Beginners Guide to LEO Satellites
This page will cover topics such as satellite hardware, orbits, frequencies, doppler, operating techniques, satellite tracking.
As with any specialised or technical endeavour, the language of amateur satellites is filled with terms, abbreviations, shorthand's, and acronyms that become second nature to those who use them daily, but can be obscure to newcomers -- or even to old hands who begin to explore new aspects of satellite construction or operation. When confused by an unfamiliar batch of "alphabet soup," consult the Acronyms list
A detailed, but somewhat dated beginners guide and other resources may be found at https://www.amsat.org/introduction-to-working-amateur-satellites/
The easiest satellites to work, from a technical standpoint, are the FM satellites. They are essentially single-channel repeaters in space. So while they are relatively easy to hear and to access, they are also very busy, with many stations attempting contacts on the single channel during the short time the satellite is overhead. This can make them somewhat frustrating to work from an operational standpoint. Nevertheless, the FM satellites are a good place to begin.
Currently operational FM satellites include:
- AO-91 (RadFxSat / Fox-1B), SO-50 (SaudiSat-1C)
- PO-101 (Diwata-2 -- available by a varying schedule)
- AO-27 (Currently on for four minutes on ascending and descending passes over mid-latitudes of the Northern Hemisphere)
- IO-86 (LAPAN-A2) In equatorial orbit, activated by schedule
- Several additional FM satellites are currently in orbit undergoing per-commissioning, or soon to be launched.
While it is possible to make contacts through these satellites with a single, dual-band (2m/70cm) hand-held FM radio, it is highly desirable to have "full-duplex" capability -- that is, to be able to hear the satellite at the same time that one is transmitting to it. A few radios on the market have this capability, but they are generally more costly. Many beginners fulfill the requirement using two, less expensive radios -- one for transmitting and the other for receiving. Also, some sort of small, directional antenna is necessary, along with some means to aim it at the satellite as it passes overhead. For beginners, the aiming of the antenna is often done simply by hand. More advanced stations make use of electric motors to rotate the antennas both horizontally (azimuth) and vertically (elevation), often under computer control. More on that later.