GoKawiilHobbyist replaces stock fan in Calnex rubidium/GPS frequency reference with Noctua NF-A4x20 FLX
A hobbyist running a Calnex Rb/GPS frequency reference in an 'Atomic Clock Tower' setup documented swapping out the unit's noisy stock Delta EFB0412HHD fan for a quieter Noctua NF-A4x20 FLX. The process involved opening the Loctite-secured case, exposing a SpectraTime GRClok-1500 module and heat-spreader cooling assembly, then splicing wires since the original fan's connector didn't match Noctua's cable ends.
GoKawiil's interpretation of the reporting above, not reported fact.
The write-up is presented as the only documented example of this specific fan swap online, which could make it a useful reference for other owners of similar Calnex timing equipment seeking quieter 24/7 operation. It also illustrates a common tension in precision lab/test gear: manufacturers often prioritize cooling reliability over acoustic comfort, pushing hobbyists toward DIY modifications when such equipment is used in home or office settings.
- A hobbyist swapped the stock fan on a Calnex Rb/GPS frequency reference for a quieter Noctua NF-A4x20 FLX.
- The mod required opening a Loctite-sealed case and rewiring due to a nonstandard fan connector on the Calnex PCB.
- The project is noted as likely the only public documentation of this specific hardware modification.
Noctua NF-A4x10 5V Fan — This is exactly the compact, ultra-quiet fan swap enthusiasts use to silence noisy test equipment like Calnex frequency references. Its renowned low-noise bearing and airflow design make it ideal for 24x7 operation near a desk without sacrificing cooling for sensitive GPS/Rb modules.
See Noctua NF-A4x10 5V Fan on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: jeffgeerling.com, 2026-10-29
Published there as: “Noctua Fan Swap on a Calnex Rb/GPS Frequency Reference”
Read the original report → The summary and analysis above are GoKawiil's own, written from reporting by the source above. Facts and quotes belong to the original publisher.