Weather satellite sounds: the tick-tock that went silent
A NOAA weather satellite sounded like a steady tick-tock, two ticks a second, over a buzzing tone; each tick was one line of a cloud picture. That sound went silent in August 2025. The weather satellites still heard near 137 MHz send a digital hiss instead.
What does it sound like?
What was APT?
Automatic Picture Transmission: an analog picture signal that NOAA's polar weather satellites sent for decades, two lines a second, so anyone with a simple antenna and a radio could receive cloud pictures as the satellite passed.
Why it stopped
The last three satellites were switched off in 2025: NOAA-18 on June 6, NOAA-19 on August 13, and NOAA-15, launched in 1998, on August 19. No satellite sends APT any more.
What you can hear now
Russia's Meteor-M satellites still send pictures near 137.1 and 137.9 MHz, in a digital format called LRPT. It sounds like a flat hiss or roar rather than a tick-tock. Passes last 10-15 minutes, several times a day.
Easily confused with
- Weather fax: a similar steady tick, but on shortwave
- ISS SSTV: warbles in pitch rather than holding a steady tone