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Exploring Satellite Communication for Amateur Radio Enthusiasts: Accessing the ISS and Beyond

2,453 words, 13 minutes read time.

https://open.spotify.com/episode/4bgSi0XQEZQHUSMoD2G5CG

Amateur radio has always been a fascinating hobby, offering endless opportunities for communication across the globe. But what if I told you that you could take it even further? Imagine sending a signal from your station that reaches the International Space Station (ISS) or even other satellites orbiting the Earth. This level of communication isn’t just for the professionals—it’s accessible to amateur radio enthusiasts with a little knowledge, the right equipment, and some patience. In this post, we’ll dive into the world of satellite communication, specifically how amateur radio operators can access the ISS and beyond.

Understanding Satellite Communication

Satellite communication, in the context of amateur radio, refers to using satellites to communicate over long distances, often through radio signals relayed by satellites in orbit. These satellites can be either geostationary, meaning they remain in a fixed position above Earth, or low Earth orbit (LEO) satellites, which move across the sky, passing over different locations as they orbit the Earth.

In amateur radio, the most common satellites are LEO satellites, which are ideal for short-range communications but provide exciting possibilities for global contact, such as accessing the ISS. These satellites are often used for Voice or Data transmission, with communication modes ranging from analog FM to digital modes like PSK31 and FT8.

Accessing the International Space Station (ISS)

One of the most thrilling aspects of amateur radio satellite communication is the opportunity to communicate with astronauts aboard the ISS. The ISS serves as an active hub for amateur radio operations through a program called ARISS (Amateur Radio on the International Space Station). This program allows amateur radio operators from around the world to make contact with the astronauts in orbit, provided certain conditions are met.

To get started with accessing the ISS, you’ll need a few key pieces of equipment and some knowledge of how satellite communication works. Here’s a more detailed look at what you’ll need:

1. A Suitable Transceiver

To communicate with the ISS, you’ll need a VHF/UHF transceiver that can transmit on the 144 MHz and 435 MHz bands. These frequencies are commonly used for satellite communications and specifically for operations involving the ISS. The VHF band (144-148 MHz) is used for uplink signals, meaning your signal from Earth to the satellite, while the UHF band (435-438 MHz) is used for downlink signals, meaning the satellite’s signal to you. A good transceiver that supports both of these bands will enable you to transmit and receive signals to and from the ISS.

In addition to frequency capability, it’s important that your transceiver has the necessary features to handle satellite communication. For instance, many amateur radio operators use radios with an Automatic Frequency Control (AFC) function to help mitigate issues with frequency drift, which can be caused by the Doppler effect as the satellite moves. Some radios also have built-in satellite modes that adjust for Doppler shifts automatically, making communication easier during high-speed passes.

2. A Directional Antenna

A directional antenna, such as a Yagi or an Arrow antenna, is essential for satellite communication with the ISS. Unlike a simple omni-directional antenna, which broadcasts in all directions, a directional antenna focuses the signal in one direction. This is critical because the ISS moves rapidly across the sky, and to maintain a strong, stable signal, you must point the antenna directly at the satellite.

The Yagi antenna is particularly popular among amateur radio operators for satellite communication because of its high gain and relatively compact size. If you’re just starting out, there are portable models available that can be easily set up and taken down. When you’re tracking the ISS, you’ll need to continually adjust the antenna’s direction as the satellite moves overhead. Having a high-quality, directional antenna will ensure you get the best possible signal strength and quality during these brief communication windows.

3. Tracking Software and Tools

Since the ISS orbits the Earth every 90 minutes, it will only be in range for a short window of time. To effectively communicate with the ISS, you need to know when it will be passing over your location, and where to point your antenna. Fortunately, there are a number of tracking software applications and websites that can help with this.

One of the most popular tracking tools is the Heavens-Above website, which provides real-time satellite tracking, including the ISS. Additionally, N2YO is another excellent resource for tracking the ISS and other satellites. These websites allow you to input your location and provide you with the exact time and trajectory of the ISS’s next pass over your area. There are also mobile apps available for iOS and Android, such as ISS Tracker and GoISSWatch, which provide real-time notifications when the ISS is about to pass.

Tracking software typically includes information like the satellite’s altitude and azimuth, showing you exactly where in the sky to point your antenna for optimal communication. Some programs even provide Doppler shift predictions, helping you adjust your frequency settings in real-time.

