[time-nuts] Rb cooling

[Steve Rooke]

On 18 July 2011 11:12, WB6BNQ <wb6bnq at cox.net> wrote:
> Thinking about it Poul,
>
> That explains why the preferred "frying pan" is made of cast iron in deference to
> the modern light weight ones they sell these days; better temperature control
> across the cooking area.  I knew I was saving old used cast iron pans for a
> reason.  Now I know what I am going to do with them.

OT: They also work well on an induction hob if you ever go that way,
whereas a lot of older style, or cheaper, stainless steel have non
magnetic bases.

Steve

> And I agree, people are not thinking about the reason for the heat regarding the
> Rb.  Everything in its proper balance.
>
> Bill....WB6BNQ
>
>
> Poul-Henning Kamp wrote:
>
>> Cooling Rb's is a much misunderstood discipline.
>>
>> Most Rb's have a specified "base plate temperature range".
>>
>> For instance the PRS10 specifies -20..+65°C
>>
>> Cooling Rb's should happen only through the base-plate.
>>
>> Cooling other surfaces creates unwanted temperature gradients inside
>> the Rb unit.
>>
>> The colder you run a Rb, the more power it uses to keep important
>> bits inside warm.
>>
>> Running it near the top end of the range wears out the electronics
>> in it faster.
>>
>> No matter what kind of cooling, it is important that it offers
>> sufficient cooling capacity for the internal ovens to have a
>> margin to work with.
>>
>> For frequency stability, you should strive to have a constant
>> baseplate temperature.
>>
>> Putting a fan on anything, will generally speed up and amplify the
>> effects of any ambient temperature changes.
>>
>> For optimal frequency stability, you want to do is mount
>> your Rb on a huge lump of iron which you can keep at a
>> constant temperature around 35-40°C by natural convection.
>>
>> Iron is better than Cu/brass/Al because it conducts heat slower and
>> less eagerly, thus attenuating ambient temperature fluctuations.
>>
>> --
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>> FreeBSD committer       | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
>>
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>
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-- 
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein