[time-nuts] 10811 foam enclosure

[WarrenS]

>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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