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Design of LNB rotation device - initial state


I started thinking about the design of an LNB rotation device. I'm not an engineer, so it's quite a challenge for me. That's why I started writing this article at a time when I have practically nothing yet. So some specific suggestions or solutions will come slowly and at longer intervals. But maybe someone will join the discussion and advise me how to do it. I hesitated for a while whether to add this topic here to the Laminas 2700 dish, or rather to the articles on the reconstruction of the EGIS positioner. With its construction, it will be a kind of extension to the existing feedhorn holder at the dish. However, the control will be merged with the positioner control and therefore all software development will be at EGIS. In the end, I decided that the whole device would be single-purpose intended for use with a specific Laminas 2700 dish, so it logically belongs here. Technical articles on the construction of LNB shooting will hopefully diversify the focus of this website and revive it a bit.

In the first phase, I should probably define what such a device should be able to do. But I'll take it from the other end and say straight away what I don't want to use it for. I do not want to replace the polarization switch and therefore rotate the LNB whenever the polarity of the received signal changes. Therefore, I will not even solve the SW link to program items in the receiver preferences. The purpose will be exclusively to adjust the polarization plane during the twin-engine redirection of the dish to another satellite. The SKEW control will therefore be related to the satellite preselection and a third Skew entry for the proposed unit will be added to the current Azimuth and Elevation entries in the EGIS control program memory.

The philosophy will be the same as for the EGIS positioner control. Thus, in addition to automatic resetting by pressing the preset button for the respective satellite, there will also be arrow buttons for manual SKEW settings. But these are things that I will solve only with the control software. First I have to design and build a hardware prototype. By the way, does such a device have an official name? Is it already sold somewhere as a ready-made solution? Or do you all use your own inventions? What do you call them?

And now back to defining the required parameters. The most important will be the range of rotation. I determine this from the value of SKEW extreme satellites, which I could theoretically still receive from my position. In the east, it is a satellite at 92.2 ° E Chinasat 9, which has a SKEW of -39.5 °. In the west, it is a satellite at 58.0 ° W Intelsat 21, which has a SKEW of + 39.4 °. So the minimum shooting range will be -40 ° to + 40 °.

Another important parameter will be the accuracy of the setting. Since I don't have enough experience yet, I don't know how the deviation of the received signal will affect the deviation of the polarization plane by a few degrees. Preliminarily, I would determine the accuracy ± 1 °. Whether this will be enough, or if, on the contrary, this accuracy will be unattainable, it will only become clear in practical tests.


Fig. 1 - LNB holder

For the mechanical construction, I will start from the current state of my Laminas 2700 dish. The existing firm attachment with a plastic sleeve should be maintained for possible alternative use in the future. The new turntable should hold my entire feedhorn system, polarization switch, two LNBs and DiseqC switch in the same place and allow everything to rotate within the designed range. This means that the original arm holding the feedhorn will only be complemented by a few holes for attaching my device with screws.


Fig. 2 - Holder opposite side

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