Section 7.4: Amateur Satellite Operation #

Alright, space cadets, strap in for a journey to the final frontier of ham radio - satellite operation! Yes, you heard that right. As a Technician, you can communicate through satellites orbiting hundreds of miles above Earth, extending your radio’s reach beyond the horizon and potentially around the globe. How cool is that?

Key Information:
According to FCC Part 97, a space station is an amateur station located more than 50 km above Earth’s surface.
Any amateur holding a Technician class or higher license can communicate through amateur satellites.
Any amateur holding a Technician class or higher license may contact the International Space Station (ISS) on VHF bands when it passes overhead.

What are Amateur Satellites? #

Amateur satellites, often called “OSCAR” (Orbiting Satellite Carrying Amateur Radio), are like space-based repeaters. They receive signals on one frequency (uplink) and retransmit them on another (downlink). It’s like playing cosmic ping-pong with your radio waves!

Key Information:
A LEO satellite is a satellite in Low Earth Orbit, typically between 100 to 1,200 miles above Earth.
When a satellite is operating in “U/V mode,” the satellite uplink is in the 70 centimeter band (UHF) and the downlink is in the 2 meter band (VHF).
Amateur radio satellites commonly use multiple transmission modes including SSB, FM, CW, and data.

These space speedsters zip around Earth and pass overhead several times a day. A “pass” refers to the portion of the satellite’s orbit when it’s visible from your location on Earth - when it’s above your horizon and you can communicate with it. Each pass typically only lasts 5 to 15 minutes, so you’ve got to be quick! Most amateur satellites are LEOs (Low Earth Orbit satellites), which makes them accessible to operators with modest equipment.

Satellite Beacons and Telemetry #

Key Information:
A satellite beacon is a transmission from a satellite that contains status information about the health and status of the satellite.
Anyone may receive telemetry from a space station - these transmissions aren’t encrypted and are meant to be monitored by amateur operators worldwide.

Satellite beacons are special transmissions that satellites send out regularly, like a space-based lighthouse. These beacons typically transmit telemetry data that can include battery voltage levels, temperature readings, operating mode, and spacecraft orientation.

Satellite Signal Characteristics #

Key Information:
Spin fading of satellite signals is caused by rotation of the satellite and its antennas.
Doppler shift in satellite communications is an observed change in signal frequency caused by relative motion between the satellite and Earth station.

As a satellite rotates in space, its antennas change orientation relative to Earth, causing the signal strength to vary periodically - almost like a cosmic lighthouse effect. This phenomenon, called spin fading, is why satellite operators need to be aware of the satellite’s rotational characteristics.

With Doppler shift, as the satellite approaches, the frequency appears higher, and as it moves away, it seems lower - just like the changing pitch of a passing train’s whistle. This means you’ll need to adjust your frequency during the pass to compensate for this effect.

Tracking and Operating Satellites #

Key Information:
Satellite tracking programs provide maps showing the real-time position of satellites, pass timing information, and the apparent frequency including Doppler shift effects.
These programs use Keplerian elements as inputs - a set of numbers that describe the satellite’s orbit.
Using excessive uplink power can block access to the satellite by other users.
Your signal strength on the downlink should be about the same as the beacon to ensure your uplink power is appropriate. This means you should listen to your own signal as it’s retransmitted by the satellite and compare it to the strength of the satellite’s beacon signal. If your signal is much stronger than the beacon, reduce your power; if it’s weaker, you might need to increase power or improve your antenna pointing.

Here’s what you need to know to get started:

Frequencies: Most ham satellites operate on VHF and UHF bands, right in your Technician wheelhouse. You’ll often use one band for uplink and another for downlink.
Tracking: Satellites move fast! You’ll need tracking programs to know when they’re passing overhead. These programs use mathematical formulas for predicting where a satellite will be at any given time.
Antennas: While you can make some contacts with a handheld and its stock antenna, directional antennas work much better for satellite communications.
Power: Unlike terrestrial repeaters, you don’t need much power. Always use just enough power to make contact. Too much power can actually cause problems for other users trying to access the satellite at the same time.

Types of Satellite Operations #

Amateur satellites support various types of operations:

FM Satellites: Great for beginners. They work just like a repeater in the sky.
Linear Transponder Satellites: These receive a range of frequencies in one band and retransmit them in another band.
International Space Station (ISS): The ISS often has amateur radio equipment onboard, allowing astronauts to make contacts with Earth-bound hams.

Satellite operation might seem daunting, but it’s incredibly rewarding. Start by listening to familiarize yourself with satellite passes before transmitting. Use tracking software to plan your operations, and always be mindful of your power levels.

Remember, every time you make a satellite contact, you’re participating in a grand space adventure - using technology orbiting Earth at thousands of miles per hour to chat with fellow hams. Now that’s taking your radio hobby to new heights!