SimTX Guide/Rotators and tracking: Difference between revisions

Latest revision as of 20:48, 24 October 2026

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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.

@@ Line 1: / Line 1: @@
 {{SimTX Guide navigation}}
-A '''rotator''' turns an antenna. With one you can point a directional antenna at another station or follow a satellite across the sky. '''Tracking''' a satellite also corrects the Doppler shift of its signal.
+A '''rotator''' turns an antenna on a ground station. '''Tracking''' follows a satellite with the rotator and corrects its Doppler shift.
 == Mounts ==
-Each antenna of a ground station has a '''Mount''', set in the station editor:
+Set the '''Mount''' of each antenna in the station editor.
 {| class="wikitable"
-! Mount !! Turns !! Use
+! Mount !! Turns !! Rate
 |-
-| '''Fixed''' || Not at all || Wire antennas, and beams that always point the same way.
+| '''Fixed''' || Not at all ||
 |-
-| '''Azimuth rotator''' || Around the horizon || Beams for HF and VHF contacts in any direction.
+| '''Azimuth rotator''' || Around the horizon || 3° per second
 |-
-| '''Az-El rotator''' || Around the horizon and up to the zenith || Satellites, which cross the sky.
+| '''Az-El rotator''' || Around the horizon and up to the zenith || 6° per second in azimuth, 4° per second in elevation
 |}
-On a rotator, '''Parks at azimuth''' (and '''Elevation''' on an Az-El rotator) is the stored heading: where the antenna points when a session starts. Satellite antennas have no mount; they turn with the satellite's attitude. See [[SimTX Guide/Stations#Antennas|Stations]].
+'''Parks at azimuth''' (and '''Elevation''' on an Az-El rotator) is the stored heading, where the antenna points when a session starts.
-== The Rotator control ==
+== Turn an antenna by hand ==
-When the chosen antenna has a rotator, the '''Station''' section of the '''Transmit''' and '''Receive''' tabs shows a '''Rotator''' control. It has two modes.
+[[File:SimTX Guide Rotators aim on map.png|thumb|center|660px|alt=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.]]
+[[File:SimTX Guide Rotators by hand.png|thumb|center|606px|alt=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.
-=== By hand ===
+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.''
-* Drag the dial to the heading you want. The needle shows where the antenna points; the dot on the rim is the stored heading.
-* Or type the '''Azimuth''', and on an Az-El rotator the '''Elevation''', in degrees.
-* Or press '''Aim on map'''. The app switches to the '''Stations''' tab and the card ''Aim &lt;antenna name&gt;'' appears. Click the globe or a station: the antenna turns toward that point, along the shortest path over the Earth and level with the horizon. Press '''Done''' to keep it, or '''Cancel''' to go back to the old heading.
-* '''Use stored heading''' turns the antenna back to its stored heading.
-With the keyboard, the arrow keys turn the dial 1° at a time and Shift with an arrow 10°.
+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 ===
+== Follow a satellite ==
-Choose a satellite under '''Track a satellite'''. The control then offers '''By hand''' and '''Follow''' with the satellite's name, and selects '''Follow'''. The rotator follows the satellite while it is above the horizon. Before it rises, the antenna waits where it will come up.
+[[File:SimTX Guide Rotators follow.png|thumb|center|606px|alt=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.
-=== Off the air and on the air ===
+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.
-* Off the air, the heading you set is where the next session on this antenna starts.
-* On the air, a change reaches the running session at once, and the rotator starts turning.
-The line under the control says what the rotator is doing, for example ''Turning to 285°, about 40 s.'' or ''Waits at 12°, 0° up until &lt;satellite&gt; rises.''
+== 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 heading you set applies to your sessions. It does not change the stored heading; change that in the station editor.
+== The beam line ==
+[[File:SimTX Guide Rotators beam line.webp|thumb|center|800px|alt=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.
-== Turning speed ==
+== The heading on every band ==
-A rotator turns at a realistic speed:
+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.
-{| class="wikitable"
-! Mount !! Azimuth !! Elevation
-|-
-| '''Azimuth rotator''' || 3° per second || Fixed
-|-
-| '''Az-El rotator''' || 6° per second || 4° per second
-|}
-Each axis turns on its own, so a turn takes as long as the slower axis needs. A half turn on an azimuth rotator takes a minute.
-The rotator has its stop at north. Azimuth runs from 0° to 360° and a turn never crosses north, so a turn from 350° to 10° goes the long way round, through south.
-A fast satellite passing close overhead can move faster than the rotator, so the antenna lags behind it for a while near the highest point. The rotator catches up as the satellite moves away.
-== The beam line on the map ==
-The globe in the '''Stations''' tab draws a line from your station along the heading of each rotator antenna you use, labelled with the heading. It moves while the rotator turns or follows a satellite. While you aim on the map, a dashed line runs from the station to the pointer.
-== Why the heading matters ==
-The direction the antenna points counts on every band:
-* on HF, for skywave and ground wave;
-* on VHF and UHF, for paths along the ground;
-* for satellite links;
-* for the noise the antenna picks up.
-A beam pointed away from the other station can be weaker than a simple wire. While the rotator turns, the signal rises and falls as the beam sweeps past.
-== Tracking a satellite ==
-In the '''Station''' section of the '''Transmit''' or '''Receive''' tab, '''Track a satellite''' lists the satellites in orbit. Choosing one:
-* turns on '''Correct Doppler''', so the frequency follows the satellite's Doppler shift;
-* on a rotator, selects '''Follow''', so the antenna follows the satellite;
-* shows the next pass over the station.
-On a fixed antenna, tracking corrects the Doppler shift but can't point the antenna. Choose '''Off''' to stop tracking. Changes reach a running session at once. [[SimTX Guide/Satellites#Doppler|Satellites]] explains Doppler and passes.
-== See also ==
-* [[SimTX Guide/Stations]]
-* [[SimTX Guide/Satellites]]
-* [[Yagi Antenna]]
-* [[SimTX API/Tracking and pointing]]: rotators and tracking in the developer reference.
 [[Category:SimTX Guide]]