Satellite communication has become open to most, if not all, Amateur Radio operators around the world using simple equipment that some already have in their personal inventories. Low Earth Orbit (or LEO) satellites are being built with increasing numbers that are carrying FM repeaters and FM digital equipment that operate in the common 2m uplink and 70cm downlink or Mode-J. Because these satellites are in lower orbits, amateurs with handheld and mobile radios can use these satellites as repeaters in the sky.
One new technology being implemented is the Automatic Position Reporting System or APRS(R). This allows the amateur to send a short burst of data that includes the station's call sign, position, type of station, and some text up to the satellite. There it will be received and digipeated (digitally repeated) back to Earth for many other satellite operators to receive. APRS makes it possible to have many "conversations" going on over the satellite, simultaneously, without disrupting the rest of the operators.
With the equipment that is available today, there really isn't any excuse why more amateurs aren't out there enjoying these resources. Newer radios including handhelds that will interface to both mobile and handheld GPS units, and will automatically update their position. Digital messages have been sent to and from stations using this simple setup allowing amateurs who are hiking, camping, or have antenna restrictions to join in and exchange messages with other hams hundreds or thousands of miles away. One ham even used APRS to beat a speeding ticket by showing the judge she couldn't have [been] speeding because APRS recorded her speed over that stretch of road as many miles per hour less.
Currently, there are two satellites active that support APRS; NO-44 (PCSAT) and the ISS, both of which can easily be used with mobile and handheld radios. At the time of this being written, both satellites are orbiting the earth listening to 145.825MHz and waiting to hear an APRS formatted packet. Using a handheld such as a Kenwood D7A(G) dual-band handheld radio will allow amateurs to transmit position information packets up to the satellite or ISS and monitor messages from other users. The stock antenna will work, higher-gain antennas will add to your fun! Antennas like the Arrow (or similar) and the Pryme AL-800 make excellent satellite antennas for not only APRS but for voice communications too. Unlike other satellites both NO-44 and the ISS work on 2M only, so a dual band radio is not required for APRS.
NO-44 orbits at approximately 750km about(sic) the earth. With a digipeater up that high you can expect your packets to be heard for thousands of kilometers. Usually you can operate on this satellite for about ten minutes per orbit. Bulletins are transmitted on the terrestrial APRS frequency (144.390MHz) when the satellite is overhead and in good working order. See the AMSAT Web site for more information.
The International Space Station is also available for APRS. Orbiting at approximately 350km above the Earth, the ISS doesn't have as big of a footprint as NO-44. The ISS digipeater is shared with the ISS BBS so it is a little more difficult to use as there are more users on the uplink.
APRS is a fun mode to use but why not take it to the next level and utilize equipment for a completely different experience. If a one-hop QSO that would land your packet over 3000km away doesn't sound like fun, then I don't know what does!
For additional information on amateur satellites, check out the following Web sites:
Project OSCAR - http://www.projectoscar.net
AMSAT - http://www.amsat.org
ISS APRS Log - http://www.findu.com/cgi-bin/ariss/index.cgi
PC Sat APRS Log - http://www.findu.com/cgi-bin/pcsat.cgi
WB4APR's Website - http://web.usna.navy.mil/~bruninga