[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

HI We’re not building a synthesizer here. We are putting together a simple piece of test gear. The purpose of the test gear is to measure phase noise down into the -170 dbc / Hz range ….. Bob > On Jul 12, 2022, at 4:05 PM, Mike Monett via time-nuts > wrote: > >

[time-nuts] Re: GPS failed

Hi The “typical” Symmetricom cone shaped GPS antennas are targeted at cell phone tower applications. Being mounted on the same structure as multiple cell transmitters puts them in a significant RF environment. They have a *lot* of filtering built into the antenna to try to prevent overload

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)

Hi If you have any ceramic capacitors in the mix, they are often microphonic. The X7R versions are typically the best “high C” types. NPO’s normally are completely non-microphonic. Other non-ceramic caps should be ok, but who knows. Roughly speaking, 1 nV / Hz should be low enough to not

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)

Hi There are a very small number of signal generators that *might* help when measuring phase noise on a good source. The “rest of them” are very much in the “don’t bother” category. Just which one is in the “maybe” category depends a lot on your frequency of interest. None of them seem to be

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

11, 2022, at 8:05 AM, Mike Monett via time-nuts > wrote: > > To Bob kb8tq > > Figure Of Merit sounds like a useless number. I have a different > approach that yields immediate and useful results. Before I explain > my method, let me introduce myself. >

[time-nuts] Re: GPS failed

Hi These days there are folks who make a living tracking down interference sources in the vicinity of ports and airports on a contract basis. Many of the issues are navigation related. Some of it is GPS. Some is other stuff ( like 5 GHz WiFI and radar …) Bob > On Jul 11, 2022, at 1:28 PM,

[time-nuts] Re: GPS failed

Hi Are all the receivers the same type / model? If so what are they? Various receivers made over the last 20 years have some “issues” that can pop up. Is the antenna gain properly matched to the needs of the receiver? Some are designed for a “target gain” of 20 db, others 30, some 50. Match a

[time-nuts] Re: dual supplies Re: Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi I seem to recall TI having similar parts. The big gotcha is tossing large chunks of C onto the ground to rail connections. A typical op amp is not at all happy with this. Bob > On Jul 10, 2022, at 5:48 PM, Richard (Rick) Karlquist via time-nuts > wrote: > > > > On 7/10/2022 10:14 AM,

[time-nuts] Re: What about the frequency discrimination method? (offshoot from DIY PN analyzer)

Hi If you dig into the various books on phase noise, they do go into other ways to measure it. The bottom line is that things like frequency discriminators are quite noisy (floor wise) compared to a single mixer. Bob > On Jul 10, 2022, at 10:26 AM, ed breya via time-nuts > wrote: > > Hi

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi There’s really no need to use the Vref out of the OCXO at all. Since many devices don’t have one, you will need a “replacement” at some point. Simply pulling the “set reference” off of a cleaned up output of your main supply(s) is typically how it is done. The most basic reason to not hard

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi Pretty much the best mixer to use for this in a basement / DIY basis is a Mini Circuits RPD-1 or one of it’s siblings. It has a 500 ohm output on the mix port instead of 50 ohms. Yes, you open circuit terminate it ( so 5K ) but as noted, it’s the Zout of the mixer that likely sets what the op

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi Yes it is a pain to implement dual supplies. I ponder that issue every time I build one of these setups. I’ve built a lot of them …. If you are going to do a single supply, setting up a “virtual ground” is probably the best way to go. Do it with a drive circuit to provide very clean 15V off

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi (see below) > On Jul 9, 2022, at 12:06 PM, Erik Kaashoek wrote: > > Getting the simple PNA to lock was a bit difficult due to the overly > simplistic translation of the mixer output to the Vtune of the OCXO > To get some more flexibility I added a summing opamp that summed the mixer >

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

stuff does not really apply to a DBM approach, you would never see this done. One works one way, the other works in a very different fashion. Bob > On Jul 8, 2022, at 8:19 PM, Mike Monett via time-nuts > wrote: > > To Bob kb8tq. You wrote: > >> Hi > >> The nois

