Interesting comment copy-pasted from Reddit user felixfelix: "For those unfamiliar with amateur radio, the card shown at 2:41 of the video is a QSL Card. These

Interesting comment copy-pasted from Reddit user felixfelix: "For those unfamiliar with amateur radio, the card shown at 2:41 of the video is a QSL Card. These are little post cards that are normally sent through the mail to confirm that a two-way communication took place. These normally have details about the location and construction of the radio facility. But in this case, there's a summary of the construction of the space station! Finally, "73" (said by the guy in the video, and written on the QSL card by the astronaut) is a telegraph code for "Best Regards""