A favorite ham activity is making contacts via satellites. There is the idea of sending messages into space, but you also have to follow the orbit of the satellite with your antenna while tuning the radio, to adjust for the Doppler effect.
The satellites orbit the Earth acting as repeaters. Repeaters are relay stations that allow hams to send signals over a greater distance using low-power hand held transceivers. The satellites allow hams to send messages from Earth to space and back to other hams on earth. The International Space Station (ISS) also has a repeater, the astronauts turn on their radio to make contact directly with hams on the ground.
All you need is a VHF/UHF transceiver and an antenna, to get you started listening to the satellites. For better results, you can use a Yagi antenna connected to a mutli-mode radio and a license (if you want to transmit). A Yagi antenna can also be used to improve the received signal of your hand held radio.
Start by visiting Heavens-Above.com to check the orbit of the satellite you want to listen to and indicate your location. Check the passes of your specific satellite or the ISS. Make sure that the passes are shown for your correct location
The Start of a pass(when/where the satellite enters on the horizon), the Max. Altitude (when/where the satellite is at its highest point in the sky), and the End (when/where the satellite finishes it’s pass). The altitude is the angle of the satellite from the observer’s horizon. 0 degrees is exactly on the horizon, and 90 degrees is directly above the observer. The Azimuth is the cardinal direction of the satellite from the observer’s point of view.
Satellite repeaters work with two different frequencies, an uplink and a downlink. You will listen to signals received on the downlink. If you wish to transmit, you’ll need to program in the uplink frequency as well.
When using a Yagi antenna, you do not aim the antenna directly at the satellite. Instead, you’ll keep it perpendicular to the satellite. You can rotate the antenna by rotating your hand to try and get a better signal.
You will trace the path of the satellite orbit with the antenna using the Heavens-Above pass chart as a guide. At the Start Time, start with the antenna perpendicular to the Azimuth. direction at the given Altitude.It can be very difficult trying to catch the satellites and you may spend a lot of time not hearing anything.
The Doppler effect makes the frequency vary by 10 MHz. As you trace the path of the satellite with the antenna, you will also need to tune the radio plus or minus 10 MHz until you hear a good signal.