[time-nuts] Achievable temperature stability for Thunderboltenvironment?

David Hooke dhooke at gmail.com
Sun Mar 31 18:42:22 EDT 2013

Hi All,

I've setup a TBolt with a late model oscillator mounted externally to 
the case, and moved the C version temp sensor from the main PCB to the 
oscillator. With a little fan, LH is keeping the temperature within 
about 0.02dC. Amazing, given I have about 10dC ambient variations.

How do I start LH with the PID parameters obtained during the autotune 

Which bit of which source file should I look at to figure this out?

Thanks to Mark, John, Warren and others for LH!


On 17/01/2011 9:49 AM, WarrenS wrote:
> Here is a Plot of the results, (The post would not accept both pictures at the same time)
> 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.
> ws
> ***************
>> ----- Original Message -----
>> From: "Mark Sims" <holrum-PkbjNfxxIARBDgjK7y7TUQ at public.gmane.org>
>> 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
>> ************************
> >

More information about the time-nuts mailing list