alt Hacker NewsYou can just look at the airflow charts and buy accordingly?
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> You can just look at the airflow charts and buy accordingly?
Not with Noctua and the likes, not always at least. These fans are quiet, but they are not made of magic fairy dust. They simply max out at lower flow rates than some of the the noisy, high-RPM fans people replace with them. Those 40 mm Noctuas, apart from voltage options, don't really come in many varieties.
It's a trade-off - you definitely lose the upper end of the device's original temperature range, but if it's stable under your conditions - great. How do you find out? Well, you replace the fans and check if it sizzles or not.
And funnily enough, a LOT of equipment these days isn't made with formal thermal design, they simply throw in high-cfm fans and... check if it sizzles. It usually doesn't because there's plenty of headroom. It's loud, but who cares since it's not meant to sit on your bench.
Source: replaced PSU and chassis fans in countless pieces of network and test & measurement equipment.
If you do you'll often find there isn't an equivalent noctua part.
The best way is to measure temps before (ideally over at least 1-2 hours), then to measure temps the same amount of time after and compare.
In the case of this Rb oscillator, it is temperature sensitive, but also built for pretty extreme environments.
I'm not too worried about this particular application, because the clock will be in an air conditioned environment, and I'm monitoring the clock accuracy to +/- 2ns from another GPSDO / rubidium clock. The performance before and after the fan swap is within my measurement noise for 24H, though I haven't done 30+ day measurements and ADEV comparison. Still working on a consistent test setup.