4. A Good Understanding of Satellite Passes

To make contact with the ISS, timing is everything. The ISS orbits the Earth roughly every 90 minutes, meaning it moves rapidly across the sky. Since the satellite only remains in range for a brief period, you’ll need to carefully plan your communication attempts around its pass schedule.

The pass of the ISS is predictable, and knowing when it will pass overhead is crucial to making contact. Each satellite pass lasts only a few minutes, and the ISS’s orbit means it’s constantly moving in and out of range. For example, if you’re trying to communicate via an overpass at the horizon, the satellite will be very low and its signal strength weaker. Conversely, during the overhead portion of the pass, the signal is typically stronger.

Tracking software or apps will show you exactly when the next pass will occur in your location, including the duration and the satellite’s maximum elevation angle. This means you can plan to be ready with your equipment at the right time to catch the best part of the pass.

Additionally, understanding the Doppler shift effect is crucial. As the ISS approaches, its frequency will be slightly higher than the nominal frequency due to the Doppler effect, and as it moves away, the frequency will shift lower. If you’re using a manual system, you’ll need to adjust your frequency settings in real time as the satellite moves. Many modern radios and tracking software can handle this automatically, but it’s something to be aware of if you’re manually tuning in.

5. Other Considerations

While these four components—transceiver, antenna, tracking software, and pass understanding—are the core requirements for communicating with the ISS, there are a few other things to keep in mind:

A stable power supply: Since satellite communication requires a lot of focus and can sometimes take several attempts, ensuring your equipment has a reliable power source is crucial. Consider using a battery backup or a reliable generator if you’re setting up in a remote area.
A quiet environment: Satellite communication can be affected by interference, so a quiet radio environment is essential. Avoid operating near strong RF interference sources like power lines or large electrical equipment.

By carefully preparing these elements, you’ll be well on your way to making contact with the ISS and taking part in one of the most exciting facets of amateur radio. With the right equipment and knowledge, you’ll soon be able to join the ranks of amateur radio operators communicating with the International Space Station!

When the ISS is within range, you can attempt a communication session using a simple “CQ” (calling for any contact) or by listening to the astronauts as they periodically transmit their voice for public Q&A. Make sure to respect the ISS’s frequency allocations and be mindful of the rules for operating in such a unique environment.

Satellites: Exploring Beyond the ISS

While the ISS serves as an exciting gateway for amateur radio enthusiasts to explore satellite communication, it is just the tip of the iceberg. Beyond the ISS, there is a whole universe of satellites to discover. Known as “AMSATs” (Amateur Radio Satellites), these satellites provide a wealth of opportunities for communication with fellow amateur radio operators across the globe. These satellites are often in Low Earth Orbit (LEO), meaning they orbit the Earth at altitudes between 200 and 2,000 kilometers, and they offer unique capabilities for both voice and data communication.

AMSATs operate on a variety of frequencies and modes, providing options for operators of all levels to engage in satellite communication. Some satellites are designed specifically for voice communication, while others are set up for digital modes, and many support a combination of both. These satellites can be used for everything from simple voice QSOs (contacts) to more complex digital modes and data transmissions.

For those new to satellite communication, AMSATs offer an accessible way to extend your range and reach new parts of the world without the need for long-distance ground-based communication systems. Here’s a closer look at some notable AMSATs and how you can access them.