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

HI > On Jul 8, 2022, at 7:44 PM, Mike Monett via time-nuts > wrote: > > To Erik: > > ……. > Another item that might be of interest is the PFD. The Hittite > HMC984LP4E has -231 dBc/root(Hz) of noise, which is quite low. The > datasheet is at >

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi > On Jul 8, 2022, at 10:35 AM, Mike Monett via time-nuts > wrote: > > Bob, you wrote: > >> Mike. One concern I have with active components as mixer is noise. >> For an SA I designed only a passive DB diode mixer had low enough >> output noise. Would a PF detector as being an active

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

n be found here: > http://athome.kaashoek.com/time-nuts/Measuring_phase_modulation.pdf > Written by Bob Nelson from Keysight. > Very helpful presentation for people (like me) that are new to all this. > Erik. > > On 8-7-2022 18:58, Bob kb8tq wrote: >> Hi >> >> Like it or not, the mixer

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi Like it or not, the mixer is a non-linear load. It also has a frequency dependence. Even with “saturation” levels, the slope can and does change. That’s the short list, as you dive into it, things get even more complex in terms of “might be” sort of issues. How can you be in saturation and

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Since signal generators are not likely to get you to the same sort of noise levels as a very good stand alone source, you very much do not typically want a signal generator involved in a real measurement. Yes, there are always exceptions to any blanket statement … Bob > Erik. > &g

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi One consideration: If you do signal injection for calibration, you have the amplitude uncertainties on both the “carrier” and injected signals. The slope at zero on the beat note is likely to be *much* more accurate ( even if gain measurement at audio gets thrown in …) Bob > On Jul 7,

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi The idea is partly to lock the two devices. The bigger objective is to hold the mixer output at the correct zero volt operating point. Cabling things to a different device and then doing phase correction to keep things at zero would be a major pain. Bob > On Jul 7, 2022, at 5:52 AM, Mike

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi Yes, you do need to know the system gain. Since we are talking about gain at audio, measuring the gain directly is not a crazy thing to do. One of the things that makes audio spectrum analyzers a nice tool for this that they eliminate the “variable gain to the sound card” issue. Some sound

[time-nuts] Re: Isolation amp transistors

Hi > On Jul 7, 2022, at 12:09 AM, Gerhard Hoffmann via time-nuts > wrote: > > Am 2022-07-07 7:22, schrieb Bob kb8tq via time-nuts: >> Hi >>> On Jul 6, 2022, at 1:53 PM, Richard Karlquist via time-nuts >>> wrote: >>> The 2N5179 has high b

[time-nuts] Re: Isolation amp transistors

ion with a vaccuum tube cascode than a solid > state cascode ? > > -glen > > On 07/07/2022 15:22, Bob kb8tq via time-nuts wrote: >> Hi >> >>> On Jul 6, 2022, at 1:53 PM, Richard Karlquist via >>> time-nuts wrote: >>> >>> The 2N5

[time-nuts] Re: Isolation amp transistors

Hi > On Jul 6, 2022, at 1:53 PM, Richard Karlquist via time-nuts > wrote: > > The 2N5179 has high base spreading resistance (decreases isolation). As does sticking a resistor (even a small one) in series with the base …. Yes, inductance is even worse. For “best isolation” in a cascode you

[time-nuts] Re: Should a double oven XO be thermally isolated or just draft protected?

Hi Unless you measure the change of the device over a controlled temperature range ( like 0 to 70C ) at a controlled rate ( like < 0.1C / minute ) it’s hard to know if this or that restriction / insulation on an OCXO has “upset” its temperature compensation. If you “make the heater work half

[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik Kaashoek)

Hi > On Jul 5, 2022, at 9:00 AM, Erik Kaashoek via time-nuts > wrote: > > Mike. > One concern I have with active components as mixer is noise. For an SA I > designed only a passive DB diode mixer had low enough output noise. Would a > PF detector as being an active component, not create more

