One of my favorite things to do is talk with other ham radio operators through satellites or the International Space Station (ISS). To do this, I stand on a rooftop and tune a handheld multiband radio while tracing the orbit of a satellite or the ISS with my homemade yagi antenna.
Orbiting satellites such as AO-51, SO-50, and AO-27 act as repeaters, relaying signals from low-power transceivers like mine back to hams elsewhere on the planet. So if you know where to aim the antenna, you can communicate around the world via space. The ISS also has a repeater, and occasionally, when we’re lucky, the astronauts themselves exchange transmissions to communicate with hams on the ground.
To listen to these signals from space, you don’t have to be a licensed ham radio operator, or even stand on the roof. You can do it in your own backyard with an off-the-shelf UHF FM radio. The whip antenna on the radio might let you hear satellites and the ISS, but you’ll get far better reception by making your own yagi antenna, which takes about an hour and costs less than $25 (not including the cost of your radio) using materials from your local hardware store.
If you do have a ham radio license and a UHF/VHF transceiver, you can upgrade this antenna with VHF elements so that it can both send and receive transmissions.
A yagi antenna has three types of elements, consisting of metal rods of varying lengths and quantities. The driven element is a dipole antenna that’s connected to the radio and receives the signal, just like a whip antenna. The reflector is positioned behind the driven element, where it acts as a mirror by bouncing signals from the satellite forward to the driven element. Directors are one or more rods that act like a lens, focusing the incoming signal onto the driven element. Both the reflector and the directors improve reception from whatever direction the antenna points.
The antenna design I use comes from Kent Britain’s (WA5VJB) "Cheap Antennas for Low Earth Orbit" (available at wa5vjb.com/references.html), which is a great reference for building many different types of yagi antennas.