SimTX Guide/Rotators and tracking

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A rotator turns an antenna on a ground station. Tracking follows a satellite with the rotator and corrects its Doppler shift.

Mounts[edit | edit source]

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[edit | edit source]

Globe over Europe with an Aim Roof Yagi card reading 32°, 2,657 km with Cancel and Done, the current heading line labelled 300°, and a dashed line from Demo hilltop toward the northeast. — Aim on map: a dashed line runs from the station to the pointer, and the card shows its heading and distance.

Rotator control with a compass dial, Azimuth 220, the Aim on map and Use stored heading links, and the line Turning to 220°, about 25 s. — The Rotator dial turning a beam antenna by hand to 220°.

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[edit | edit source]

Track a satellite set to AstroLink, Correct Doppler ticked, In view now, sets 13:32 UTC, and the Rotator switched from By hand to Follow AstroLink, with the satellite's azimuth and elevation. — The rotator following AstroLink, with Correct Doppler ticked.

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[edit | edit source]

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[edit | edit source]

Globe of Europe and North Africa with an orange line from Demo hilltop labelled TX 300°, a blue line labelled RX 180°, 25° up, and dashed lines to satellites in view. — Beam lines from Demo hilltop: TX at 300° and RX at 180°, 25° up.

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[edit | edit source]

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.