Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Backing up a bit: If you are going to measure something like a crystal oscillator against a PPS, you need to be careful of phase slip. The oscillator may be off frequency by many ns/s. Working out what happens as it crosses a 100 ns boundary is not as easy as one might think. In addition, c

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi, If you have a GPSDO, then PPS as re-generated from the locked oscillator is naturally less noisy than straight from the GPS. Using a PICDIV helps you to use another reference instead, and the TADD-2 is a useful option to consider. I have my TADD-2:s modified such that one of the outputs is th

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

YES, please.  tkami...@yahoo.com. So far, I've taken HP105B and did adev frequency reading based, T.I. based adev, and while at it, I am doing PRS-10 T.I. based. I have a question.  My 1 second reference for channel A is coming from GPS based 1 second.  I understand it's only 10E-8 precision on s

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi, On 2020-02-29 23:10, Taka Kamiya via time-nuts wrote: > One question for Magnus. > > Ch A start - pps (standard)Ch B stop - DUT > On item 4, you said "frequency of the signal on time B".  That much is > obvious.  But then you said: "give it the time-base of the period on the > A-channel".  W

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

One question for Magnus. Ch A start - pps (standard)Ch B stop - DUT On item 4, you said "frequency of the signal on time B".  That much is obvious.  But then you said: "give it the time-base of the period on the A-channel".  Will you explain this? Say I give 1 Hz, period is 1s.  Say I give 10Hz,

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

SDRs (Software Defined Radio) decimate / downsample. Look at SDR documentation. Google turns up: https://dspguru.com/dsp/faqs/multirate/decimation/ Robert On 02/21/2020 03:09 PM, Gary E. Miller via time-nuts wrote: Yo Magnus! On Fri, 21 Feb 2020 20:33:46 +0100 Magnus Danielson via time-nuts

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Taka, On 2020-02-22 16:08, Taka Kamiya via time-nuts wrote: > As I understand, 3 cornered hat is nothing more than system of equations > where you have 3 variables and 3 equations, that allows for solving for each.  > I'm going to hold off on that one.  I forgot about thermal and equipment's

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

As I understand, 3 cornered hat is nothing more than system of equations where you have 3 variables and 3 equations, that allows for solving for each.  I'm going to hold off on that one.  I forgot about thermal and equipment's internal noise.  It all makes sense.  I hope to be doing some measuri

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Taka, On 2020-02-22 04:55, Taka Kamiya via time-nuts wrote: > It's not like drinking from a fire hydrant.  It's like drowning in hoover > dam, get sucked into an inlet, pulverized by turbine blade, and getting spit > out into a stream.  Hmm, not exactly what I had hoped for as your experienc

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

It's not like drinking from a fire hydrant.  It's like drowning in hoover dam, get sucked into an inlet, pulverized by turbine blade, and getting spit out into a stream.  One question :  You said this: "The resolution of your counter tells you about where your 1/tau curve will cut tau = 1 s,

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Taka, On 2020-02-21 23:26, Taka Kamiya via time-nuts wrote: > I'm sorry, I messed up.  I jumped on more advance topic than I intended.  I'm > sure there were answers in the replies but they must have gone way over my > head because some of original questions still remain.  I bulletized (is th

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

HI > On Feb 21, 2020, at 5:26 PM, Taka Kamiya via time-nuts > wrote: > > I'm sorry, I messed up. I jumped on more advance topic than I intended. I'm > sure there were answers in the replies but they must have gone way over my > head because some of original questions still remain. I bullet

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

I'm sorry, I messed up.  I jumped on more advance topic than I intended.  I'm sure there were answers in the replies but they must have gone way over my head because some of original questions still remain.  I bulletized (is that a word?) the original question with my NEW understanding.  Would s

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi, For white phase modulation noise and flicker phase modulation noise, ADEV depends on filter bandwidth, but not for the others, according to theory. This is naturally an approximation, but it works out like that pretty much in real life too, so it works as an approximation... until you try to d

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi With phase data on ADEV, you are pretty much always *under-sampling* the data. As you go to longer tau’s you do not do any bandwidth fiddling. The sample rate drops and drops, but the bandwidth stays the same. Bob > On Feb 21, 2020, at 4:04 PM, Chris Caudle via time-nuts > wrote: > > On F

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi, You want to be sure that you do not reduce the bandwidth of the final product too narrow, because most will assume it is the full Nyquist bandwidth. Filter to avoid antialiasing is fine and needed, but beyond that, do not over-filter. Cheers, Magnus On 2020-02-21 21:09, Gary E. Miller via t

