You cannot tune into different satellites, with a single LNB, when your dish is pointing at 13E you can only receive channels from 13E.
A Unicable LNB allows you to do multiple recordings, on different transponders, and still view other transponders, on the satellite your dish is pointing at.
You could fit a bracket, and add a second LNB, 6 degrees apart, so that you can view two different satellites, at the same time, that are 6 degrees apart, or a second, fixed dish system, with multiple LNB's, to view as many satellites, as you can receive, at the same time.
If you only view 13E, and 19.2E, then it might be best to get a fixed dish, with 2 LNB's, and run the requisite cables.