[time-nuts] Different Survey Results

WarrenS warrensjmail-one at yahoo.com
Thu Aug 19 19:32:02 UTC 2010

Peter asked:
>2) Is it necessary to modify Tbolt settings or does tbold work best with 
>factory settings?

The answer is, for best performance you need to modify the factory setting.
There has been much posted on which ones and how, but bottom line is it all 
depend on what your setup is and what you want it to do.

It is a tradeoff to reduce the GPS short term noise and correct for the 
oscillator's long term noise.
The best settings depend on what the noise frequencies and amplitude are in 
the two items and that depends on many things.
The default setting for the Tbolt are meant to be used with a very GOOD 
antenna system and a not so good OCXO in a POOR environment.
My situation is just the reverse. In one of my Tbolt units I'm using a very 
good OSC in a controlled constant temperature environment with a poor indoor 
antenna. The Default setting in this case are a disaster from a best 
performance standpoint.

What I have found to give good general results if you do not want to fine 
tune your specific Tbolt unit and
assuming a typical nut setup in a good environment (which includes adding 
some thermo mass to the Tbolt),

1) change  the TC to 300,
2) the damping to 0.7
3) the Dac gain to -3.0 Hz/V,
4) the Elevation to 20 deg,
5) the AMU to 3.0
6) and then do a 24 or 48 hr survey if you are using Lady Heather
or change the default survey size from 2,000 samples to more like 20,000+ 
samples, to a value that averages over at least 12 hrs, and have it save the 



[time-nuts] Different Survey Results
Peter Krengel krengeldatec at gmx.de
Thu Aug 19 16:28:52 UTC 2010


I'm new to the list and to the themes at all. I'm running a V3 Thunderbolt 
using the great Lady Heather Software (thanks for this).

Setting up the tbold for the first time I made a 48h survey.
To compare the results I also started a SirF III GPS using VisualGPS
software and after the 48h period I got totally different results.

Knowing my real geografic coordinates very well I saw that the tbold
obviously calculated wrong data.

So my questions to the group are:

1. For getting best disciplining results out of the tbold: Do I better
    put in the coordinates manualy or using the survey function?

2. Is it necessary to modify DAC and temperature settings using
    command line options (or using the heather) or does tbold work best with
    factory settings?

3. Is there any "How to.." pdf or book on the net which comes with more
    informations about the tbold experiences than the well known
    official pdf from 2003 ?

Thank you very much for help.

73 from germany
Peter Krengel

More information about the time-nuts mailing list