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
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
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
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
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
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
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
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
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
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
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
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
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
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”
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
If you don't like how the Tbolt adjusts the oscillator on your Tbolt... do it
yourself. You can set up the Tbolt for manual DAC control and implement your
own control loop. Warren Sarkison and I implemented a alternate control PID
for the Tbolt DAC. Yep, it's in Lady Heather. It's been
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.
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
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
Kehren via time-nuts" <time-nuts@febo.com>
To: <time-nuts@febo.com>
Sent: Thursday, September 01, 2016 9:54 AM
Subject: [time-nuts] Tbolt issues
> We have been following the Tbolt power discussions but what I am missing is
> the main problem with Tbolts. All the power work wi
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
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.
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
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
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*
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
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
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
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
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
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,
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
TBolts that
I see. Something is wrong.
>
> /tvb
>
> - Original Message -
> From: "Bert Kehren via time-nuts" <time-nuts@febo.com>
> To: <time-nuts@febo.com>
> Sent: Thursday, September 01, 2016 9:54 AM
> Subject: [time-nuts] Tbolt issues
al noise and wander,
> down at the 1e-11 level. How does this compare with yours?
>
> Your claim of 1e-10 is order(s) of magnitude worse than the TBolts that I
> see. Something is wrong.
>
> /tvb
>
> - Original Message -
> From: "Bert Kehren via
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
We have been following the Tbolt power discussions but what I am missing is
the main problem with Tbolts. All the power work will not improve the
frequency performance of the unit because the frequency is constantly changed
to correct time. Tbolt is an excellent time device but not good for
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