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There appear to be at least 1 reasonably high-res (500+ px vertical res) live video stream being transmitted from both the SpaceX F9 first and upper stages all the way up into LEO throughout their launches.

What system of transmission is being used? Which band is used? Where is the transmitter? Is there an external antenna? Where is/are the receiver(s) located?

It seems to transmit mostly uninterrupted video from launch and halfway around the Earth. How do they do it?

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    $\begingroup$ You can hear the acquisition and loss of telemetry signals from the rocket by the ground stations during the livestream e.g. on the launch on 2020/1/29, I heard "AOS (Acquisition Of Signal) Bermuda" and a "LOS (Loss Of Signal) Cape" callouts as it came into and out of range of those ground stations. $\endgroup$ – astrosnapper Jan 29 at 16:49
  • $\begingroup$ Cool! Who runs/owns those, and what frequencies are they? How do the spacecraft reach them? $\endgroup$ – sneak Jan 29 at 17:30
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    $\begingroup$ Looks like a joint NASA/Orbital Sciences (now Orbital ATK, which launches out of NASA Wallops)/SpaceX facility according to info here. The information specifically says "SpaceX use the site to maintain data communications after the go out of range of KSC so the video downlink can show pictures of the Second stage primary burn." $\endgroup$ – astrosnapper Jan 29 at 18:46
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    $\begingroup$ Thanks for the lead, @astrosnapper. I just found this post from 2018 about the renovation, which is neat: nasa.gov/feature/… $\endgroup$ – William Jan 29 at 21:54
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You can get some information from SpaceX's FCC filings for "Special Temporary Authority". There aren't always individual ones for specific launches, because certain approvals cover larger times, and they're a little broken up. For example, 0551-EX-ST-2019 covers transmissions from the first and second stages during flight, while the more-recent 2181-EX-ST-2019 covers communications with the first stage right at landing.

The 0551 STA lists four transmission channels from the first stage and two from the second. The first stage has a 3.57 Mbps 4M14F1D (FM Digitrax telemetry in a 4.14 MHz window) and a 4.167 Mbps 4M84F1D pair of signals at 2209.000 MHz, and an another pair of the same types at 2255.500 MHz. All of the transmitters are (individually) 20W output power; the first pair is 11.8W ERP, the second is 10.8W ERP, so they have slightly different antennae or perhaps cable losses.

The second stage has a pair of 3.57 Mbps 4M14F1D channels. One is at 2232.500 MHz 9.4W ERP and the other at 2272.500 MHz 9.6W ERP.

The STA says that there four transmitters from Quasonix will be used, model numbers "to be provided" (TBP). Quasonix makes a line of dual telemetry transmitters that match up with the frequencies listed.

All up, that's not a lot of bandwidth. Either SpaceX has achieved Pied Piper levels of compression, or there are only a couple of video streams going down to the ground.

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