Notable AMSATs You Can Access

AO-91 (RadFxSat-2) AO-91 is a popular amateur radio satellite operating in LEO and is part of the RadFxSat mission. Launched by AMSAT, this satellite is designed to offer both FM voice and digital communications. It’s an excellent choice for newcomers to satellite communication due to its simple, user-friendly FM voice repeater, which is perfect for making voice contacts with fellow ham operators. AO-91 also supports digital communication modes such as BPSK31, a mode widely used for low-data-rate digital transmissions.The satellite has an uplink frequency of 145.880 MHz and a downlink frequency of 435.150 MHz, both of which are common in the amateur satellite community. Its orbit provides a great opportunity for operators to connect during relatively short passes across the sky, making it an excellent tool for practicing satellite communications.
AO-92 (RadFxSat-1) AO-92, also known as RadFxSat-1, is another AMSAT in LEO that provides both voice and digital communications. Much like AO-91, AO-92 is designed to facilitate communication using FM voice repeater capabilities, making it ideal for new satellite operators. In addition to voice communication, AO-92 supports digital modes, including PSK31, which is a popular digital mode for text-based communication over radio.AO-92’s operating frequencies are very similar to those of AO-91, with an uplink frequency of 145.880 MHz and a downlink frequency of 435.350 MHz. The satellite’s regular passes provide reliable opportunities for operators to make contact, and its clear voice capabilities make it a favorite among satellite enthusiasts.
SO-50 (Saudi-OSCAR 50) SO-50 is another LEO satellite that has been in service for years. It is an FM voice repeater satellite, making it an excellent choice for operators who want to make simple voice contacts. The SO-50 satellite has an uplink frequency of 145.850 MHz and a downlink frequency of 436.795 MHz. Although it’s older than some of the other satellites, it remains a reliable choice for operators due to its easy-to-use FM voice repeater and its regular passes over North America and other regions.
FO-29 (Fuji-OSCAR 29) FO-29 is a unique satellite because it supports both analog FM voice communication and SSB (single-sideband) operations, allowing for longer-range, high-quality communication. This satellite is particularly useful for operators who want to experiment with different modes of communication. FO-29’s downlink frequency is 435.795 MHz, and its uplink frequency is 145.850 MHz. While it operates in a higher frequency range than the simpler FM repeaters, it’s a valuable satellite for more advanced operators looking to broaden their skill set.

How to Communicate with AMSATs

Like the ISS, most AMSATs are in Low Earth Orbit, which means they move quickly across the sky and are only in range for a few minutes at a time. To successfully communicate with these satellites, operators need to carefully track their position in real-time and adjust their antennas accordingly to maintain contact as the satellite passes overhead.

Tracking AMSATs

Tracking the position of AMSATs is similar to tracking the ISS, but it requires more frequent adjustments because most AMSATs have shorter passes and may appear and disappear quickly. To do this effectively, you’ll need tracking software or apps, such as Heavens-Above, N2YO, or SatPC32, which can provide precise data about when an AMSAT will pass over your location and where to point your antenna.

These tools offer detailed information about each satellite’s pass, including the elevation (how high in the sky it will appear), azimuth (the compass direction from which the satellite will come), and duration of the pass. Many amateur radio operators use automated antenna tracking systems that can adjust the antenna’s position based on satellite location data, but if you’re manually tracking, you’ll need to be prepared to rotate your antenna during the pass.

Antennas for AMSAT Communication

For satellite communication, a high-gain, directional antenna is essential. Common options for AMSAT communication include Yagi antennas and the Arrow 2m/70cm handheld antenna. These antennas are designed to provide a narrow, focused beam that can be directed toward the passing satellite. Due to the rapid movement of these satellites, operators must continuously adjust their antenna’s direction to keep the signal strong and clear.

Short Passes and Doppler Shift

One of the challenges of communicating with AMSATs is the Doppler effect, which causes the frequency of the satellite signal to shift as it moves relative to your position on Earth. As the satellite approaches, the frequency will be slightly higher than the nominal frequency; as it moves away, the frequency will be slightly lower. This shift can cause issues if you don’t adjust your frequency settings in real-time. Fortunately, most modern radios are equipped to compensate for Doppler shift automatically, but it’s important to be aware of this phenomenon when using older equipment or if you’re manually tuning.

Operating on Satellites

While it’s thrilling to make contacts with satellites, communication on these frequencies requires the same etiquette and consideration as traditional amateur radio operations. Keep your transmissions brief, especially during peak usage times when multiple operators may be trying to access the same satellite. Be patient, listen for your turn, and always be respectful of others on the air.

Conclusion: The Expanding World of AMSATs

Satellite communication in amateur radio is an exciting and expanding frontier, and AMSATs offer an incredible opportunity to communicate with fellow ham operators all over the world. While the ISS is a great starting point, AMSATs like AO-91, AO-92, SO-50, and FO-29 open up even more possibilities, allowing you to explore different modes, frequencies, and communication techniques.

With the right equipment, tracking software, and a little practice, you’ll be able to enjoy the thrill of satellite communication, expanding your reach and exploring new ways to connect with the amateur radio community.

D. Bryan King

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