Introduction to Amateur Satellites

The world of hobbyist satellite building and launching has become increasingly popular in recent years. As a hobbyist project, launching a CubeSat can be an exciting and rewarding experience. However, before you start your project, it's crucial to understand the specific frequencies available. The availability and use of these frequencies depend on the type of satellite and whether it includes amateur radio functions.

Amateur Satellites vs. Amateur Radio Satellites

It's important to distinguish between an amateur satellite and a satellite that uses amateur radio. While both are related, they serve different purposes and are subject to different regulations. In the United States, for example, if you're engaging in purely amateur activities without any compensation, you can potentially use amateur radio frequencies. However, for most hobbyist projects, the process is more complex.

Regulations in the United States

In the U.S., there are two primary approaches for using frequencies:

Amateur Satellites: If your satellite is being built as a purely amateur project and you are not involved in any commercial or educational activities that would involve compensation, you might be allowed to use amateur radio frequencies. However, you will need to coordinate your satellite through a national body (the Radio Society of Great Britain, for example) and the International Amateur Radio Union (IARU). Part 5 Experimental License: For non-government, non-amateur radio small satellites, you will need to apply to the Federal Communications Commission (FCC). This involves a coordination process and receiving specific frequency assignments. The FCC also enforces rules regarding the generation of orbital debris and the detectability of the satellite.

S Band Frequencies

S band is a popular choice for hobbyist satellite projects due to the availability of materials and equipment. Here are the details:

The S band is not automatically open for all amateur radio activities. You must be in a satellite allocation and go through a coordination process to assign specific frequencies. The uplink frequency range is 2.025-2.120 GHz, and the downlink frequency range is 2.200-2.300 GHz. The lower band is shared with TV Studio-Transmitter links (TV live remote). One advantage of S band is the availability of inexpensive and easy-to-use equipment, such as the Analog Devices Pluto SDR, which can receive and transmit S band without any issues. A disadvantage of S band is the ease of using high gain antennas, which can lead to narrow beamwidth and the need for precise pointing. As the satellite moves quickly across the sky in Low Earth Orbit (LEO), pointing a 3-degree wide beam is significantly more challenging than a 30-degree wide beam in the UHF range. There is also a significant risk of interference from the myriad ISM devices operating around the 2.45 GHz frequency, which can affect the amateur radio frequencies in the S band.

Alternatives: C Band and X Band

If the amateur radio frequencies in the S band are not suitable for your project, you might consider using frequencies in the C band or X band:

C band has amateur allocations at 3.4-3.41 GHz and 5.8 GHz. X band has an amateur allocation at 10.45-10.5 GHz.

It's important to note, however, that for S-band satellite frequencies (2.4-2.45 GHz, 2.4-2.403 preferred), there are significant issues with interference from ISM devices. You might be better off going for a Part 5 experimental license and using the "real earth satellite S-band" for your project.

Conclusion

Choosing the right frequency for your amateur satellite project is a crucial step. Whether you choose S band, C band, or X band, familiarize yourself with the regulation and coordination processes associated with each. Remember, the availability of specific frequencies can significantly impact the success of your project.