Section 7.4: Amateur Satellite Operation #

Buckle up, space cadets — 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. Yes, really.

Key Information:
According to FCC Part 97, a space station is an amateur station located more than 50 km above Earth’s surface.
The control operator of a station communicating through an amateur satellite or space station can be any amateur allowed to transmit on the satellite uplink frequency. In practice, this means any Technician class or higher operator, since the bands typically used for satellite uplinks are within Technician privileges.
Any amateur with a Technician class or higher license may contact the International Space Station (ISS) on VHF bands.

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:
LEO stands for Low Earth Orbit, which has a period of around 100 minutes.
When a satellite is operating in U/V mode, the uplink is in the 70-centimeter band and the downlink is in the 2-meter band.
Amateur radio satellites commonly use SSB, FM, and CW/data modes.

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 — typically reporting the health and status of the satellite.
Anyone may receive telemetry from an amateur radio satellite.

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. These transmissions aren’t encrypted and are meant to be monitored by amateur operators worldwide.

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 real-time satellite position maps, pass timing, and apparent frequency including Doppler shift.
The primary input to a satellite tracking program is the Keplerian elements — a set of numbers that describe the satellite’s orbit.
Using excessive effective radiated power on a satellite uplink can cause blocking access by other users.
To check whether your uplink power into a linear transponder satellite is appropriate, your signal strength on the downlink should be about the same as the beacon.

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.

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.

Satellites are one of the most spectacular things you can do with a Technician license, but they’re far from the only kind of fun on offer. The next section covers a few more — including one that involves chasing hidden transmitters around a park.