[time-nuts] 10811 foam enclosure

Mark Spencer mspencer12345 at yahoo.ca
Sun Jan 9 15:08:34 EST 2011


My experiences placing my thunderbolt board in various insulated containers show little or no improvement over simply putting a cardboard box over it to keep drafts away.   As time allows I'm going to re run some of the tests using my 5370 and an external standard vs relying on the data from the thunderbolt itself but I'm not expecting to see any significant changes.

I've also started to run some tests with disciplining turned off on the thunderbolt and the drift of the ocxo is quite apparent.

I'll likely get a heavy die cast box for my thunderbolt at some point.

On Sun Jan 9th, 2011 2:00 PM EST EWKehren at aol.com wrote:

>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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>
>
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