[time-nuts] Re: DIY Low offset Phase Noise Analyzer

0dBm/Hz around 10 MHz is cheap on eBay. Calibration can > be done with any SA having noise markers. > > On Tue, Jul 5, 2022, 21:34 Bob kb8tq mailto:kb...@n1k.org>> > wrote: > Hi > > One of the “gotcha’s” with this is the need for dual supplies. That’s what > lets yo

[time-nuts] Re: DIY Low offset Phase Noise Analyzer

Hi One “cute trick” that can be done on the lowpass filter: Ideally you would like to terminate the mixer properly at the DUT and DUT x 2 frequencies. Open circuit (or short circuit) is ok at audio. The quick and easy way to do this is to put an appropriate resistor ( 50 ohm, 500 ohm, whatever

[time-nuts] Re: DIY Low offset Phase Noise Analyzer

wrote: > > Bob, See below > Thanks. > Erik. > > On 5-7-2022 19:37, Bob kb8tq wrote: >> Hi >> >> One “cute trick” that can be done on the lowpass filter: >> >> Ideally you would like to terminate the mixer properly at the DUT and DUT x 2 >>

[time-nuts] Re: DIY Low offset Phase Noise Analyzer

Hi If you need that sort of isolation, it certainly can be done. NIST has papers on very simple / DIY compatible cascode amps that will do the trick. ( chain of common base stages driven by a common emitter). Some folks on the list have gone a lot further in terms of complexity than NIST did.

[time-nuts] Re: Silicom PCIe timestamping network cards

Hi > On Jul 4, 2022, at 10:04 AM, Poul-Henning Kamp via time-nuts > wrote: > > > Poul-Henning Kamp via time-nuts writes: > >> The timestamping counter gets its clock from the ethernet line >> signals, and the counting frequency therefore depends on the ethernet >> speed: >> >>

[time-nuts] Re: Silicom PCIe timestamping network cards

Hi I think the key parameter is the 8 ns resolution on the time stamp. That may or may not be adequate for this or that application. Without doing a deep dive on the part, it’s not real clear how they deal with the accuracy of the onboard timebase. It’s rated at 0.01 ppm with no real details.

[time-nuts] Re: DIY Low offset Phase Noise Analyzer

Hi If you are running a high gain op-amp to buffer things into a sound card *and* using the same op-amp output to drive the EFC, then you will have problems. Simple answer is to use a couple of op amps. Buffer the mixer with something low noise. Get the output of the mixer up to the point it

[time-nuts] Re: Should a double oven XO be thermally isolated or just draft protected?

Hi If you tear into *lots* of HP devices with OCXO’s in them (not just the 10811 version), the most typical place for the OCXO is right. next to the power supply. That puts it inline with the output of the fan. Why? The OCXO gets hot. Heat buildup in the instrument is not a good thing. They

[time-nuts] Re: Should a double oven XO be thermally isolated or just draft protected?

Hi Modern OCXO’s are set up based on temperature run data. They play with set point (and possibly electrical gain) to optimize the TC contribution of the crystal *and* the rest of the parts in the device. This is true of single and double ovens. One not so obvious point is that these runs are

[time-nuts] Re: What's the best HP OCXO for frequency counter reference?

Hi > On Jun 28, 2022, at 12:15 PM, Hal Murray via time-nuts > wrote: > > > Adrian Godwin said: >> If you use the ovened oscillator for temporary use away from the home GPSDO, >> how good will the oscillator be with those interruptions to power / >> temperature, and will it stabilise during

[time-nuts] Re: What's the best HP OCXO for frequency counter reference?

is a “good one”. Stuff happens over time …. subtle changes rarely get noticed. Bob > On Jun 28, 2022, at 12:03 PM, Dr. David Kirkby > wrote: > > On Tue, 28 Jun 2022 at 20:04, Bob kb8tq via time-nuts > mailto:time-nuts@lists.febo.com>> wrote: > Hi > > The “typi

[time-nuts] Re: What's the best HP OCXO for frequency counter reference?

