[time-nuts] Tbolt issues

EWKehren at aol.com EWKehren at aol.com
Sat Sep 10 08:43:37 EDT 2016

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  
Bert Kehren
In a message dated 9/10/2016 6:42:17 A.M. Eastern Daylight Time,  
csteinmetz at yandex.com writes:

Bert  wrote:

>  would you please share your settings, this is exactly  what we are  
>  for. We are doing it by trial and  error but your expertise will help 

Well, I spent the holiday  weekend looking for the "safe place" where I 
recorded my final Tbolt  tuning parameters -- without success.  After I 
tuned them and  qualified them as fit for long-term duty, I disconnected 
the com ports and  stashed them away in a very quiet and hard to access 
location with just  the 10MHz coax connected, so I can't use the comms to 
extract the  parameters without disturbing the Tbolts (which have now 
settled nicely,  undisturbed for ~10 years).

But what I did wasn't rocket science -- I  just read up on the tuning 
parameters, determined which ones would likely  affect the stability of 
the 10MHz output, made some educated guesses about  the likely best 
settings, and started playing.  It took me several  weeks of 
experimentation (on and off), and the parameters I settled on  were 
somewhat different between the two units I kept (primarily, the loop  
time constant and damping, which ideally should be set to complement the  
particular OCXO in each unit).

I recommend extreme caution when you  hear suggestions to use low loop 
damping, or to monkey very much with the  oscillator scale factor.  I 
found that high damping (far above the  1.2 default value) worked best 
for my units.  (Like you, I care most  about the stability and accuracy 
of the 10MHz output.  I don't even  have the PPS turned on.)

Before you do anything else, I strongly  suggest a full factory reset to 
put everything into a known state, and  work from there.

You have received some advice to use the "autotune"  routine in Lady 
Heather.  I seem to recall several people reporting  that it worked well 
for them, and there is nothing to lose by trying  it.  However, in my 
case it screwed up the tuning of both units so  badly that I had to do 
factory resets and then re-enter my custom  parameters.  I might have 
been using a version of LH that didn't have  the latest autotune code, or 
perhaps the autotune function needs to start  from factory default 
settings, or maybe the phase of the moon was wrong --  but I was sure 
glad I had recorded the tuning parameters I worked out by  experiment, so 
I didn't have to start over again!  Just be prepared  to do another 
factory reset and start experimenting if autotune doesn't  work to your 

So, I would suggest: (1) do a full factory  reset, let it run for a few 
weeks, and take data; (2) use the autotune  routine, let it run for a few 
weeks, and take data.  If you are not  satisfied with the results at this 
point, (3) do another full factory  reset and begin experimenting manually.

Best  regards,


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