Hi Warren,
Something to be careful about when doing what you suggest is that the two
Tbolts will not switch birds at the same time, so need to not use that
part of the data if you want to remove the effect of the GPS. Treat that
part like outliners.
Right that is a problem when looking at
Tom
Thanks for the Tbolt vs. H-maser data log,
That's great data showing how good GPS can be out to 200,000 sec with SA
off.
Your data showing a little under 5e-14 at 1 day, makes a very good reference
point to remember.
Any guess when your plot would flattens out or turn around?
It is also
Azelio,
Oh, yes, you're right. 100pS is the noise. Very interesting in this case:
how this high resolution is obtained (excluding averaging, the real
hardware
resolution)? Analog interpolators? Wave union TDC? Vernier delay lines? I
haven't found any reference in the internet...
There is no
Oh my, you're absolutely right... I've totally missed out those few lines!
Now I understand. I apologize and go immediately to search for a Tbolt. A
similar design is the ConnorWinfield/NavSync FTS125 but instead of
disciplining an OCXO they use a 20MHz fixed OCXO (without EFC) to drive the
GPS
Tbolt Nuts
Something I see on Ed's SAS antenna plot that my be of interest to others.
Antenna vew looks pretty good for the most part (besides the Noth blockage)
but there are several small 5 to 10 db nulls in the middle of otherwise
strong signals, especially facing south.
One thing that can
Your work is very interesting, now I wonder what is the Tbolt
single-shot resolution? Does the Tbolt use the analog interpolator
method? I don't have the Tbolt, I have an HP58503A at work as the only
reference.
On 10/13/11, WarrenS warrensjmail-...@yahoo.com wrote:
John wrote:
I'm curious where
I know very little about the HP58503A. Any chance it is using the old 6
channel Oncore GPS engine?
If it is like the Oncore I tested long ago, that noise was about a decade or
so higher than the Tbolt's phase noise.
Not sure what you can call single-shot resolution. The data is reported with
The HP58503A has the Oncore 8-channel GPS receiver. The single-shot
resolution capability is the ability to resolve the time interval
without any averaging. For example, the Fluke/Pendulum PM6681/CNT81
has a 50pS resolution, the HP5370 has 20pS, the Racal Instruments 2351
VXI TIC has 8pS single
is \
***
[time-nuts] Measuring ADEV using TBolt-Tic tester
Azelio Boriani azelio.boriani at screen.it
Thu Oct 13 10:21:40 UTC 2011
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The noise of the Tbolt's freq (PPT) output data measured about ten times
lower than it's phase output data at 1 sec.
How it does it is anyone guess, but looks to be some sort of high speed
averaging going on, taken over a one second time interval.
ws
The short-term frequency values could be
Using the 1 sec ADEV noise floor from the plot at
http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gifthis shows the RMS sum of the short term GPS signal's noise Plus the Tboltengine, plus the Osc, for the achievable resolution at 1 second.The one shot,
I'll try again.
My last post was completely garbled somewhere along the line.
Using the 1 sec ADEV noise floor from the plot at
http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gif
This shows the RMS sum of the short term GPS signal's noise Plus the Tbolt
Hi Tom,
The noise of the Tbolt's freq (PPT) output data measured about ten times
lower than it's phase output data at 1 sec.
How it does it is anyone guess, but looks to be some sort of high speed
averaging going on, taken over a one second time interval.
ws
The short-term frequency
Thanks Tom very interesting.
I like your guess on how they get such a low noise for the PPT data.
I would like to know why they would go to the trouble, because I don't see
anywhere that information is used except for the PPT output.
Alos the Tbolt's PPT freq data, long term is usually offset
Good ideas, That's more to put on my to do list, But not near the top.
I've got two external Tbolts (one is a loaner) plus an internal one.
Right now I'm limited because of some long term testing I doing.
Something to be careful about when doing what you suggest is that the two
Tbolts will not
You missed something somewhere
The Tbolt's RMS noise is 100 ps for the phase and 10 ps noise on the PPT
using unfiltered one second data.
These include the RMS sum of several noise sources.
The resolution is sub ps.
The noise is much greater than the resolution so averageing works fine
ws
Oh, yes, you're right. 100pS is the noise. Very interesting in this case:
how this high resolution is obtained (excluding averaging, the real hardware
resolution)? Analog interpolators? Wave union TDC? Vernier delay lines? I
haven't found any reference in the internet...
