SimTX Guide/Rotators and tracking
A rotator turns an antenna on a ground station. Tracking follows a satellite with the rotator and corrects its Doppler shift.
Mounts
Set the Mount of each antenna in the station editor.
| Mount | Turns | Rate |
|---|---|---|
| Fixed | Not at all | |
| Azimuth rotator | Around the horizon | 3° per second |
| Az-El rotator | Around the horizon and up to the zenith | 6° per second in azimuth, 4° per second in elevation |
Parks at azimuth (and Elevation on an Az-El rotator) is the stored heading, where the antenna points when a session starts.
Turn an antenna by hand
The Rotator control is in the Station section of the Transmit and Receive tabs when the antenna has a rotator.
- Drag the dial, or type the Azimuth and, on an Az-El rotator, the Elevation. The arrow keys turn the dial 1°, Shift and an arrow 10°.
- Aim on map: the app switches to the Stations tab. Click the globe or a station; the antenna points toward it, level with the horizon. Press Done to keep it.
- Use stored heading turns back to the stored heading.
On the dial, the needle is where the antenna points and the dot on the rim is the stored heading. The line below says what the rotator is doing, for example Turning to 285°, about 40 s.
Off the air, the heading is where the next session starts. On the air, the rotator turns at once. The stored heading only changes in the station editor.
Follow a satellite
- Under Track a satellite, choose the satellite.
- The Rotator control switches to Follow and the satellite's name. Correct Doppler is ticked.
The antenna follows the satellite while it is above the horizon and waits where it will rise. By hand stops following. Choose Off under Track a satellite to stop tracking. On a Fixed antenna, tracking only corrects Doppler.
How the rotator moves
- Each axis turns at its own rate, so a turn takes as long as the slower axis needs. A half turn on an azimuth rotator takes a minute.
- The stop is at north: azimuth runs from 0° to 360° and never crosses north, so 350° to 10° goes the long way round.
- A fast satellite passing overhead can outrun the rotator for a while near its highest point.
The beam line
The globe in the Stations tab draws a line from the station along each rotator antenna's heading, with the heading as its label. It moves as the rotator turns. While you aim on the map, a dashed line runs from the station to the pointer.
The heading on every band
The heading counts for HF skywave and ground wave, VHF and UHF paths, satellite links and the noise the antenna picks up. A beam pointed away from the other station can be weaker than a wire antenna.