--- title: From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP... description: A homelab enthusiast documents achieving ±26 nanosecond time accuracy using a $20 Oscilloquartz OSA-5401 GPS-disciplined PTP grandmaster SFP module paired with... canonical: https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP Module Beat My Entire NTP Setup | daily.dev og:description: A homelab enthusiast documents achieving ±26 nanosecond time accuracy using a $20 Oscilloquartz OSA-5401 GPS-disciplined PTP grandmaster SFP module paired with... og:url: https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4 og:image: https://api.daily.dev/og/posts/RRAgkOls4.png og:image:alt: From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP Module Beat My Entire NTP Setup og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP Module Beat My Entire NTP Setup **[Lobsters](https://daily.dev/sources/lobsters)** · 13 min read · 0 upvotes · 0 comments ## Summary A homelab enthusiast documents achieving ±26 nanosecond time accuracy using a $20 Oscilloquartz OSA-5401 GPS-disciplined PTP grandmaster SFP module paired with a Raspberry Pi 5. The setup uses ptp4l to discipline the Pi's hardware PTP clock, then chrony to discipline the system clock. Key findings include: a chrony 'trust' flag bug that prevented switching to the better PTP source, a measured 58.3 μs MCU delay in the GPSDO's PPS output path (corrected with a static offset), and honest analysis showing ±40–50 ns typical vs the headline ±26 ns post-filter figure. The result is ~45x better accuracy than the previous GPS PPS + NTP setup, at roughly $100 total hardware cost. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [This DIY Time Server Is More Accurate Than You Need](https://daily.dev/posts/this-diy-time-server-is-more-accurate-than-you-need-n03z229m5) · Hackaday · 1 upvotes · 0 comments - [Rebuilding a 1995 GPS Time Server so I don't get Telstra'd](https://daily.dev/posts/rebuilding-a-1995-gps-time-server-so-i-don-t-get-telstra-d-hxt9qcyvw) · Jeff Geerling · 2 upvotes · 0 comments - [Owning the system clock: Good enough?](https://daily.dev/posts/owning-the-system-clock-good-enough--ky2rinbzk) · Red Hat Developer · 0 upvotes · 0 comments - [World's Most Stable Raspberry Pi? 81% Better NTP with Thermal Management](https://daily.dev/posts/world-s-most-stable-raspberry-pi-81-better-ntp-with-thermal-management-ta2csuocv) · Hacker News · 1 upvotes · 0 comments - [Technology Used by Optical Atomic Clocks May Jump From Lab to Consumer](https://daily.dev/posts/technology-used-by-optical-atomic-clocks-may-jump-from-lab-to-consumer-kvhdaqak1) · The Quantum Insider · 0 upvotes · 0 comments --- Tags: [#raspberry-pi](https://daily.dev/tags/raspberry-pi) [View this post on daily.dev](https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP Module Beat My Entire NTP Setup","url":"https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4"},"datePublished":"2026-04-27T13:31:30.136Z","dateModified":"2026-04-27T13:32:10.592Z","description":"A homelab enthusiast documents achieving ±26 nanosecond time accuracy using a $20 Oscilloquartz OSA-5401 GPS-disciplined PTP grandmaster SFP module paired with...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/72f32664db41f2132cccc809971d801b?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/72f32664db41f2132cccc809971d801b?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Lobsters","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Lobsters","logo":"https://media.daily.dev/image/upload/s--tl8v_Fku--/f_auto,t_logo/v1698841318/logos/lobste.jpg","url":"https://daily.dev/sources/lobsters"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/from-milliseconds-to-26-nanoseconds-how-a-20-ebay-sfp-module-beat-my-entire-ntp-setup-rragkols4","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"raspberry-pi","timeRequired":"PT13M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Lobsters","item":"https://daily.dev/sources/lobsters"},{"@type":"ListItem","position":3,"name":"From Milliseconds to 26 Nanoseconds: How a $20 eBay SFP Module Beat My Entire NTP Setup"}]} ```