Over on his YouTube channel Crazy Danish Hacker has posted a new video that shows how to pick up amateur radio voice signals from the International Space Station (ISS).
Often astronauts on the ISS will schedule times to chat with schools via amateur radio frequencies. This provides an opportunity to learn about radio whilst at the same time allowing kids to talk directly to an astronaut.
If you live in an area that can 'see' the ISS at the same time as the school then you can easily pick up the downlink (astronaut to ground) portion of the conversation while the ISS passes over. The downlink signal is fairly strong, so only a simple antenna is required. In his video Crazy Danish Hacker uses a telescopic whip attached directly to his RTL-SDR which is placed outside with a view of the sky.