[time-nuts] FE-5680A heat sink

Steve Rooke sar10538 at gmail.com
Tue Jun 9 03:04:57 UTC 2009

Calm down Chuck, your doing it again.

2009/6/9 Chuck Harris <cfharris at erols.com>:
> Hi Poul,
> By replying to my reply to Leigh, and clipping out everything
> that I wrote (but my name), you seem to be attributing to me,
> what Leigh wrote.
> You then rephrased my statement about heaters in the physics
> package, restated my statement about extra cooling increasing
> the power drawn by the heaters.
> You then clarified things greatly by advising to not run the Rb
> too hot, but also don't cool it too much.
> ???
> If you have so much to say to the original author, and nothing to
> say about my reply, wouldn't it have been be better to just reply
> to his message, instead of mine?
> -Chuck Harris
> Poul-Henning Kamp wrote:
>> In message <4A2CFCE2.5020107 at erols.com>, Chuck Harris writes:
>>>> I ran the device today for about half an hour, and used an infrared
>>>> sensing thermometer to measure the external case temperature.
>> Be very careful about trusting this:  you need to do some tricky
>> calibrations to get anywhere near precise when you measure metal
>> surfaces.
>> The easy way, is to put a piece of duc[kt]tape on the metal surface
>> and make sure your thermometer can see only that surface.
>> Unfortunately, the tape will also act as insulation, so the result
>> you get is not precise even then.
>>>> It got up to 48 C externally in the physics package area.
>> That's quite normal.
>> Those small Rb's keep the internal temperature constant using
>> heaters, which can raise the temperature and by being able to dump
>> excess heat through their heat-sink to lower the temperature.
>> You shouldn't run your Rb too hot, as this decreases the electronics
>> lifetime and reduces the wiggle-room of the thermal management
>> inside the device.
>> On the other hand, cooling it too much will only increase the
>> power drain for the heaters and increase the thermal gradients
>> inside the unit, likely degrading thermal stability.
>> Poul-Henning
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Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
A man with one clock knows what time it is;
A man with two clocks is never quite sure.

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