why can't you split a sky feed?

[dibbers]

i was reading a post the other day and i can't find it now, was something i've been meaning to ask for a while, it was about a communal dish on a block of flats, so there's like 100 flats in a block with a sky dish on the roof and all the flats have a connection to it (which is active) - but i was reading that you can't split the feed into one of the flats into 2? how come they split it on the roof and do 100 feeds?

Thanks it's just been puzzling me that's all.

TIA.

 

[witchy]

Depending on the channel you are watching, your feed will be either polarised vertical or horizontal, if you are tuned into a vertical transponder then you can only tune into other vertical signals. I'd don't see any reason why you cannot split the feed except that you would need to watch channels on the same polarity.

 

[dibbers]

i kinda follow but still can't understand it, suppose all 100 flats had a dream box then they'd be able to watch any channel? is there something in the box on the wall of these sky feeds that do the vertical/horizontal thingy ma bob?

 

[nozzer]

From the point of view of the customer equipment, it will think its directly connected to an lnb but in reality it will be connected to a switch. This switch will then connect to one of four lnb's depending on the voltage (14v/18v to select polarity) and tone (to select Hi/lo band) given out by the customer equipment.

At any one time any particular customer cable will only connect to one particular fixed lnb so will only be capable of getting the signals from 1/4 of the available spectrum. If you were to split the cable then any 2nd box would only be able to pick up channels that are on the same polarity/band as the main box. The 2nd box cannot control the voltage/tone as that would interfere with the switch.

To transmit everything down one cable at the same time would require quite a bit of magic. Each of the outputs of the four lnb's would need to be remodulated to a different non-overlapping frequency range before being fed into the cable and, at the other end, would then need to be re-mapped back to their proper ranges so the customer box could then select which of the 4 ranges it actually wants. You would then need to duplicate the re-mapping circuitry for each box you wanted to hang off the end of that cable.

 

[dibbers]

ah thanks, nice one Witchy and Nozzer, so each flat once there sky system is connected uses it's very own range for that paticular feed to the property so that's why you can't then split the feed as it's "tuned" as to speak. makes sense now....

 

[Liam1611]

Unfortunately Nozzer is wrong, all the residents will be connected to a Multi-Switch, something like this. Each output of a Quad or Quattro LNB will be fed into the Multi-Switch along with Terrestrial/FM & DAB feeds. The Multi-Switch then combines all these signals known as Multi-Plexing down a single cable, and as all the above signals use different frequencies (Satellite being the highest) it all works together and on the other end of the cable will be a wall socket which then splits the signals back into how they were fed into the Multi-Switch. Each output is independent of each other and to have more than one feed would require you to run an extra cable from the switch to the apartment. Although there are other ways to get 2 satellite feeds down one cable such as this, but they aren't cheap and you would need access to the distribution switch to allow you to "split" the feed. As the Multi-Switches are cascadable, you can add more Multi-Switches and in turn feed more apartments. It's all quite simple really.

Regards

Liam

 

[nozzer]

Unfortunately Nozzer is wrong, all the residents will be connected to a Multi-Switch, something like this. Each output of a Quad or Quattro LNB will be fed into the Multi-Switch along with Terrestrial/FM & DAB feeds. .......

Which is pretty much exactly what I was describing although I deliberately kept 'other' signals out of the description in an attempt to simplify.

If you read what i've written I attempted to describe how the 'switch' selects one of the four possible ranges with each range being catered for by one of the four lnb's (the fact that all four lnb's is in one physical box is neither hear nor there - they are functionally four seperate lnb's). The switch itself 'locks' each of the four lnb's onto one of the four possible ranges - thus covering the whole spectrum (frequency & polorisation) !!!

 

[witchy]

Which is pretty much exactly what I was describing although I deliberately kept 'other' signals out of the description in an attempt to simplify.

I still prefer my uber simple explanation.

 

[MFCGMFC]

or my uber uber simplest explantion

Naw dibbers ye just canny dae it!

Cheers
MFCGAVMFC

 

[dibbers]

or my uber uber simplest explantion

Naw dibbers ye just canny dae it!

Cheers
MFCGAVMFC

Cheers gav me old sparra....

i knarr that nee like afta reading aboot it man....ha!

im slowly making a mend mate! normal service should resume shortly...lol

 

[justintime]

sorry to jump in on this, but i was going to ask a similar question. not in a flat but i am getting a signal error & failed recordings, will a dual lnb, or shotgun cable fix this problem?