On Thu, Oct 13, 2011 at
John wrote:
I'm curious where you got the noise data for the TBolt GPS engine
Besides the measured ADEV plot I posted at
http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gif
Attached is another way I've measured Phase noise of the Tbolt, to optimizing
On 07/10/11 19:00, WarrenS wrote:
Use the (J J) command to rezero the Phase plot (plus the cable delay if
desired)
and then read or adjust the Osc freq on the ppt plot.
With LadyHeather's filter off (F D 0) useful resolution is about 1e-10
in one second,
With the filter set to 10 sec (F D 10)
I know that few of the GPS constellation satellites carry a Cs clock instead
of the Rb one: is it possible to take advantage from this? I think not
because Cs and Rb satellites are equally well steered but using the masking
options of GPS receivers maybe that Cs clocks can help.
On Fri, Oct 7,
Very Important note, The above is NOT available directly from
LadyHeather's
ADEV plots (at least not yet - Mark is a revision coming?),
What one needs to do is to log the Tbolt's Freq and Phase data at the 1
sec
rate and then use that data with an external ADEV program such as Ulrich's
Magnus
I probable was not very clear in my posting. (what else is new?)
There where TWO completely different subjects, goals and techniques in the
same Posting.
#1 was how to Log data for valid ADEV plots. That takes setting the filter
OFF for the reasons you state.
The ADEV tau axes provides
You would first have to answer which are better to use for short term, Cs or
Rb?
(the answer is: a good OCXO)
My guess is it does not mater, all are so much better than what is received
by a Tbolt.
And for long term where a Cs wins, they are disiplined/corrected in some
way so it don't mater.
On Oct 7, 2011, at 3:32 PM, John Miles jmi...@pop.net wrote:
Intuitively, I don't believe a GPSDO can outperform an HP 5071A-era clock
over periods greater than a few hours. But it may be reasonable to
benchmark 5061A-class standards with a good GPSDO setup. We really need
some more data
Hi,
As for the CS vs RB on orbit, the Elmer Perkins RBs on IIR are better out
to a few days than CS on the older satellites. Anybody knows which clocks
are in the new IIF-satellite on orbit? Any performance data published?
--
Björn
You would first have to answer which are better to use for
John
It would be great to have a direct Tbolt driver on TimeLab.
Right now it is so much trouble and time to use it, it takes away of the
great real time capabilities of TimeLab.
According to Tom his really good Cs has an Flicker noise floor of almost 10
days using 4 ns rms for phase noise.
On 07/10/11 20:59, Azelio Boriani wrote:
I know that few of the GPS constellation satellites carry a Cs clock instead
of the Rb one: is it possible to take advantage from this? I think not
because Cs and Rb satellites are equally well steered but using the masking
options of GPS receivers maybe
John
What was the RMS and PP phase noise for your 8e-14 test?
Something to keep in mind is that although the Z3801 has a better Osc than
the typical Tbolt.
Long term, really low noise is all about the quality of the GPS signal and
engine.
The Z3801's GPS engine is far inferior and not even
Long term, really low noise is all about the quality of the GPS signal and
engine.
And the antenna, and the multi-path, and ionosphere, etc. ...
With a Z3801A or TBolt (or any cheap single channel GPS) receiver
you should expect maybe a 5 to 10 to 15 ns variation over a 12 or 24
hour period.
In that test I was just capturing the ADEV table from the TSC-5120 so don't
have raw phase data.
I'm curious where you got the noise data for the TBolt gps engine -- that's far
better than I've seen quoted before. The Trimble data sheet that I found specs
the system PPS accuracy at 20
Hi Tom and Warren,
With a Z3801A or TBolt (or any cheap single channel GPS) receiver
you should expect maybe a 5 to 10 to 15 ns variation over a 12 or 24
hour period. You should be able to see this with a 5065A or a good
Cs reference.
Hope to get a working 5065A in a month or two... ;-)
The noise data is my measured values which I do several different ways. Some
of which are:
The GPS engine value was calculated from measuring the UNFILTERED RMS noise
of the freq plot data using LadyHeather, backed up by the independent way of
looking at the UNFILTERED 1 sec ADEV values
ws) responses below
***
From: Tom Van Baak t...@leapsecond.com
Long term, really low noise is all about the quality of the GPS signal
and engine.
And the antenna, and the multi-path, and ionosphere, etc. ...
ws) And all the other things that go into making a Good GPS signal
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