WS 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 problem. Bert Kehren In a message dated 9/18/2011 12:24:04 A.M. Eastern Daylight Time, warrensjmail-...@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 is controlled to keep the Heat sink temperature constant ws **************** Bill Harris w7kxb at msn.com Bert: Something to be said about "no moving parts". Bill-w7kxb ********* > 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 last > year using a nice flask that I tested extensively using the guts of a > 10811 > 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 order > to > take advantage of the large overnight changes. Since then I have focused > on > temperature control by fan cooling. Shopping for small fin heat sinks I > ran > across a VGA cooling assembly at our favorite supply site 370537089468 > for > 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, the > back plate was 59.7 C with an ambient of 29.2. the fan assembly without > fan > running was actually already cooling the back plate, because without it > mounted, the temperature was 62 C. 6 minutes after powering up the 12 V > 80 mA > fan, temperature had dropped to 45 C and 30 minutes after power up the > back > 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 with > a > 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 air > temp. > control. Lower temp. will also extend life. > Now my dilemma is whether to use my original design with an array of small > heat sinks with the fan off the side not part of the Rb or stay with this > super simple design. > Bert Kehren Miami _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.