Hi The “typical” 10811 struggles when shut down for a while. Once the oven is turned off, the boards are just sitting there in whatever environment your lab provides. Do they soak up humidity or is it something else? We could (and have) debated that quite a bit. Regardless of what the issue

[time-nuts] Re: First PN measurement results at 1 Hz to 20 kHz from carrier

Hi > On Jun 27, 2022, at 1:43 AM, Erik Kaashoek via time-nuts > wrote: > > Magnus, Bob, > When the mixer is operating in the linear region for the DUT input (0dBm or > lower), would it be possible to use a calibrated noise sources to do an > extra verification of the noise level

[time-nuts] Re: First PN measurement results at 1 Hz to 20 kHz from carrier

Hi Ok, so mixer phase noise calibration: Set things up with “full blast” inputs to both sides of the mixer. Keep them at the same level through all tests. This might be +7 on both ports, it might be +13, it could be +20 dbm. ( yes, mixers *do* get fried this way ….). First cal step, you have

[time-nuts] Re: Knowing when the PPS signal is locked to the satellite.

Hi Keep in mind that if you run the PPS when unlocked, the uBlox does not “play nice” when it locks up. The PPS moves to where ever it needs to be quite abruptly. That may or may not create issues, depending on your application. Bob > On Jun 22, 2022, at 4:59 AM, Dave via time-nuts > wrote:

[time-nuts] Re: Fixing PN degradation via ADEV measurement

work on removing ground loops and adding low noise amplification. > Erik. > > On 21-6-2022 2:04, Bob kb8tq wrote: >> Hi >> >> Ok, single mixer phase noise basics: >> >> First thing is to womp the mixer up to the point it almost smokes. Putting >> +7

[time-nuts] Re: Fixing PN degradation via ADEV measurement

Hi Ok, single mixer phase noise basics: First thing is to womp the mixer up to the point it almost smokes. Putting +7 dbm into both ports on a “7 dbm” mixer is very normal in this case. Watching for the fact that the mixer likely is *not* a 50 ohm load is part of the process ( = pads might

[time-nuts] Re: Fixing PN degradation via ADEV measurement

option is to use a > second LO and a mixer and a slow (loop BW below 10 Hz)PLL to keep the mixer > in quadrature and feed the output of the mixer, after low pass filtering, > into a PC soundcard for FFT processing. > Erik. > > On 19-6-2022 22:45, Bob kb8tq via time-nu

[time-nuts] Re: Fixing PN degradation via ADEV measurement

Hi As HP found out back around 1973 or so, translating ADEV to phase noise is not possible. This is true, even if you have the ADEV numbers for a variety of Tau values as opposed to some sort of “average” kind of number. There are a number of things ( like spurs ) that can strongly influence a

[time-nuts] Re: Fixing PN degradation via ADEV measurement

Hi If the objective is “phase noise -130 dbc at a 10 KHz offset” and the signal is at 25 MHz, the resultant jitter ( in a 10 KHz bandwidth ) is likely in the < 500 fs range. The CNT-91 is only a 50 ps resolution device. Since it’s a counter, there is no practical way to vary the bandwidth.

[time-nuts] Re: Fixing PN degradation via ADEV measurement

Hi The CNT-91 has a very high noise floor if you are trying to “see” phase noise. It also does not give you much in the way of frequency offset information. A single mixer setup running into a sound card is a *much* better approach if you are looking for another opinion vs the FSQ8. I have used

[time-nuts] Re: Fixing PN degradation via ADEV measurement

Hi The “typical” approach to doing this is to multiply up to something around 100 MHz with a relatively narrowband PLL. You can get ( or build ) VCXO’s in this range with phase noise (at 10KHz offset) in the 160’s to (maybe) 170’s. This is much better performance than a 5 or 10 MHz reference can

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

> On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote: >> Hi >> >> Tear into some of your SC cut based OCXO’s. Take a look at the crystal >> package. For >> bonus points, open up the crystal package. If you have the gear to test it, >> take a look >>

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

gt; IR transmission of energy to the crystal also seems problematic considering > the IR transmission of quartz and the IR reflectivity of gold > contact plating. > > Is any of this an issue? > > - Louis > > On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts <

