Can You Hear Me Now? Lunar Edition
Freeman writes:
https://hackaday.com/2022/05/16/can-you-hear-me-now-lunar-edition/
Despite what it looks like in the movies, it is hard to communicate with astronauts from Earth. There are delays, and space vehicles don't usually have a lot of excess power. Plus everything is moving and Doppler shifting and Faraday rotating. Even today, it is tricky. But how did Apollo manage to send back TV, telemetry, and voice back in 1969? [Ken Shirriff] and friends tell us part of the story in a recent post where he looks at the Apollo premodulation processor.
[...] [Ken] takes us through each module. The voice and data detector module extracted voice on a 30 kHz FM subcarrier. There's also a bi-phase modulator, voice clipping, and a relay module to pass signals from the lunar module back to Earth.
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