[time-nuts] 10811 foam enclosure
EWKehren at aol.com
EWKehren at aol.com
Sun Jan 9 19:00:03 UTC 2011
Thanks for all the info. Agree after my tests on the Tbolt, that is why I
will place large mass around it, will keep it close to ambient and move
slowly.
What is the zero G axis?
Presently oven current is 65 mA down from 95 at room temp so I have room to
go but I will monitor over ambient changes, presently we have lows in the
60's but it has been as high as 82 in the last week.
I try if possible to stay away from any additional heating or cooling, the
only exception is on the Rb's where I experiment with small variable speed
fans and laptop heat pipes in cooling the base plate to 42 C.
Bert
In a message dated 1/9/2011 1:42:19 P.M. Eastern Standard Time,
warrensjmail-one at yahoo.com writes:
>Q) Has anyone experimented with the amount of insulation on a 10811
>oscillator?
a) Look inside a double oven 10811 to see one example of what works.
>Q) None of the hp/Agilent bench test equipment that uses these
>oscillators uses insulation. Perhaps that's a clue.
a) It is not much of a clue, considering that a patent & knowledgeable
time-nuter can get 10 to 100 + better performance out of them.
Look inside a HP Z3801 GPS.
>Q) "how far can you go"
a) One way is to monitor the Oven current. If it goes to near zero you
went
too far.
I've found a 50% to 75% reduction in heater current from its room
temperature value works.
A separate issue is if you are cooking the electronics outside of the oven.
>Q) too much ... can cause over-heating or instability.
a) To see if the oven controller is becoming unstable,
Just monitor the Oven current and plot how it resettles after making
small
changes of a couple volts to the oven voltage or change its case
temperature.
>Q) What is the preferred orientation of the unit.
The Zero G tilt axes. The position that tilting the unit a slight amount
in
any axes causes the freq to shift in the same direction.
comment) What I've found to be very effective is to place a paper towel
around the osc and put it in a plastic baggie to keep it from generating
any
air currents on its own.
Then put that inside of an enclosure that does not have holes, and Hold
the
enclosure's outside temperature constant.
I find this technique works great for both Tbolts and 10811's. Easy to get
10 - 100 to one improvement with a little care.
IMHO, You do not need, or even want, to raise the case temperature of a
Tbolt anymore than absolutely necessary.
Just need to keep the Tbolts case temperature from changing very fast (or
very far).
1 deg F per hr max works OK for most units, or for the extreme time-nut,
go
for 0.1 degC per hr max rate of change.
To do that, I find mass to be more effective than insulation. (you need
some
of both)
I've gotten the best results using Lady Heather's temperature controller
with a small fan blowing air indirectly at the Tbolt's case.
ws
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