November 3, 2025
Hot clock, hotter comments
Inside An Isotemp Oven Controlled Crystal Oscillator
Flea-market “hot clock” sparks a homelab temp-control war
TLDR: A $5 oven-heated clock module was tested and runs at 5 MHz, sparking a debate: homelab fans say cheap temp controllers make the oven old news, while purists insist the oven still rules for true stability. It matters because precise timing underpins everything from lab measurements to communications.
A $5 score from the Silicon Valley Electronics Flea Market has the timing nerds buzzing. The author grabbed a chunky oven-controlled crystal oscillator (think: a tiny clock that keeps itself warm to stay accurate) and got it humming at 5 MHz, the retro frequency beloved by old-school atomic clocks. It slurps power to heat up, then settles down and stays steady—at least after a week. The community chaos kicked off fast: one camp is cheering the thrift-store glory and the “earthquake-hardened” bench vibes, while a loud homelab crew says, “Why bother with an oven?” They argue you can just slap on a cheap temperature controller and get near-perfect stability for pocket change. Purists fired back that an oven-controlled oscillator isn’t just about holding a temperature—it’s about long-term time sanity. They also teased the 5 MHz vs. 10 MHz divide: vintage charm versus modern convenience. Memes flew about the “chonker” oscillator needing a personal thermostat and jokes that the metal case is “boss-level sealed” after the failed opening attempt. The vibe: nostalgia-fueled engineering meets homelab pragmatism, with everyone timing their hot takes by the second. The only thing hotter than the oven? The comments
Key Points
- •An Isotemp OCXO107-10 OCXO with a 5 MHz output was purchased and bench-tested.
- •The unit uses a DE-9 connector (power/control) and an SMA output; the 5 V rail is only for the TTL output.
- •On startup, the 12 V oven rail drew ~320 mA (~3.8 W), settling near 69 mA; Vref measured 6.78 V.
- •Measured 5 MHz output was -1.80 dBm into 50 Ω with a second harmonic at -55.04 dBm (~-53.23 dBc).
- •EFC tuning required ~2.228 V after two days; full stabilization is expected after about a week.