How to Find the International Space Station (ISS) on Ham Radio
The International Space Station (ISS) orbits Earth at an average altitude of about 400 kilometers (250 miles), and it’s equipped with amateur radio equipment that allows ham radio operators around the world to communicate with astronauts on board. Finding the ISS on ham radio can be both a thrilling and educational experience, especially if you are interested in space, science, and ham radio technology. Here’s a step-by-step guide on how to find the ISS on ham radio and start making contacts.
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1. Understand the ISS Ham Radio Frequencies
The ISS operates on several amateur radio frequencies depending on the mode of operation. Here are the most common frequencies and their purposes, as listed by ARISS:
🛰️ Voice Contacts (FM Mode)
🔁 Cross-Band FM Repeater (when active)
- Uplink: 145.990 MHz FM (with 67.0 Hz CTCSS tone)
- Downlink: 437.800 MHz FM
📡 Packet/APRS Digipeater (when active)
- Uplink and Downlink: 145.825 MHz FM
- Used to send APRS messages via the ISS.
📷 Slow Scan TV (SSTV, during special events)
- Downlink only: 145.800 MHz FM
- SSTV images are usually transmitted in PD120 or similar modes.
📺 HamTV (currently inactive)
- Downlink only: ~2395 MHz (S-band digital video)
🔎 Tip: These modes and frequencies can change depending on the mission schedule and hardware status. Always check the ARISS Current Status page before attempting a contact.
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2. Know the ISS’s Orbit
The ISS orbits the Earth approximately every 90 minutes, and it passes over different parts of the planet at various times throughout the day. To catch the ISS during one of its passes, you need to know when it will be visible from your location. You can use online tracking tools to predict when the ISS will pass overhead.
Resources for Tracking the ISS:
- Heavens Above: A popular site for tracking satellites, including the ISS.
- CelesTrak: Provides TLE (Two-Line Element) data and orbital information.
- ISS Tracker Apps: Several smartphone apps, like “Heavens Above” or “GoISSWatch,” provide real-time tracking of the ISS.
These tools and apps will give you the exact times and the trajectory of the ISS’s pass over your area. Some apps even send you notifications when the ISS is visible, so you won’t miss your chance to tune in.
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3. Prepare Your Ham Radio Equipment
You’ll need a ham radio transceiver capable of operating on the required frequencies and modes. For listening to the ISS, you don’t need to transmit, so a receiver tuned to the VHF frequency (145.800 MHz) will be enough.
If you wish to make a contact, you’ll need a transceiver with both the downlink and uplink frequencies and an antenna capable of tracking satellites or working in VHF/UHF bands. Ideally, you should have an antenna like a Yagi antenna or cross-polarized antennas that provide better directional gain.
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4. Understanding Satellite Communication
When communicating with the ISS, it’s important to understand how satellite communication works. The ISS moves quickly across the sky, so you will need to track it as it passes by. Here are some key tips:
- Antenna Tracking: For best results, use an antenna that can be manually or automatically adjusted to track the ISS as it moves. Satellite tracking antennas are ideal for this purpose, but if you’re using a handheld or fixed antenna, you’ll need to move it as the ISS passes by.
- Timing: The ISS passes by relatively quickly, typically within a window of 10-15 minutes. Make sure you’re tuned in and ready before the pass begins.
- Antenna Height: The higher the antenna, the better the reception. If you’re using a handheld radio, try to get outside and away from obstructions like buildings or trees.
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5. Listen for ISS Ham Radio Contacts
When the ISS is overhead, the astronauts onboard may be active on the radio, especially during scheduled contact sessions with schools, amateur radio events, or even casual exchanges. Here’s what to expect:
- Call Signs: The call sign for ISS ham radio operations is NA1SS (North America 1 Space Station).
- Modulation: The ISS uses FM modulation for voice, AFSK 1200 baud for APRS, and PD modes (like PD120) for SSTV.
- Other Modes: Beyond voice, the ISS may transmit APRS beacons, SSTV images, or operate as a cross-band repeater depending on the mission configuration.
- Hearing the Station: You may hear the astronauts calling out their call signs or responding to questions. ISS operations are generally short, and sometimes communication is interrupted by the need to prioritize operational traffic, so don’t be discouraged if it’s difficult to make contact on your first attempt.
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6. Make a Contact
Making a contact with the ISS is a significant achievement, and it usually involves listening for the astronauts’ transmissions and calling them on the appropriate frequency when they pause. Here are a few steps to increase your chances:
Be Patient: Keep in mind that the astronauts are often busy with scientific tasks or communication with ground stations. They may not always be available for casual chat.
Use Simple Language: Keep your exchanges brief and to the point. If you’re attempting a contact, simply call out your call sign and wait for a response.
Timing: The astronauts on the ISS can only hear you when the station is within your radio horizon, so listen carefully for any indications that they’re ready to talk.
Try Other Modes:
APRS Digipeater: Send a beacon via RS0ISS-4 on 145.825 MHz.
Cross-Band Repeater: Make voice contacts when the repeater is active.
SSTV: Receive images during special events on 145.800 MHz.
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7. Join ISS Ham Radio Events
There are scheduled events that involve amateur radio operators communicating with the astronauts aboard the ISS. These events are often organized by educational or amateur radio groups and can be great opportunities to make contact with the ISS.
- ARISS (Amateur Radio on the International Space Station): ARISS is an organization that helps coordinate ham radio contacts between schools and the ISS, giving students a chance to ask astronauts questions. You can follow ARISS’s schedule to find out when these events take place:
👉 ariss.org/current-status-of-iss-stations.html
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8. Record Your Contact and Share the Experience
Making a contact with the ISS is an extraordinary achievement for any ham radio operator. Once you’ve successfully communicated with the station, consider documenting your contact by recording the conversation (with permission, of course) or taking a screenshot of the signal report. You might also want to share your experience with the ham radio community by posting it on forums or social media.
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Conclusion
Finding the ISS on ham radio is a rewarding experience that combines your passion for amateur radio with a deep connection to space exploration. By using tracking tools, preparing your equipment, and understanding the communication process, you can tune in to ISS frequencies and possibly make a direct contact with astronauts in orbit. With patience and the right timing, you could be among the lucky few to chat with the crew aboard the ISS.
✅ Before transmitting, always verify the ISS’s current operating mode and frequency plan at ARISS.org to make sure you’re using the correct setup.
Remember, ham radio is all about community, so even if you don’t make contact on your first try, don’t give up—just keep trying, and enjoy the journey of connecting with space!
