Practical takeaway
Satellite telemetry, orbits, Doppler shift, uplinks/downlinks, tracking, beacons, spin fading, and power.
T8B · 12 pool questions
Amateur Satellites & Doppler
Satellite telemetry, orbits, Doppler shift, uplinks/downlinks, tracking, beacons, spin fading, and power.
Technician exam focus
This group contains 12 questions in the current pool. The teaching below keeps the important tested terms visible while explaining what they mean in normal Amateur Radio use.
1. Satellites have an uplink and a downlink
The uplink is the frequency path from the ground station to the satellite; the downlink is from the satellite back to Earth. Satellite-tracking software predicts where and when the satellite will be visible from your location.
2. LEO satellites move fast across the sky
LEO means low Earth orbit. Because the satellite is moving rapidly relative to you, the apparent frequency changes from Doppler shift. Operators often adjust frequency during a pass to stay centered on the signal.
3. Beacons carry useful status information
Satellite beacons commonly transmit health and status telemetry. Anyone may receive amateur-satellite transmissions. Transmitting on an uplink requires the appropriate amateur privileges and must follow the satellite’s operating rules.
4. Use only enough uplink power
With a linear-transponder satellite, a practical power check is that your downlink signal should be about the same strength as the satellite beacon. A much stronger signal risks overdriving the transponder and taking capacity away from other users.
5. Spin and motion can change signal strength
As a satellite rotates, antenna orientation changes and can cause periodic fading called spin fading. A fading satellite signal is not automatically a transmitter problem at your station.
T8B checklist
- Uplink = Earth to satellite; downlink = satellite to Earth.
- LEO = low Earth orbit.
- Relative motion causes Doppler shift.
- Satellite beacons commonly transmit health and status telemetry.
- For a linear transponder, keep your downlink signal about the same strength as the beacon.
- Rotation can cause spin fading.
Exam scope: NCVEC 2026–2030 Technician Class (Element 2), effective July 1, 2026 through June 30, 2030, with February 19, 2026 errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool