The SO-50 (Saudi-OSCAR 50) satellite is a popular satellite among amateur radio operators worldwide. Launched on December 20, 2002, SO-50 is one of the most accessible amateur radio satellites in Low Earth Orbit (LEO), providing a reliable platform for satellite communication. This article explores the key features of SO-50, how to access it, and tips for making your first contact.
Overview of SO-50
SO-50, also known as SaudiSat-1C, was built and launched by the Kingdom of Saudi Arabia. It is a small, cube-shaped satellite with a simple repeater on board, allowing radio amateurs to communicate with each other. It orbits the Earth at approximately 650 km altitude, completing one orbit roughly every 90 minutes.
Frequency Information
The SO-50 satellite operates as an FM transponder with the following frequencies:
- Uplink Frequency: 145.850 MHz (FM, PL tone: 67.0 Hz)
- Downlink Frequency: 436.795 MHz (FM)
It’s essential to note that a 67.0 Hz PL tone must be transmitted on the uplink frequency to activate the transponder. This tone is used to wake up the satellite’s repeater and keep it active during your transmission.
Accessing SO-50
To work SO-50, you need a few basic pieces of equipment:
- VHF/UHF Dual-Band Transceiver: A portable or base station dual-band radio capable of operating on the uplink and downlink frequencies.
- Handheld Yagi Antenna or Arrow Antenna: A directional antenna that provides enough gain to ensure clear transmissions, even with the satellite’s relatively low power output.
- PL Tone Encoder: Ensure your transceiver can transmit a 67.0 Hz PL tone, as it is crucial for accessing SO-50.
Operating Procedure
Here’s a step-by-step guide for making a contact through SO-50:
Check the Satellite’s Pass: Use satellite tracking software or apps like AMSAT-DL, Heavens-Above, or Orbitron to determine when SO-50 will be overhead. Look for passes where the satellite is at a higher elevation, as these tend to provide the best signal.
Program Your Frequencies: Enter the uplink and downlink frequencies into your radio. Remember to include the 67.0 Hz tone on the uplink frequency.
Listen First: Before transmitting, listen to the downlink frequency to see if other operators are already using the satellite. This helps avoid interference and ensures efficient use of the transponder.
Make Your Call: Once the satellite is overhead and you have a clear frequency, announce your call sign and grid square. For example: “K6ABC, DM12, calling through SO-50.” Keep your transmission short, as many other operators may be waiting for their turn.
Tips for Successful Contacts
Practice aiming your antenna. A directional antenna, such as a handheld Yagi, is essential for making reliable contacts through SO-50. Practice tracking the satellite’s path to get comfortable pointing your antenna in the right direction.
Adjust for Doppler shift. As SO-50 moves quickly across the sky, the Doppler effect will cause a shift in frequency. Adjust the downlink frequency as the satellite moves to maintain a clear signal.
Use pass predictions. Plan your contacts around high-elevation passes to maximize the time the satellite is within range and to minimize signal blockage from obstacles like buildings or trees.
Troubleshooting Common Issues
If there is no signal on the downlink, ensure your radio is transmitting the correct PL tone (67.0 Hz) on the uplink frequency. Without this tone, the satellite’s transponder will not activate.
Weak or fading signals could be due to the satellite’s position or your antenna’s orientation. Adjust your antenna direction and make sure you have a clear line of sight to the satellite.
Etiquette and Operating Standards
Like all amateur radio operations, using satellites like SO-50 requires good operating practices. Keep transmissions short; the satellite is a shared resource, and many operators may be trying to access it. Short, efficient transmissions help maximize usage. Avoid excessive power, as using more power than necessary can cause interference and may even block other operators. A modest power level with a good antenna setup should suffice. Be patient and courteous, respecting others on the frequency and waiting for your turn to make a contact.
Conclusion
SO-50 remains a fantastic opportunity for amateur radio enthusiasts to practice satellite communications and connect with others worldwide. Whether you’re an experienced operator or just getting started in the world of satellite radio, mastering the techniques to access SO-50 can be a rewarding experience. Happy DXing!
Further Resources:
see you on SO-50!
