Uploaded May 2024 | Updated September 2026, 1 week ago

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We build a Phase Locked Loop (PLL) FM demodulator for extracting the Apollo downvoice from its subcarrier, using the classic 7046B IC. But in the meantime, as luck would have it, NASA's own S-band receiver's PLL seems to have gone bonkers, and we can't lock to the spacecraft microwave downlink anymore! So we'll get very hands on with PLLs in this episode. Expect a healthy dose of PLL elevator music.

Apollo Comms Playlist: youtube.com/watch?v=v49ucdZcx9s&list=PL-_93BVApb58SXL-BCv4rVHL-8GuC2WGb

Older video on Fractional-N PLLs, used for frequency synthesis: youtube.com/watch?v=z-50pSc_wg8

Links to doc:
curiousmarc.com/space/apollo-s-band-communications
virtualagc.github.io/virtualagc/QuestForInfo.html
ibiblio.org/apollo
ibiblio.org/apollo/Documents/HSI-481260.pdf

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Elevator Music Credit: Crinoline Dreams by Kevin MacLeod

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