On Satelight Dish / Direct TV:     Why some channels get errors vs. others ? - Page 1
Forum section: electronics / general

author: RJSV
author_rank: Super Contributor
timestamp: August 05, 2024, 12:33:01 am
content: 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.

author: BrianHG
author_rank: Super Contributor
timestamp: August 05, 2024, 12:57:07 am
content: 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.

author: RJSV
author_rank: Super Contributor
timestamp: August 05, 2024, 01:13:43 am
content: Wow, thanks, I never would have considered the presence of more than just ONE single satelight !

author: BrianHG
author_rank: Super Contributor
timestamp: August 05, 2024, 01:36:14 am
content: Quote from: RJSV on August 05, 2024, 01:13:43 amEver 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.

author: BrianHG
author_rank: Super Contributor
timestamp: August 05, 2024, 01:41:01 am
content: 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.