[time-nuts] SMPS or conventional

[ew]

Allow me to comment on switchers and Rb cooling. We use in all our projects SMPS with very good results, even on the Dual Mixer which has 1 E-14 at one second. Picture attached. Easier to filter than 50 or 60 Hz. We have also done tests like Mean Well RSD-60 directly in to an OSA 8600. No deterioration. We have Efratom equipment where a M/W powers a LPRO directly only a LC filter. Super performance. The choice of SMP makes a difference. We even use Laptop power modules  with very good results. Not all are the same.

Now to Rb's. First all Rb's can stand clean up. Even the HP5065A can be improved with a OSA 8600 or 8607. Juerg is doing it. Av improvement is in 0.1 to 15 seconds. Juerg used his OSA system to clean up his PRS10 till the lamp circuit burned out which started a 2 year Tbolt project. Take a look at SRS FS740 Av plots, no way I would waste money on their Rb. Just SC cut OCXO does not make it.  Talkedto  SRS to be able to modify the filter and use an other source in the FS740, no way. Otherwise it is a good Swiss Army knife.                                                                         
Spend a year on Fan cooling. We use a Mag Lev fan on the FRK and M100.  Did 3 year aging test. Back plate is 0.01C! measured with a second NTC next to the one controlling the fan. Found out not needed but cooling is a must. The Rb's we have tested they all have some temperature compensation. A small amount of air goes a long way, I did many tests. For some Rb's I prefer heat pipes, be aware you do need a temperature delta to make heat flow. All mine came from ebay and out of Compaq computers. All ours are low noise and you have to test start voltage. We have zeroed in on 34 C back plate, depends very much on what your Lab temperature and application is. Again in all cases we use clean up loop but that depends on what you have in case of OCXO's   May look in to power shut down in case of fan failure                                                                                                                                         Bert Kehren
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