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

ystal also seems problematic considering > the IR transmission of quartz and the IR reflectivity of gold > contact plating. > > Is any of this an issue? > > - Louis > > On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < > time-nuts@lists.febo.com> wr

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts > wrote: > > On 6/10/22 1:57 PM, Dr. David Kirkby wrote: >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts >> wrote: >> >>On the subject of rapid warm up. I suppose if you had a need, one >>could >>dump as much power

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi Well …. folks have made AT based OCXO’s that heat up in “seconds” ( as in under a minute ). Back in the 1980’s they stabilized to < 1x10^-7 at least as fast as the then typical SC based OCXO’s did …. ( < 6 minutes ). Collins bought quite a few of them over the years. Bob > On Jun 10,

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi There happen to be *some* AT cut based OCXO’s that beat the typical SC cut on warmup … just saying …. :) Bob > On Jun 9, 2022, at 9:03 AM, Bruce Hunter via time-nuts > wrote: > > My only experience with SC-cut crystals is that time base oscillators in > later EIP/Phase-Matrix counters

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi Lower turning point has been done, both with AT’s (back in ~ the 1950’s) and with SC’s. Neither one showed any significant benefit. Taking a crystal down to sub 20K sort of temps does ramp up the Q. The gotcha is that the frequency vs temp curve is so steep that very minor temperature

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi I would be careful with that paper since part of what it says is not (in general) correct. Bob > On Jun 8, 2022, at 1:22 PM, Ross P via time-nuts > wrote: > > Hi,Thank you very much, this paper answered some questions. > >On Wednesday, June 8, 2022 at 12:38:04 PM PDT, Hans-Georg

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi Well ….. You can bash both AT’s and SC’s a *lot* harder than you might think. Both will suffer quite a bit in terms of ADEV when you do. Since the AT likely has a lower resistance (by quite a bit) than the SC, the loop current ( and thus the drive into the buffer) may not be as far

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

> > As far as I remember and know, you can achieve about the same > phase-noise properties as you hit about the same bandwidth from the Q, > and noise contribution is about the same. So, it boils down to do the > supporting amplifier well. > > Cheers, > Magnus &g

[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

Hi Simple answer is: no. More complete answer is: no There is a lot more to stability than just the crystal cut. Having this or that cut is in no way a guarantee that the result is “better” than some other cut. Indeed there are more exotic cuts than the SC that improve on this or that. There

[time-nuts] Re: Identifying GPSDO phase disturbers

Hi It’s a good bet that the TCXO has an AT cut crystal in it. That would give it a 1 to 2 ppb / G sensitivity for typical blanks mounted in a normal fashion. Quantifying the shock delivered by a “tap” on a part can be exciting. It can be done, but the gear to do it properly does cost more

[time-nuts] Re: Turning off display on HP 58503 A or B

Hi Both control loops in the 3801 OCXO’s are thermistor based. If the outside loop goes nuts, the device might survive. If the inside loop shorts out, the normal result is a melt down of the OCXO innards. Bob > On Jun 2, 2022, at 9:55 AM, K5jv via time-nuts > wrote: > > I was recently

[time-nuts] Re: Realtime comparing PPS of 3 GPS

Hi The variation you see is dependent on a number of things. One of them is space weather. If you do your run during a very active period ( typically peak sun spots) you may see some very dramatic swings on a single band device. Bob > On May 30, 2022, at 3:00 AM, Erik Kaashoek via time-nuts

[time-nuts] Re: Ublox M6T -M8T

Hi There are a number of threads on the uBlox receivers. Quick summary: All of the outputs from the typical examples are run with a “drop a pulse / add a pulse” approach to steer them to the correct frequency. If you are after a “clean” output for some sort of gear (like a synthesizer) … not

[time-nuts] Re: Optimizing GPSDO for phase stability

Hi What is the “customer” after? For a PPS, it could be the offset from UTC. This gets into GPS to UTC and then into GPS master to local GPS pulse. Bottom line usually is that the raw GPS pulse is the answer to “close to UTC”. Equally it could be a PPS used for metrology ( = ADEV

