Positioner Setup: improved Autofocus for low symbol rates

It is best to use the auto focus function in the Positioner setup on a transponder with a high symbol rate, 20,000 or higher. But if not available, any symbol rate can be used, of course. However, the timing and delays should be adjusted slightly. It will now take more time to do autofocus on a low symbol rate.

If someone would care to test and commit this patch, please.