On Satelight Dish / Direct TV: Why some channels get errors vs. others ?

[RJSV]

    I know the basics, on modulation and some RF concepts, (maybe dated a few years), but simple question about reception:

   Observing that one channel, '287', and maybe another, '290' seem to have very different reception errors and 're-buffering' issues.
   The error mode '771' in our system, is saying there is a Satellite Signal issue.

   But wait...:   In a digital world how is that ?   Why, I'm thinking, why isn't every channel transmitted within a 'single' large channel, rather than style with a 'tuner' in every receiver.

   As I'm writing this, some portion of the answer becomes clear...I think.
That satelight system is broadcasting a multitude of 'channels', that can't really fit, into one, single RF channel....?

    My thought initially was that a receiver would get EVERYTHING, by way of one single RF frequency thus making the RF section with only a single tuning.

Anybody have a brief rundown, on my shortcomings, in assumption(s) ?
Thanks for reading, and for patience.

[BrianHG]

Assuming that the problem is not at the head-end, or in the broadcast, remember that there are up to 24 or 48 transponders across a few satellites in close proximity to each other.  Slight dish alignment errors may favor the reception of for example 12-24 transponders while the remainder will have a weaker signal, filled with data errors.

Each transponder is like a TV channel with a 32Mhz bandwidth.  (Some newer transponders have 64Mhz maybe even higher).  In each transponder's channel, the analog modem's com, (eg: 256QAM modulation) data stream can be over 32megabytes (256 megabits) a second streaming multiple TV channels.  A single satellite can have anywhere between 12 to 48 transponders.  IE, to get 48 transponders with more power, you dish carrier may be using 2 close proximity satellites, each with 24 transponders, one with one polarization, the other with the opposite polarization on their antenna.

The other possibility is local interference from for example, a near by airport radar system.  I used to have a C & KU band analog dish system.  My local airport was around 15km away.  On specific satellites on specific transponders, since it was an uncompressed analog signal, I could see speckles modulating across the screen at regular intervals.  For digital TV, this I would presume would count as data errors.

[RJSV]

   Wow, thanks,  I never would have considered the presence of more than just ONE single satelight !

[BrianHG]

   Wow, thanks,  I never would have considered the presence of more than just ONE single satelight !

Ever so slightly adjusting the East-West alignment of your dish may fix everything up.  That is if your problem isn't from local microwave interference like from my local airport radar system.

[BrianHG]

If your dish is operating at a very shear angle, or is partially blocked by trees, a larger dish  or relocating your current dish would improve reception.

For example, in my old analog days, I'm located on the east coast of north America, and when I tried to receive the west-most satellites with my C-band system, my 6 foot dish got nothing bu snow while my 10 foot replacement worked fine.

I know the small digital dishes are fixed and tune only to specific satellites, but some brands have larger reflector dish replacements offering superior signal gain.