NOTE: Much of this info is outdated now, it was written over 10 years ago haha!!! I've kept it here for nostalgia or whatever!
If you want a motorised satellite system, you probably want digital, right? Digital receivers now offer Disecq, which allows control over a motorised dish with a suitable mount, using just the LNB cable. More expensive systems offer the traditional 36V actuator controls. Disecq is best for small dishes, while the traditional actuator is the only option for larger dishes (1.2m+). So is there any value left in analogue? Here are a few thoughts:
Analogue will eventually be phased out totally although not for a number of years. Sky have long since discontinued their analogue service. However there are still many analogue channels out there.
A digital receiver is supposedly easy to add to an existing analogue system if it has 'LNB loopthrough', allowing both analogue and digital receivers to share the same LNB. But only one receiver can control the polarity on the LNB (messy). Better to add a dual LNB and run in another cable (this is the way I did it).
If you have an old analogue motorised system with a triple-band LNB you will have to change to a universal for most digital receivers. I mailed What Satellite about this because I was unclear about whether I should keep a triple-band LNB to allow for polarising variations on satellites. Their reply (published in the October 1999 issue) suggested that a universal should work just as well and most likely better since the separate polariser in a triple-band LNB can attenuate the signal slightly. Digital receivers now almost exclusively expect a universal LNB, not sure if any now support the old triple-band ones.
If you're interested in feeds, most of these are now digital (although many are still in the clear).
During the launch of digital TV much was made of the picture quality being excellent. Thing is, that's not all there is to it. Here are a few points worthy of note:
A digital receiver will produce a 'perfect' picture so long as it gets a good signal. If your dish or aerial is not big enough or is out of alignment, the picture may freeze, break up into coloured squares or disappear completely. Whereas poor signal quality on analogue results in a sparkly but watchable picture, poor signal quality on digital will result in the picture breaking up, or in a blank screen.
The digital picture is never truly 'perfect'. Digital TV provides more channels by 'compressing' a number of channels into the frequency space used for just one analogue channel. This means removing some information and although not drastic, the effects can be seen on the picture if you look closely. The more channels that are squeezed into the space of one analogue channel, the more the picture suffers. Sky use up to 8 channels and the picture is still reasonably good ; some frequencies on other satellites have up to 11, which results in poor picture quality. In any case a compressed digital picture cannot normally match the best analogue pictures.