[time-nuts] Re: measuring tiny devices

.com/dishal-bandpass-filter-tuning-using-lasertrim-chip-caps> > > -John > > -----Original Message- > From: Bob kb8tq via time-nuts > Sent: Thursday, May 26, 2022 10:18 AM > To: Discussion of precise time and frequency measurement > > Cc: Bob kb8tq > Subject

[time-nuts] Re: measuring tiny devices

Hi The real answer to the problem is to dig into the bowels of 1940’s electronic craft. There are various methods for setting up an L/C filter. You short this / open that sweep to find a dip or a peak. You move it to the “right” place. Just what you do depends very much on the filter design.

[time-nuts] Re: Looking for an SMA GPS signal splitter

HI None of them mine: https://www.ebay.com/itm/144026433966 https://www.ebay.com/itm/201036132548 https://www.ebay.com/itm/112402977059 https://www.ebay.com/itm/233189112130

[time-nuts] Re: Does filtering a TCXO Vtune to reduce low tau ADEV with max 50% make sense?

Hi The typical answer to this issue is to first try to clean up the supply to the DAC. If that does not fix the issue, you likely need a better DAC. Unless the TCXO has a crazy large tune range, rational parts should be able to do the job. If the TCXO has a crazy large range then maybe a

[time-nuts] Re: Effect of temperature on cheap puck style GNSS antennas?

Hi > On May 12, 2022, at 3:21 AM, Lux, Jim wrote: > > On 5/11/22 11:50 PM, Matthias Welwarsky wrote: >> Dear list members, >> >> My DIY GPSDO has a rather well defined dependence to the environmental >> temperature, which correlates almost linearly with a frequency shift of the >> OCXO.

[time-nuts] Re: Can the ADEV of a GPSDO output ever be lower than the minimum of the ADEV of the internal oscilator and the ADEV of the GPS PPS?

HI > On May 10, 2022, at 5:42 AM, Attila Kinali wrote: > > On Tue, 10 May 2022 12:49:27 +0200 > Erik Kaashoek wrote: > >> Error bars like this? > > Exactly... > > And what you see is, that beyond ~300s the difference is not statistically > significant anymore and beyond 700s the curves are

[time-nuts] Re: OSA-5400 power transistor

Hi With 24V in, 450 ma is 10.8W. That’s a pretty hearty number for warming up an OCXO. That power would not be going through the 18V regulator for a couple of reasons. Once warmed up, 170 ma at 24V is 4.08W. That’s more than a functioning OCXO should pull at typical lab bench temperatures. 60

[time-nuts] Re: Simple simulation model for an OCXO?

16:23:27 -0500 > Bob kb8tq wrote: > >> The gotcha is that there are a number of very normal OCXO “behaviors” that >> are not >> covered by any of the standard statistical models. > > Could you elaborate a bit on what these "normal behaviours" are? > &g

[time-nuts] Re: Simple simulation model for an OCXO?

Hi The gotcha is that there are a number of very normal OCXO “behaviors” that are not covered by any of the standard statistical models. Coping with these issue is at least as important at working with the stuff that is coved by any of the standard statistical models …. Bob > On May 3,

[time-nuts] Re: Simple simulation model for an OCXO?

022 at 10:01 PM Bob kb8tq wrote: >> By far the best approach is to use actual data. Grab a pair of OCXO’s and >> compare them. A single mixer setup is one easy ( = cheap ) way to do it. You >> will get the sum of the two devices, but for simulation purposes, it will be >>

[time-nuts] Re: Simple simulation model for an OCXO?

Hi By far the best approach is to use actual data. Grab a pair of OCXO’s and compare them. A single mixer setup is one easy ( = cheap ) way to do it. You will get the sum of the two devices, but for simulation purposes, it will be *much* closer to reality than anything you can brew up with a

[time-nuts] Re: Can the ADEV of a GPSDO output ever be lower than the minimum of the ADEV of the internal oscilator and the ADEV of the GPS PPS?

