Re: [time-nuts] Tbolt issues

Know all that that is why we decided not to do it. Not knowing all the ins and outs and limits of the Tbolts that is why I asked the question to begin with Bert Kehren Sent from Samsung tabletCharles Steinmetz wrote:Bert wrote: > On our to do list was temperature

Re: [time-nuts] Tbolt issues

Bert wrote: On our to do list was temperature control and clean up loop. In order to do an analog clean up we need short interval changes and that is why I went on the list since we have not been able to do it and looking at past posting have not found data that will get us there. To do

Re: [time-nuts] Tbolt issues

Yes Charles I was not part of or following the original Tbolt discussions. My setup at the time was Loran C with Austron 2110, backed up with Cs and 60 Khz using a Tracor 599H. My work was focused on FRK FRS Rb’s using Shera with very good results. At the same time Juerg was using a

Re: [time-nuts] Tbolt issues

Warren wrote: The most important thing to get good Tbolt frequency performance is the antenna, with good sky view and correct location setting. Agreed. Nothing will go right if the antenna, sky view, and surveyed location are not as good as you can get them. The Tbolts damping setting is

Re: [time-nuts] Tbolt issues

Bert wrote: Looks like we are not the only ones trying to improve frequency performance and hopefully some one will share settings. You are coming very late to the Tbolt party. There was a veritable blizzard of posts about optimizing Tbolt performance, which began maybe 10 or 11 years ago

Re: [time-nuts] Tbolt issues

Bob wrote: The one thing that autotune seems to do well is to come up with the actual sensitivity of the OCXO you have. It depends on a few things to do this so it might go wrong. I’ve never seen it come up with the wrong number. It then appears to drop in a gain and damping that make more

Re: [time-nuts] Tbolt issues

Bert a) 1e-10 freq error, Sounds to me like you have a typical TBolt with near factory default setting. The most important thing to get good Tbolt frequency performance is the antenna, with good sky view and correct location setting. After that there are some 'basic' Tbolt setting and things

Re: [time-nuts] Tbolt issues

Charles would you mind sharing 1 second frequency data that you get out of the tbolt to get an idea what is possible. Looks like we are not the only ones trying to improve frequency performance and hopefully some one will share settings. Bert Kehren In a message dated 9/10/2016 6:42:17

Re: [time-nuts] Tbolt issues

Bert wrote: would you please share your settings, this is exactly what we are looking for. We are doing it by trial and error but your expertise will help greatly. Well, I spent the holiday weekend looking for the "safe place" where I recorded my final Tbolt tuning parameters -- without

Re: [time-nuts] Tbolt issues

Hi > On Sep 10, 2016, at 6:40 AM, Charles Steinmetz wrote: > > Bert wrote: > >> would you please share your settings, this is exactly what we are looking >> for. We are doing it by trial and error but your expertise will help greatly. > > Well, I spent the holiday

Re: [time-nuts] Tbolt issues

Hi The problem is that ADEV is not really the best tool for measuring / modeling narrow band noise. There are other measures that are better. None of them really give you a direct connection to a band limited noise process. Without a model for the process, coming up with a max limit is just

Re: [time-nuts] Tbolt issues

You are absolute right in that it is a that depends sort of things. Fast temperature changes might really be something that upsets a GPSDO especially if the time constant is long. By taking temperature data and multiply with your oscillators temperature coefficient you can do ADEV for the

Re: [time-nuts] Tbolt issues

Hi Since the measurement in the frequency domain is a "peak" measure, you need to convert both to frequency error and to an absolute max. If you *do* care about the one second per day (or 10 days) as some do, that is a different factor than one second out of two minutes. Since the noise is

Re: [time-nuts] Tbolt issues

I might be completely wrong with my ”quick rule of thumb” (frequency accuracy: 10x the worst ADEV at all Taus longer than the gate time). but my assumptions are these: 1. You have a GPSDO. (A free running oscillator as a rubidium or OCXO will not work if that is what you call a ”normal”

Re: [time-nuts] Tbolt issues

Hi Just to be a bit more clear: This is *not* something unique to the Tbolt. It shows up on all GPSDO's. There have been a lot of posts with data plots showing this on lots of GPSDO's. The issue is more basic than a goof in a control loop setting. To some extent it is a problem on all

Re: [time-nuts] Tbolt issues

Charles, would you please share your settings, this is exactly what we are looking for. We are doing it by trial and error but your expertise will help greatly. English not being my native language linguistics are some time a problem Thanks Bert In a message dated 9/1/2016 6:26:32 P.M.

