A system for receiving a signal from one or more satellites or transmitting a signal to one or more satellites, the system comprising: - a frame, - a signal converter for converting between received radiation or radiation to be transmitted and a corresponding electrical signal, the converter being positioned, in relation to the frame, rotational around a predetermined axis, - a depolarizer mounted, in relation to the frame, rotational around the predetermined axis, - a single rotator rotationally engaging a first of the converter and the depolarizer and for rotating the first of the converter and the depolarizer in relation to the frame, - means (2, 41) for releasably fixing the depolarizer in relation to the converter and at a predetermined rotational relationship, - a first end stop, and - a second end stop, wherein: - the other of the converter and the depolarizer comprises a part positioned so as to: - engage the first end stop and stop rotation of the other of the converter and the depolarizer when at a first rotational relationship along a first rotational direction and in relation to the frame - engage the second end stop and stop rotation of the other of the converter and the depolarizer when at a second rotational relationship in relation to the frame and along a second rotational direction opposite to the first rotational direction, the first and second rotational relationships defining a predetermined angular interval and - the first of the converter and the depolarizer is rotatable to positions outside of the predetermined angular interval. - a frame, - a signal converter for converting between received radiation or radiation to be transmitted and a corresponding electrical signal, the converter being positioned, in relation to the frame, rotational around a predetermined axis, - a depolarizer mounted, in relation to the frame, rotational around the predetermined axis, - a single rotator rotationally engaging a first of the converter and the depolarizer and for rotating the first of the converter and the depolarizer in relation to the frame, - means (2, 41) for releasably fixing the depolarizer in relation to the converter and at a predetermined rotational relationship, - a first end stop, and - a second end stop, - the other of the converter and the depolarizer comprises a part positioned so as to: - engage the first end stop and stop rotation of the other of the converter and the depolarizer when at a first rotational relationship along a first rotational direction and in relation to the frame - engage the second end stop and stop rotation of the other of the converter and the depolarizer when at a second rotational relationship in relation to the frame and along a second rotational direction opposite to the first rotational direction, the first and second rotational relationships defining a predetermined angular interval and - engage the first end stop and stop rotation of the other of the converter and the depolarizer when at a first rotational relationship along a first rotational direction and in relation to the frame - engage the second end stop and stop rotation of the other of the converter and the depolarizer when at a second rotational relationship in relation to the frame and along a second rotational direction opposite to the first rotational direction, the first and second rotational relationships defining a predetermined angular interval and - the first of the converter and the depolarizer is rotatable to positions outside of the predetermined angular interval.