Hi If you have a FS740 and measure it’s performance …. you likely will take anything the manual says a lot less seriously ….. Their ADEV performance in the real world is a bit underwhelming. Bob > On May 2, 2022, at 1:42 AM, Markus Kleinhenz via time-nuts > wrote: > > Hi Erik, > > I just

[time-nuts] Re: What time difference to expect from two clocks using internal GPS receivers?

Hi If you are looking at time ( = the absolute offset from GPS’s version of UTC) then there are a number of issues. The antenna you use will have a delay and it may well vary more than a bit. The cable to the antenna is in the same category. If both your modules run off a power splitter

[time-nuts] Re: GPS Control Loop

Hi > On Apr 27, 2022, at 1:09 PM, ASSI wrote: > > On Dienstag, 26. April 2022 23:20:34 CEST Lux, Jim wrote: >> That's the MCXO - uses third harmonic and fundamental to measure the >> temperature. Q-Tech sells them. Or, more properly, has them in their >> catalog and may be happy to quote a

[time-nuts] Re: GPS antenna locations

nd side mounting it on > the tower, then doing a comparison of the signal strength vs az/el plot > against this roof mounted one. It is an extra expense I will have to find a > way to budget for, but certainly has educational value if nothing else. > > Paul > > >

[time-nuts] Re: GPS antenna locations

Hi Not knowing everything about the local environment there’s not much way to guess exactly what this or that location will do. The biggest thing I see on your plot is something due south of the current antenna location. In a “typical” setup, anything within 20 degrees of the horizon gets

[time-nuts] Re: Question about GPS 1PPS ADEV

Hi Any time you look inside a control loop, there will be bumps and the like that are a function of the control loop plus the dynamics of the device being controlled plus the environment. If you have a straight line … something is wrong. Bob > On Apr 16, 2022, at 1:20 PM, Matthias Welwarsky

[time-nuts] Re: Question about GPS 1PPS ADEV

Hi > On Apr 16, 2022, at 11:55 AM, John Ackermann N8UR wrote: > > > > On 4/16/22 09:52, Matthias Welwarsky wrote: >> Dear list members, >> in 2020 John Ackermann published an evaluative survey of current day GPS and >> GNSS receivers (URL below). I have a question about figure 26, which

[time-nuts] Re: General discussion of PID algorithms applied to GPSDO control loops (continued 1)

Hi Even if you *do* have a number for your OCXO EFC, what is that number? The nominal sensitivity is fine. The next layer is the ratio of maximum slope to minimum slope. This is a very different thing than the “linearity” that is normally specified. Even the linearity is something you need to

[time-nuts] Re: General discussion of PID algorithms applied to GPSDO control loops (continued 1)

Hi > On Apr 15, 2022, at 8:36 AM, André Balsa wrote: > > Hi Bob, thank you for your comments, very helpful. > > On Fri, Apr 15, 2022 at 2:06 PM Bob kb8tq wrote: > >> Hi >> >>> For example, the STM32 GPSDO with >>> its very crude FLL algori

[time-nuts] Re: General discussion of PID algorithms applied to GPSDO control loops (continued 1)

Hi > On Apr 14, 2022, at 12:00 PM, André Balsa wrote: > > 10. Again referring to our ideal PID controller, our control variable u(t) > in the case of most low-cost GPSDOs is the control voltage that we can > apply to the OCXO to vary its frequency. For Lars' DIY GPSDO and for the > STM32 GPSDO

[time-nuts] Re: +1/f of transistors

Hi As noted in many posts, 1/F noise is dependent on a number of operating parameters. The first thing to do would be to understand your use case. Testing under one set of conditions may not be useful for use in other conditions. Bob > On Apr 10, 2022, at 5:50 AM, Leon Pavlovic wrote: > >

[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

Hi Crystal filtering for far removed phase noise does work. It’s far from a “perfect” solution. The crystal it’s self contributes noise and it does AM to PM conversion. You pretty much always get a “noise hump” as a result. Like any filter, a single crystal filter has an attenuation vs

