[time-nuts] Tbolt instability

John Green wpxs472 at gmail.com
Thu Oct 8 23:59:54 UTC 2009


Mark Sims wrote:
A lot depends upon the temperature sensor in the Tbolt. ? ?Dallas Semi
changed the guts of the sensor ship in such a way that the Tbolt can only
get 1 degree resolution out of it. ? Later production Tbolts all have that
sensor. ?Does your Tbolt show a mostly flat line temp curve with coarse,
?step-like transitions or one that tracks the temperature rather finely? ?
When you hit the thing with the hot air, ?what did the temperature plot do?

Also, ?the temperature sensor would do no good inside the OCXO (there is
already one in there). ?The Tbolt temperature sensor is used to compensate
the unit for temperature effects on the unit as a complete system. ? It is
also used for environmental alarms, etc.

Mark, Mine is an older unit. I believe it has the better sensor. It seems to
read out temperature to maybe .001 degree. When Lady Heather changed the
temp scale to 10 mDeg/div, I still saw lots of fine steps.
The hot air blast raised the temp 11 degrees C per Lady Heather. I have it
in a corrugated box to insulate it somewhat. I was still seeing large
temperature excursions with the A/C cycling. I diverted the vent over my
work bench and that helped. I finally got LH to report 5E-13 at tau =
10,000. It is definitely temperature that is causing the phase shifts.
I needed a reference for a 900 MHz ham repeater I am building and had been
having trouble finding anything that wouldn't need frequent adjustment. The
Tbolt is the perfect solution to that need,. It should never need attention.


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