[time-nuts] Thunderbolt oven / non-stable operating temperature
tmiller at skylinenet.net
Mon Dec 10 22:29:32 UTC 2012
The temperature you are seeing is that of a Dallas IC mounted on the main PC
board. You are seeing the ambient temp of the board, not inside the OCXO
----- Original Message -----
From: "Sarah White" <kuzetsa at gmail.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Monday, December 10, 2012 5:15 PM
Subject: [time-nuts] Thunderbolt oven / non-stable operating temperature
Ended up with a gently used trimble thunderbolt a few months ago, and
been trying to figure out the best settings to use (time constant,
damping, etc.) for best performance.
I got distracted though. There is something which I find rather
annoying, and I'm spending more time messing with this factor than
actually observing the performance at different damping / time constant
The temperature seems to be aprox 20C above ambient temperature rather
than a steady 40C. I thought the purpose of the oven was to keep the
temperature stable. When I adjust the thermostat because I'm chilly, the
thunderbolt gets warmer too (but not by as much)
I've tried (seemingly, to me) everything:
putting the unit in a spot away from drafts
putting the unit in a place away from drafts in a shoebox with light
insulation with a fan blowing in it (currently in a cupboard in this
state, and the temp seems to fluctuate the least, but still by more than
1-2 degrees centigrade)
I feel like shouldn't need to fuss with ambient conditions this heavily
for an OCXO, and find myself researching construction / design for a DIY
outer-oven to wrap the thunderbolt in.
Anyone have experience with non-stable temperature on a trimble thunderbolt?
I've also noticed (monitoring with Lady Heather's Disciplined Oscillator
Control Program v3.10 by John Miles aka KE5FX) the thunderbolt unit
sometimes flags an alarm briefly (and I rarely ever manage to write it
down before the screen updates or the alarm goes away) and the last one
I was able to "catch" before it went away was related to temperature.
Should I be getting a steady / non-flucturating 40C or something if the
oven is working normally?
Thanks in advance,
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