[time-nuts] Poor man's oven
kb8tq at n1k.org
Wed Jun 7 17:28:07 EDT 2017
The crystal enclosure may (or may not … who knows ..) be back filled with a low level
of helium. It does not take much of a backfill for conduction inside the crystal holder to
dominate the heat transfer vs radiation transfer.
> On Jun 7, 2017, at 5:21 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
> On 6/7/2017 1:09 PM, Attila Kinali wrote:
>> makes the PI loop better behaved. Also the thermal mass of the
>> crystal holder is quite small. Especially compared ot the 10811.
> Actually, the oven mass of the E1938A is much heavier than the
> 10811 and is made of copper to boot.
>> Due to the flat puck design, I assume that the majority of the
>> heat going to the crystal holder is due to radiation (unless I
>> missed some insulation around the crystal). Radiation, albeit being
>> a high "resistivity" transport mechanism, has very low inherent
>> "capacitance". And thus the delay associated with this transport
>> mechanism is low.
> The crystal case is well connected to the oven mass and gets
> heated by conduction. I don't think radiation is a player.
>> There are probably a lot more small design decisions in the E1938
>> that make it such a superb oven. More than I probably will ever
>> be able to figure out. And, I still am astonished how well it works.
>> Attila Kinalid
> Rick N6RK
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