit of noise, but if one was > to measure that noise against the smoothed 10 MHz with a separate TIC/TICC > one should be able to use the PPS as a transfer oscillator with > the right rate but get close to the smoothed 10 MHz as stability. > From: Magnus Danielson > Recall that the quantization is really a form of time-stamp value for > the channel in it's relation to the time-base. It's a systematic pattern > in the time-base clock and it is phase-locked to the time-base phase. > ... > So, to conclude, the quantization noise that we have is very systematic > in its nature, > On 1/9/19 10:10 AM, Leo Bodnar wrote: >> Depends what you call "systematic"... > > From: Magnus Danielson > Leo, > Now, what I was talking about was frequency/time-interval counters in > this case, not GPS-chips or GPSDOs. So, your comment seems out of > context in that regard. I feel increasingly uncomfortable posting here as one gets subtly condescending remarks from celebrated members of what comes across as an elite club of few dozen intellectuals discussing same few topics in rounds. I am only mentioning this in light of TVB's unexpected post on EEVBlog (which is at the other extreme of creative engineering community) that seemingly invites new members to join the list. These two establishments can't be further apart in their culture and average knowledge level and I am fascinated to see what might happen as a result. Thanks Leo ___ 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] Short term 10MHz source
Depends what you call "systematic"... I can only speak for Ublox but it is fairly representative of modern (even though its architecture did not change for almost 10 years) GPS chipsets. The quantisation runs off internal cheap XO or TCXO that is PLLed to produce MCU core clock that is then phase-accumulation quantised to the current navigation solution target - typically every 1-10Hz. Stock Ublox has 26MHz XO/TCXO which is then PLLed by MCU core into system 48MHz clock which runs the Cortex core - including timers - that produce 1PPS TP. Somebody measured Ublox 1PPS against the stable timebase and looked at same Ublox reported quantisation correction (ps order of magnitude) and actual error was about 1ns order of magnitude. This would be unaccounted discrepancy of what Ublox thinks is happening on its 1PPS I/O pin and what is actually there. This makes analogue delay line correction only viable to that level of accuracy. Whether this inaccuracy is the result of a high core PLL phase noise, sloppy quantisation algorithm or hardware I/O drivers is an interesting academic question but won't solve the problem. Ublox core can run off many external clock frequencies from 12 to 40MHz but they all will go through the PLL which makes it pointless to experiment with. Leo > From: Magnus Danielson > > Recall that the quantization is really a form of time-stamp value for > the channel in it's relation to the time-base. It's a systematic pattern > in the time-base clock and it is phase-locked to the time-base phase. > ... > So, to conclude, the quantization noise that we have is very systematic > in its nature, ___ 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] HP3325B as LO for a transceiver or receiver?
There are no detectable spurs on this plot within 100kHz from the carrier. I have spent a lot of effort trying to get rid of the spurs while maintaining low phase noise. Here is how it looked before the spur war http://www.leobodnar.com/files/miniGPS%20clock%20-%20old%20design.png Leo > From: "Chris Caudle" > On Wed, January 2, 2019 4:15 am, Leo Bodnar wrote: >> Here is the phase noise at 10MHz >> http://www.leobodnar.com/files/mini%20GPS%20clock%20-%20phase%20noise%2010MHz.png > Does that plot have enough resolution to show any narrow band spurs? That > looks really clean for a programmable clock source. ___ 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] HP3325B as LO for a transceiver or receiver? Phase noise?
Here is the phase noise at 10MHz http://www.leobodnar.com/files/mini%20GPS%20clock%20-%20phase%20noise%2010MHz.png There will be overall noise increase of about 4dB at 15.6MHz Leo On 1 Jan 2019, at 17:00, time-nuts-requ...@lists.febo.com wrote: > From: Mark Goldberg > Leo Bodnar's GPSDOs do provide good enough phase noise output. > I'l let him provide recent data if he wishes. You could feed it similarly > to how I feed an external frequency to my Perseus SDR, documented on my web > pages. > On Tue, Jan 1, 2019 at 7:24 AM Chris Wilson wrote: >> Could I use my HP3325B locked to a Trimble Thunderbolt GPS disciplined >> 10MHz oscillator as the master LO of my Kenwood TS-590S transceiver >> that has a LO at 15.6 MHz ___ 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] New GPS Interface Specification IS-GPS-200J is out
Hi, For those who missed it - IS-GPS-200 has been updated a few months ago. https://www.gps.gov/technical/icwg/IS-GPS-200J.pdf Leo Bodnar ___ 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.
