[time-nuts] Airflow around oscillators.

Brooke Clarke brooke at pacific.net
Sun May 22 12:44:39 EDT 2005

Hi David:

Years ago I got a Gibbs rack size double oven frequency standard for a 
song because the double ovens were not working.  Upon disassembly it was 
found that the gel cell batteries stored in an adjacent box put acid 
fumes into the air and the printed circuit boards in the oven had their 

The PRS-10 needs to be mounted to a heat sink, either the factory finned 
one or a sizable slab of metal.  Do not run it free standing.

Have Fun and keep us posted,

Brooke Clarke, N6GCE
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml

David Kirkby wrote:

> I am building a GPS locked oscillator and will have in the box the 
> following.
> 1) GPS receiver
> 2) 24 V linear power supply I have had sitting here for ages - a use for 
> it at last!!
> 3) PRS10 rubidium
> 4) 10811-60111 quartz
> 5) 2 x 7 Ah 12V sealed lead acid batteries.
> 6) Shera board, to lock the 10811 to either the rubidium or GPS 
> (interesting to see what gives best performance)
> 7) A couple of DC-DC converters to give other voltages necessary for the 
> Shera board. This seems more sensible than separate power supplies, due 
> to my desire to have battery backup. I don't want a battery for +5V, 
> another for -5V etc.
> 8) A small amount of control logic, to sequence the ovens on the quarts 
> and rubidium, as I can't have both heating up at the same time, although 
> they can both run together later.
> I need to keep the batteries cool, so are planning on blowing cool air 
> over them and around to the power supply.
> I'm wondering if its best to try to reduce the airflow around the 
> 10811-60111 and PRS10 (rubidium) to a minimum necessary to keep the 
> things within temperature, or is airflow over them not going to be an 
> issue? That would make life a bit easier, if I can ignore that.
> I'm also thinking of using a thermostatically controlled fan, in an 
> attempt to keep the temperature inside the box a constant. The unit will 
> *not* be run in a temperature controlled environment, but one in which 
> there are quite large changes in temperature.
> Whilst I don't mind experimenting with such things
> a) Whether the theromostaticaly controlled fan gives smaller or larger 
> changes in the rubidiums base temperature (it has a sensor which can be 
> read.
> b) What gives the best performance (10811 or PRS10)
> c) What it is best to lock the 10811 to (GPS or PRS10)
> I am not too keen on treating this lot as mechano and trying every 
> possible combination of component placement. Once placed, they will stay 
> there, with the exception of perhaps some thermal insulation and the 
> location of a temperature sensor for the fan if used.
> Any thoughts?

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