[time-nuts] temperature control
EWKehren at aol.com
EWKehren at aol.com
Sun Sep 18 19:13:51 UTC 2011
I did follow your suggestion and installed the original ATT heat sink and
got a base plate temperature of 47 C. Prior to that I did lower the fan
speed by reducing the voltage to 6 V, that increased the base plate to 43 C
but all vibration and noise disappeared. The only way to find out what if any
performance degradation occurs is with a D/M measuring A/V. Once I have
software for my D/M I will conduct tests with different Rb/OCXO combinations.
My goal remains the same, the best in long term and short term performance
in a GPS Rb OCXO combination.
This test was more of what can be done and the amazing part to me was how
little moving air will make a difference. I will stay with my 5X5X1 cm
vibration mounted fan that sits to the side of the Rb moving air across an array
of small heat sinks with circular fins unless A/V tests tells me I have a
In a message dated 9/18/2011 12:24:04 A.M. Eastern Daylight Time,
warrensjmail-one at yahoo.com writes:
Advantages and Trade-offs both ways
For a simple "no moving parts" version,
Oversize the heat sink and attach a 10 Watt resistor to it whose voltage
controlled to keep the Heat sink temperature constant
Bill Harris w7kxb at msn.com
Something to be said about "no moving parts".
> From: EWKehren at aol.com
> Date: Sat, 17 Sep 2011 21:22:30 -0400
> To: time-nuts at febo.com
> Subject: [time-nuts] temperature control
> Recent comments on dewier flasks bring me back to test I conducted
> year using a nice flask that I tested extensively using the guts of a
> as a constant heat source. What I found and reported was that the ambient
> inside changed as much as .4 C with 8 C changes on the outside. The tests
> ended when it fell off the pedestal that I mounted on my balcony in
> take advantage of the large overnight changes. Since then I have focused
> temperature control by fan cooling. Shopping for small fin heat sinks I
> across a VGA cooling assembly at our favorite supply site 370537089468
> a total of $5.92. At that price I said what the heck. It came in 4 days
> and I mounted it on the back of a FRS. After 4 hours without cooling,
> back plate was 59.7 C with an ambient of 29.2. the fan assembly without
> running was actually already cooling the back plate, because without it
> mounted, the temperature was 62 C. 6 minutes after powering up the 12
> 80 mA
> fan, temperature had dropped to 45 C and 30 minutes after power up the
> plate is 40.6 C again with 29.2 ambient. The fan is very quiet and it is
> amazing what can be done with a small amount of moving air. This fan
> single op amp will be able to hold the back plate within .1 C at 45 C.
> Eventually all my time/frequency units will have some kind of moving
> control. Lower temp. will also extend life.
> Now my dilemma is whether to use my original design with an array of
> heat sinks with the fan off the side not part of the Rb or stay with
> super simple design.
> Bert Kehren Miami
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