Re: [time-nuts] Tbolt issues

Hi The GPSDO might have an ADEV of 1 ppt at 1 sec and that rises to 30 ppt at 100 sec. It also might not, but let's use those numbers. ADEV is a standard deviation. You can get an idea of the magnitude of the change reading to reading from it. It does not give you a sign for that change. In

Re: [time-nuts] Tbolt issues

Hi The gotcha in your approach is that you are using more than one sample out of the system to get frequency. Thus you are measuring over a time period. To get instantaneous frequency you need to base it on a single sample. There are some other restrictions (infinite bandwidth being the big

Re: [time-nuts] Tbolt issues

Hello Tom, What are the conditions for your charts? Are the Tbolts in locked condition or holdover? If locked what settings do you have for time constant and damping? Is it any other setting that is important? For the frequency chart I see excursions up to +-3E-11 so not so far from the

Re: [time-nuts] Tbolt issues

Hello Bert, For me your findings look very much the same as this: http://www.leapsecond.com/pages/tbolt-8d/ At least for me I should say the (absolute) frequency accuracy for this Tbolt is not better than +-1E10 with 1 or 10 seconds gate times on a counter. Maybe I am totally wrong as both Tom

Re: [time-nuts] Tbolt issues

Jim wrote: Instantaneous frequency does have a theoretical meaning, even if not measureable.. If I'm processing a linear frequency chirp, I can say that the frequency at time t is some (f0 + t*slope). the frequency at time t+epsilon is different, as is the frequency at time t-epsilon.

Re: [time-nuts] Tbolt issues

On Fri, Sep 2, 2016 at 12:51 AM, Charles Steinmetz wrote: > Now shorten the observation time to 20nS. We see 1/5 of a complete cycle > (72 degrees, 0.4 pi radians) of the wave. No matter which particular 72 > degrees we see, we simply don't have enough information to

Re: [time-nuts] Tbolt issues

The problem is that "frequency" has more than one meaning. The main dictionary definitions have to do with the frequency of occurrence of some items in a category with respect to a larger set, or the frequency of occurrence of some repeating event per unit of time. But we also use mathematical

Re: [time-nuts] Tbolt issues

On 9/1/16 5:51 PM, Charles Steinmetz wrote: Nick wrote: On a theoretical basis, can one speak of the limit of the frequency observed as tau approaches zero? Might that in some way be the "instantaneous frequency" which people often think of? That is (or is "something like") what it *would*

Re: [time-nuts] Tbolt issues

Nick wrote: On a theoretical basis, can one speak of the limit of the frequency observed as tau approaches zero? Might that in some way be the "instantaneous frequency" which people often think of? That is (or is "something like") what it *would* be, but a little thought experiment will

Re: [time-nuts] Tbolt issues

Hi Unfortunately if you read a typical text on FM modulation, "instantaneous frequency" comes up pretty fast. In that context it has a valid meaning. Once out of context, it gets you in trouble. That point is never made when the term is introduced. Bob > On Sep 1, 2016, at 8:51 PM, Charles

Re: [time-nuts] Tbolt issues

Bert wrote: maybe some one smarter than us can working with the parameters that Tbolt makes available better performance can be achieved I am quite sure of that the frequency is being changed to compensate for time Yes, the PPS is steered by making slight adjustments to the OCXO

Re: [time-nuts] Tbolt issues

Hi Frequency is a "change over time". If delta time is zero it is undefined. As you observe it in shorter time periods, the accuracy / stability gets worse. Since the error bars expand there isn't much of a limit as you go shorter. They are not quite the same thing, but they are related. Bob

Re: [time-nuts] Tbolt issues

Tom wrote: No, again it sounds like you have a bad TBolt. Or something is wrong (antenna? reception? time constant? environment? China resoldered parts?). I appreciate that Juerg did lots of testing -- do you happen to have his ADEV plot? Your claim of 1e-10 is order(s) of magnitude worse

Re: [time-nuts] Tbolt issues

Hi The problem with absolute frequency is the one they ran into in the 60’s (and before): There is no really good way to measure it. You certainly can take data. The data can have lots of resolution. That part has always been fairly easy. The problem is that the more carefully you look,

Re: [time-nuts] Tbolt issues

maybe some one smarter than us can working with the parameters that Tbolt makes available better performance can be achieved but it is a fact that the frequency is being changed to compensate for time and Tom's frequency data matches our's and we do not care about ADEV, we care about the

Re: [time-nuts] Tbolt issues

For us it is absolute Frequency, to me it is a measure of true performance. In a message dated 9/1/2016 4:52:35 P.M. Eastern Daylight Time, kb...@n1k.org writes: Hi I think one issue here is that ADEV is being used by one “lab" and absolute frequency is being used by the other. They

Re: [time-nuts] Tbolt issues

Hi I think one issue here is that ADEV is being used by one “lab" and absolute frequency is being used by the other. They very much are *not* the same thing. There isn’t even a really simple way to convert one to the other. There will always be a big delta between those two measures. For

Re: [time-nuts] Tbolt issues

On Thu, September 1, 2016 11:54 am, Bert Kehren via time-nuts wrote: > All the power work will not improve the frequency performance > of the unit because the frequency is constantly changed > to correct time. Can't you control that to a large extent with the damping and time constant