The Quasi-Biennial Oscillation — the ~28-month heartbeat of the equatorial stratosphere — read directly from balloons. Within ~10° of the equator the annual cycle in stratospheric zonal wind nearly vanishes, so a monthly multi-station mean of radiosonde winds at 10–100 hPa is the QBO: westerly and easterly regimes descending about 1 km/month. Built from 13 stations (Singapore, Kuala Lumpur, Bintulu, the Micronesia chain, five Amazon stations, Nairobi) — the same raw archive behind the Sounding Explorer.