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. Eastern Daylight Time,
csteinmetz@yandex.com writes:

Bert  wrote:

I am quite sure of that

Yes, the PPS is steered by making slight  adjustments to the OCXO
frequency.  But you can make these  adjustments as arbitrarily small as
you want with the setup  parameters.  I run my Tbolts with pretty tight
limits on the  frequency adjustments.

There is no "there" there.  One never makes a frequency  measurement at
just one instant -- the measurement will ALWAYS be done  over a macro
time interval (very often, one second, sometimes 0.1, 10,  100, or 1000
seconds).  We never observe, and have no way to know,  the instantaneous
frequency (as you put it, "the actual frequency at that  moment it goes
into the measuring device") -- so how can we care about  it?  The only
thing relevant (or even meaningful) is the average  frequency during our
measurement interval.

xDEV tells us half of  what we want to know -- how stable our oscillator
is from one measurement  interval to another.  We would also like to know
what frequency it is  wobbling around -- the "centroid" frequency, if you
will (to borrow a  geometric term).  (Mathematicians can argue for days
about which type  of "average" is appropriate here -- the rest of us just
pick one and carry  on.)  ADEV does not tell us this "centroid" frequency
directly, but  it can be extracted from the same measurements we took to
calculate  ADEV.

I think you are being misled by a belief that the linguistic  construct,
"instantaneous frequency," has real meaning in the world.  It doesn't.

Best  regards,

Charles

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Bert wrote:

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
liking.

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,

Charles

Hi

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 sense than the original numbers. Since it is a pre-defined pair of numbers, it is indeed a “one size fits all” solution.

Bob

Bob wrote:

Warren, who I understand provided the algorithms for the autotune
routine, has advocated in a number of list postings damping factors much
lower than what I consider optimal (and in some cases below the factory
default of 1.2).  Also, in the case of my units, the autotune function
adjusted the tuning rate parameter (OCXO sensitivity) for substantially
increased loop gain, which effectively decreased the damping even
further.  So, one of the results [long ago, and with my very small
sample of Tbolts] was to adjust the loop toward and even into instability.

It also seemed to tinker with parameters I didn't expect it to change,
which is why I had to do a hard reset rather than just re-program the
settings that I had changed as a result of my prior experimentation.

Again, I have no idea why it did this, and it is very possible that the
autotune routine on current versions of LH works perfectly and gives an
optimum tuning very painlessly.  But back when I tried it, with my two
Tbolts, it made them pretty much unusable.

No big deal -- just evaluate the operation of your Tbolt after using the
autotune routine, and if you find that it did not produce the results
you hoped for, be prepared to do a hard reset and tune it manually.  If
it works well, then great!

Best regards,

Charles