Quote:
Originally Posted by Aspartame
Yeah ok, I understood none of that, and I'm normally ok with technology. I'll stick with Freeview  |
One last try to explain what and how.
First of all the difference between satellite digital and freeview
In freeview all the available tv signals come down a single cable and as you say you can split the signal and everything you connect can recieve anything. The aerial does nothing but gather all the available signals and squirt them down a single coax cable.
Satellite is very different, it comes from satellites which orbit the earth some 22000mls away. Imagine being able to get tv from an aerial from a transmitter that far away. About 50mls is the maximum if you are lucky. The signals are transmitted at a very very high frequency known as microwaves and are extremely weak. Microwaves are too high a frequency to send on a cable and behave in many ways like light. To use these very weak signals they have to be concentrated (collected) and this is done by a reflective dish which has a special surface shape known as a parabula, this bounces the parallel microwaves from space and focusses them into a small space at the focus (In the same way light can be concentrated using a magnifying glass or parabolic mirror)
Now that a concentrated source of microwaves is available the frequency has to be reduced to allow them to be sent down a coax cable to a tv tuner. The gadget that does this is called a lnb (low noise block converter) and this is the equivalent of your normal TV aerial.
Hope you are following this so far as it's about to get a little more technical
Firstly unlike a tv aerial you can fit more than one lnb in a single small box. Four is common (quad lnb) and as it happens four is a very significant number.
For technical reasons each lnb can only handle around one quarter of all the available signals from a satellite and the reciever tells the lnb which quarter it needs to watch the channel you request. Here comes the major difference to your normal aerial, the reciever has to be able to communicate with the lnb. How does it do that, well simply it has to send a signal up the coax to the lnb. (That's why you should turn off a sat box to connect or disconnect the coax connection)
It should now be obvious that the satellite signal from a single lnb can contain only around one quarter of all the available signals at any one time but that the receiver can get any one by simply telling the lnb to switch to a different quarter.
Here we have the explanation why you can't simply split the signal to more than one tuner. Imagine one tuner wanting the first quarter of available channels and the second a different quarter - result electronic chaos - remember the lnb can only do one quarter at once. You can split the signal but as only one tuner can control the lnb the second tuner will only have the same quarter of channels available as the first tuner is requesting.
So how can a load of people in a block of flats get access to all the channels when there is only one dish. The obvious answer is to each flat a seperate lnb. Sadly there is a limit to how many lnbs you can fit on a single dish. So how is it done, remember I said four was a significant number here,s why. To keep other forum members happy
i will refer to the correct type of lnb altough in fact it's just a modified form of quad. If the dish is fitted with a quattro lnb, that again is simply four in one box. What's the difference well each one does not need telling which quarter to work with, its permanently set to one quarter, lnb one the first quarter, lnb the second etc etc. In this way four coax cables come from the dish with a different quarter of the available channels.
All four cables are connected into a very special switch which has lots of outputs (one for each flat). Suppose you are sitting in flat one and want to watch a channel in quarter one. Your sat reciever sends the signal to what it thinks is an lnb. The switch intercepts the signal and simply connects your box to lnb1. Next suppose your noisy neighbour in flat 2 (Or may be the glamourous blonde - we can all dream can't we
) wants to watch quarter 2, well you guessed it the switch connects flat 2 to lnb 2. So all your neighbours can watch any channel at once.
Now we come to the twin tiuner pvr which needs full access to all channels to fully work for both tuners then it should now be obvious that unless you can persuade the glamourous blonde next door to move in with you and bring her precious sat cable with her, you need another cable back to the fancy switch. Is that possible, may be you would have to ask your landlord.
It all sounds very restrictive, but thanks to a happy coincidence by far the majority of freesat channels are concentrated in the first 2 quarters making many more available than might be thought.
For a full list see here
http://www.joinfreesat.co.uk/index.p...with-one-input
In conclusion if you go for the freesat pvr remember that there is nothing to stop you keeping freeview as well, the two are complementary not exclusive