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Yo Magnus! On Fri, 21 Feb 2020 20:33:46 +0100 Magnus Danielson via time-nuts wrote: > As one decimate data, one needs to be very very careful with > bandwidth. It would make biases in values which would over-state > stability. Yes, we have seen it happen. Even big names has come clean > and conf

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

On Fri, February 21, 2020 2:27 pm, Bob kb8tq via time-nuts wrote: > Which is why downsample is probably a better term since it does not > involve fiddling bandwidth. I would expect that you would still have to meet Shannon-Nyquist criteria and low-pass filter before reducing the sampling rate. I d

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Which is why downsample is probably a better term since it does not involve fiddling bandwidth. Decimate can mean “just throw it out” so you do see it used in some papers that way. Bob > On Feb 21, 2020, at 2:33 PM, Magnus Danielson via time-nuts > wrote: > > Hi, > > As one decimate dat

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Bert, I missed it because I do not have one or worked with one, which is not to say it is bad or anything, I just took the examples I recall because it is familiar to me. There is more of these for sure. I hope it was good enough to illustrate the points with some real-life examples. Cheers, Magn

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi, As one decimate data, one needs to be very very careful with bandwidth. It would make biases in values which would over-state stability. Yes, we have seen it happen. Even big names has come clean and confessed doing it wrong when they decimated the data. Cheers, Magnus On 2020-02-21 17:12, B

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi The primer talks a lot about “averaging” of the samples. If you dig deep into the various papers on doing AVAR for frequency / time standards … you want to decimate / downsample the data rather than average. There are a *lot* of papers that make this distinction less than totally clear.

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Here is a good article for Allan deviation that you can file with other reference material. It is well written and somewhat high level. https://www.phidgets.com/docs/Allan_Deviation_Primer Chris On 02/20/20 21:45:58, Taka Kamiya via tim

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

You missed my favorite  HP5345A  only direct 500 MHz and internal 500 MHz, only recently replaced it with 53132A still use it for 40 GHz work Bert Kehren In a message dated 2/21/2020 7:27:32 AM Eastern Standard Time, mag...@rubidium.se writes: Hi Taka, On 2020-02-21 04:45, Taka Kamiya via ti

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Taka, On 2020-02-21 04:45, Taka Kamiya via time-nuts wrote: > I was in electronics in big ways in 70s.  Then had a long break and came back > to it in last few years.  Back then, if I wanted 1s resolution, the gate time > had to be 1s.  So measuring ns and ps was pretty much impossible.  As I

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

I was in electronics in big ways in 70s.  Then had a long break and came back to it in last few years.  Back then, if I wanted 1s resolution, the gate time had to be 1s.  So measuring ns and ps was pretty much impossible.  As I understand it, HP53132A (my main counter) takes thousands of samples

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi Taka, On 2020-02-20 19:40, Taka Kamiya via time-nuts wrote: > I have a question concerning frequency standard and their Allen deviation.  > (to measure Allen Dev in frequency mode using TimeLab) > > It is commonly said that for shorter tau measurement, I'd need OCXO because > it's short tau j

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

We use Dual Mixer 10 Hz offst but also Adret and Tracor 10 000 X multipliers along with HP53132ABert Kehren In a message dated 2/20/2020 3:15:17 PM Eastern Standard Time, kb...@n1k.org writes: Hi For most good standards, all a frequency counter is measuring at a 1 second gate is the floor o

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

Hi For most good standards, all a frequency counter is measuring at a 1 second gate is the floor of the counter: A typical counter might have a 100 ps rms sort of “gate error” at 1 second. That means that the best it actually can do is 100 ppt = 1x10^-10. A good oscillator will have an RMS cou

Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

This is exactly why we have disciplined oscillators: the short term stability of an OCXO steered with the long term stable accuracy of GNSS, Cs beam/fountain or H maser. On Thu, Feb 20, 2020 at 7:41 PM Taka Kamiya via time-nuts wrote: > > I have a question concerning frequency standard and their

[time-nuts] Frequency standards for different tau in Allen Dev measurement

I have a question concerning frequency standard and their Allen deviation.  (to measure Allen Dev in frequency mode using TimeLab) It is commonly said that for shorter tau measurement, I'd need OCXO because it's short tau jitter is superior to just about anything else.  Also, it is said that fo