Satellites
The Satellite node tunes its decoders to a satellite's downlink and removes the Doppler shift as it passes, so the decoder never has to chase the carrier.
Build a satellite receiver
- Add GPS position. A fixed position is fine for a station that never moves.
- Add Satellite and wire GPS
positionto itsposition. - Search by name or NORAD number, or paste element lines.
- Pick a transmitter in Signal, or tune the downlink on the dial.
- Wire Satellite
controlto each decoder'scontrol.
On auto tuning the radio follows the decoder, as it does for a scanner.
Run the radio only for passes
Wire Satellite control to the Device's control. The radio opens 30 s before the satellite
rises and closes when it sets, so between passes it costs no CPU, USB or network. A recorder
wired the same way records each pass while armed.
A Device with a control wire runs only while a controller says so. Stop on the Device
still wins.
Point an antenna
- Add Rotator and pick its link: a Yaesu GS-232 controller on a serial port, a
Winegard Trav'ler mount on a serial port, or Hamlib rotctld (
127.0.0.1:4533by default). - Wire Satellite
controlto the Rotator'scontrol.
During a pass the rotator follows the satellite. Between passes it waits where the next one rises.
A Winegard link talks to the motor console at 57600 baud, on the ODU debug port or the board's MOT/DCM header. It reads the steps per revolution each motor reports, so SM and LG elevation motors need no setting, and it holds the mount inside its own travel of 445° azimuth and 94° elevation. It reaches the motor console from any menu the mount was left in, and resends a move the console dropped.
| Setting | Does |
|---|---|
| Mode | Track the satellite, point by hand (Manual), Park, or Stop both axes |
| Axes | Azimuth and elevation, or azimuth only |
| Range | 360°, 450° or 540° of azimuth. Past 360° a pass crosses north without unwinding |
| Heading | Compass bearing the mount's 0° azimuth faces, for a mount not set up facing north. Manual and Park take compass bearings |
| Flip | Elevation reaches 180°. Passes over the top, or across the azimuth stop, are followed with the antenna flipped instead of swinging round |
| Step | Moves smaller than this wait, to spare the motors |
Each pass is planned before it rises, so the rotator never has to unwind halfway through.
On the map
Wire Satellite events to Map. It shows the point below the satellite, the footprint where it
is above the horizon, and the ground track half an orbit back and one ahead. The footprint is
brighter while the satellite is above your horizon. Globe in the map settings suits wide
footprints.
Readouts
| Readout | Shows |
|---|---|
| Azimuth | Compass bearing |
| Elevation | Angle above the horizon; green while visible |
| Range | Distance to the satellite |
| Doppler | The shift being corrected, and how fast it changes |
| Send on | The Doppler-corrected uplink, if the transmitter has one |
| Next pass | Time until rise, or until set during a pass, with peak elevation |
| Elements | Age of the orbit data. Warns after 7 days; press the refresh button. |
Orbits come from CelesTrak and transmitters from SatNOGS DB. Both are cached for two hours.
What remains after correction is the radio's own oscillator error and a small orbit error. Decoders that lock onto a carrier, such as DVB-S2, pull that in themselves.