[time-nuts] Achievable temperature stability for Thunderboltenvironment?

WarrenS warrensjmail-one at yahoo.com
Sun Jan 16 23:46:02 UTC 2011

This is the 'KISS' enclosure and driver I use with Lady Heather's temperature controller that holds the temperature change to under 0.01 deg.
I have the box just setting on top of a PC next to the a window.
'KISS' = Keep It Simple and SMALL ...
I don't know if this low resolution picture will post correctly.
If anyone wants a high resolution view of the H/W,
or an expanded plot showing the results over a 2 week period, 
I can provide them, if someone will send me the name of a site to post them at.


> ----- Original Message ----- 
> From: "Mark Sims" <holrum at hotmail.com>
> Sent: Saturday, January 15, 2011 12:53 PM
> Subject: [time-nuts] Achievable temperature stability for 
> Thunderboltenvironment?
> Using Lady Heather's temperature controller (fan+cardboard box+solid state 
> relay+baffling and thermal mass to taste) I get around +/- 3 millidegree 
> temperature control when the AC/furnace is not running and +/- 20 
> millidegrees with them cycling. Long term temperature average is down in the 
> tens of microdegrees. Under ideal conditions, I have seen over an hour where 
> the temperature sensor did not move a single microdegree! The active 
> temperature control has a most definite positive effect on the device 
> performance.
> I place the power supply in the thermal enclosure to minimize its output 
> temperature coefficient. Yes, the thermal sensor is away from the oscillator 
> module (and power supply) but in the semi-closed environment of the box, the 
> thermal stability on one area is pretty much the same everywhere. I have 
> chosen my box so that if the fan stops (for whatever reason) the temperature 
> in the box still does not exceed 50C.
> For the ultra best uber performance you need to maximize the quality of all 
> the input and environmental variables (temperature, power, antenna, surveyed 
> location, disciplining parameters, etc) Choose your antenna mask angle and 
> signal level threshold to minimize satellite constellation switching. With a 
> little nutty attention to the details you can get parts per trillion 
> performance out of the little beastie.
> **********************
> As long as the Tbolt's Osc is being disciplined, I have found:
> Most Tbolt's with factory default settings (i.e TC = 100) will show minimum
> effects with standard room temperature changes. No special protection
> needed.
> A unit that is tuned a bit better (in a box and TC of 300 to 500), then
> temperature changes of less than 1 deg / hr will be OK.
> A better optimized setup with TC settings in the 500 to 1000 sec range, a
> max temperature rate of change  of up to 0.1 deg C per hr will have minimum
> effect.
> If you want to go all out time nuts, (with "Special" TC setting above 1000)
> then best to hold the sensor temperature to within 0.02 deg total change,
> which can be done using Lady Heather's Temperature controller.
> How high you can go with the TC setting, depends on many things, such as how
> stable the Tbolt's Oscillator is. Each setup is different.
> A TC setting of 1000 sec is generally the max you should go. With this
> Tbolt, the best results can be obtained with a 'special' TC setting to 2000
> to 3000.
> Attached is the last 2 weeks of a Lady Heather plot, showing a temperature
> tracking test I did to see how long it takes a Tbolt to learn a new
> environment.
> This unit has a Poor antenna, 1 sec ADEV of 1e-12, Aging of 4 e-12 / day,
> Temp coeff  of 2.5e-10 / deg.
> Have fun
> ws
> ************************
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