[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

Hi Since this is Time Nuts … crazy isn’t always ruled out :) > ………. > “TSP #162 Tutorial on Theory, Characterization & Measurement > Techniques of Phase Noise" > > https://www.youtube.com/watch?v=SOHjFtw0sgo > > each 5db of improvement requires an order of magnitude increase in >

[time-nuts] Re: GPScon peogram

Hi Since some of these programs are indeed a bit tough to find (and when found run on this or that machine), It might be useful to know what the target device is. There are a lot of programs out there and a good deal of overlap in terms of what they support. Bob > On Apr 5, 2022, at 7:33 PM,

[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

01d84732$bcc47c40$364d74c0$@t-online.de> >> Content-Type: text/plain; charset="utf-8" >> >> Hi, >> >> This is nearly "off-the shelf" model: >> https://www.axtal.com/cms/docs/doc100916.pdf >> The ULN version does meet the -1

[time-nuts] Re: 32.768Khz Crystal Trimming

Hi The cap ratio very much depends on how the internals of the chip got done. Since you have zero info on that, it’s best to stick with the ratios and approximate values shown in the app notes. The most common way to get a fine grain tune is to put something large in series with the crystal

[time-nuts] Re: Commercial solution - 122.88 Mhz low noise source

any design work or > project construction time. > > 73/jeff/ac0c > alpha-charlie-zero-charlie > www.ac0c.com > > > On 4/4/22 7:36 AM, Bob kb8tq wrote: >> Hi >> >> For a variety of reasons, you will have a loop bandwidth in the > 10 Hz >> to &l

[time-nuts] Re: Commercial solution - 122.88 Mhz low noise source

;frequency control" without degrading the noise > characteristics of the VCXO. > > 73/jeff/ac0c > alpha-charlie-zero-charlie > www.ac0c.com > > > On 4/3/22 7:38 PM, Lux, Jim wrote: >> On 4/3/22 5:09 PM, Bob kb8tq wrote: >>> Hi >>> &

[time-nuts] Re: Commercial solution - 122.88 Mhz low noise source

Hi Does the Abricon have an EFC input? If so, rigging up a PLL to lock 122.88 to 10 MHz is probably the best option. Bob > On Apr 3, 2022, at 7:57 PM, Jeff Blaine wrote: > > I've got a couple of Red Pitaya 122-16 SDR and want to discipline them to an > external low noise GPSDO source.

[time-nuts] Re: TIC reference clock in 3-cornered hat

Hi A lot depends on just what is being measured. If you are looking at three PPS signals, you *might* be running on the internal reference for a second. If you are comparing 10 MHz signals, the max time is 100 ns. Getting (say) 1 ps accuracy in the first means 1x10^-12 / 1 = 1 ppt on your

[time-nuts] Re: Low Phase Noise 10 MHz bench signal source sought

Hi These days a PLL is going to either be analog or digital. If it’s analog, you get into size constraints related to capacitors as you go to lower crossover frequencies. With digital, you get into all of the noise issues that any digital circuit will have. (Yes, they can be addressed but it’s

[time-nuts] Re: Can one use a two channel TC with an internal reference to measure two independent oscillators to establish the quality of the internal reference?

Hi Usually the best / quick / easy way to evaluate something like a two channel counter is do it with a pair of signals that are independent from each other, but very close to the same frequency. Rb’s are often used, but the technique is not specific to them. You feed a PPS ( or whatever ) from

[time-nuts] Re: Low Phase Noise70 10 MHz bench signal source sought

Hi Rb and low phase noise ( at least far removed ) are sort of mutually exclusive specs. You need to pick one … Assuming the decision is to go for the -170 dbc/Hz spec, Congratulations you are buying on OCXO. Not quite clear which OCXO, but it’s pretty likely to be an OCXO. (Yes, there are

[time-nuts] Re: 32.768Khz Crystal Trimming

Hi The typical 32 KHz crystal has a parabolic tempco. It peaks at kinda sorta room temperature. This makes it work pretty well on a normal wrist. As you get away from ~ 25C, the frequency drops. Since it’s a parabola, the further away from room you get the faster it drops. Something in the

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