Question about Freesat signals

I am confused about satellite TV signals. With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder.

In what way is my understanding wrong? Is it that only one channel at
a time is available on any one LNB? If this is the case, would that
same channel be available on any decoder in the setup? How can one
combine Freesat signals with DTT in a home distribution system?

On Sat, 22 Aug 2009 15:28:54 +0100, ChrisW
wrote:

I am confused about satellite TV signals. With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder.

In what way is my understanding wrong? Is it that only one channel at
a time is available on any one LNB? If this is the case, would that
same channel be available on any decoder in the setup? How can one
combine Freesat signals with DTT in a home distribution system?

The way to do it is with a Multiswitch fed by a Quattro LNB. Note
"quattro" not "quad".

A multiswitch can supply many separate feeds to individual decoders
(Freesat boxes)s.

For example I have a Triax TMPR 5 x 8 Multiswitch in my house. The 5
refers to 4 inputs from a quattro LNB and 1 input from a terrestrial
aerial. The 8 refers to the number of separate outputs. Each ouput is
distinct from the others. You can be watching or recording 8 different
things at once.
http://www.triax.co.uk/?alPage=&rkPage=&articleId={41D13EE6-2A3A-481C-8E5A-A8C3D37DA700}

I currently use 5 of the outputs - 2 each to 2 Freesat recorders and 1
to a non-recording Freesat box. I don't currently distribute the
terrestial TV signals through it, but this might change sometime.

--
Peter Duncanson
(in uk.tech.digital-tv)

ChrisW wrote:
: In what way is my understanding wrong? Is it that only one channel at
: a time is available on any one LNB? If this is the case, would that
: same channel be available on any decoder in the setup? How can one
: combine Freesat signals with DTT in a home distribution system?

You are missing the fact that, unlike a terrestrial aerial, a LNB is an
active component! In addition to needing DC power to run it each LNB can also
be in one of four possible states - horizontal or vertical polarisation
AND either high or low band - and this is controlled by the STB (using voltage
and tone switching). A quad-LNB, for example, is effectively 4 LNBs in
one housing - each can be in a different state!

You would need the system flats use. A different type of LNB (quattro rather
than quad??) supplies each of the 4 possible states into a multiswitch. Each
STB can select the exact band it wants from this multiswitch using normal
means.

On 22 Aug, 15:28, ChrisW wrote:

I am confused about satellite TV signals. *With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. *I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. *I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder. *
In what way is my understanding wrong? *Is it that only one channel at
a time is available on any one LNB? *If this is the case, would that
same channel be available on any decoder in the setup? *How can one
combine Freesat signals with DTT in a home distribution system?

As none of the experts have replied yet .... here goes.

When you tune a satellite receiver to a channel, the LNB moves into
one of its four ranges:- Horizontal Upper, Horizontal Lower, Vertical
Upper or Vertical Lower so that it can receive that channel.

Which means that other receivers cannot get channels on the other
ranges. Each receiver needs its own LNB to be able to operate
independently. The easiest way for four or fewer receivers is to get
a quad LNB and wire each receiver up individually.

For more that four you can get a switch with four inputs and a greater
number of outputs. Each receiver can be switched through to
whichever of the four ranges it needs.

HTH

ChrisW wrote:
I am confused about satellite TV signals. With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder.

In what way is my understanding wrong? Is it that only one channel at
a time is available on any one LNB? If this is the case, would that
same channel be available on any decoder in the setup? How can one
combine Freesat signals with DTT in a home distribution system?

Satellite is a little different to terrestrial broadcast, the LNB is
part of the receiver and has a switching signal that selects the
polarisation. This is a way of packing the channel closer together
without them interfering. As you go up the frequency the channels are
on alternating polarities. So for 1 polarity selection you only get
half the channels available at a decent level on one LNB.

You can have 2 LNB systems (one for each polarity) and distribute those
around the house with 2 cables, but you then need a separate selector
box that switches 2 cables to each receiver, or each receiver needs to
be able to have 2 dish/LNB feeds and select internally.

I'm not sure what quad LNBs are for, no doubt someone else will answer.
Maybe for more signal, or different satellites or different bands.

You can't generally mix satellite and terrestrial raw signals on the
same cable, likely they would interfere. The alternative to multiple
cables is one sat receiver with an RF modulator and use a carefully
chosen frequency and put that on your terrestrial network. You then use
some sort of remote repeater to control the satellite box. The Sat
signal then appears as one analogue TV channel.

--
Tony

"Peter Duncanson" wrote in message
...
On Sat, 22 Aug 2009 15:28:54 +0100, ChrisW
wrote:

I am confused about satellite TV signals. With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder.

In what way is my understanding wrong? Is it that only one channel at
a time is available on any one LNB? If this is the case, would that
same channel be available on any decoder in the setup? How can one
combine Freesat signals with DTT in a home distribution system?

Two tricks are used to maximise the bandwidth from the satellite two your
dish.

1. There are two bands of ~1GHz each. These are mixed down to a single band
between ~1GHz and 2Ghz (which is about the limit of what you can get down a
cable).

2. The signals are sent in horizontal and vertical polarity, without the
polarity the channels would overlap somewhat and you would get adjacent
channel inteference. Only one polarity can be sent down the wire at once.

Essentially the receiver tells the LNB which band and polarity it wants (by
volts and tones). In a multi-switch all four are sent from the dish to the
switch and the selection is made inside the switch.

Have a butcher's on Wiki.


The way to do it is with a Multiswitch fed by a Quattro LNB. Note
"quattro" not "quad".

Depends on your switch - the latest EMP Centauri can cope with either.

Emerging technology is going to use fibre to send the whole lot down a
single fibre.


A multiswitch can supply many separate feeds to individual decoders
(Freesat boxes)s.

For example I have a Triax TMPR 5 x 8 Multiswitch in my house. The 5
refers to 4 inputs from a quattro LNB and 1 input from a terrestrial
aerial. The 8 refers to the number of separate outputs. Each ouput is
distinct from the others. You can be watching or recording 8 different
things at once.
http://www.triax.co.uk/?alPage=&rkPage=&articleId={41D13EE6-2A3A-481C-8E5A-A8C3D37DA700}

I currently use 5 of the outputs - 2 each to 2 Freesat recorders and 1
to a non-recording Freesat box. I don't currently distribute the
terrestial TV signals through it, but this might change sometime.

--
Peter Duncanson
(in uk.tech.digital-tv)

On Sat, 22 Aug 2009 16:06:18 +0100, Tony wrote:

You can't generally mix satellite and terrestrial raw signals on the
same cable

Of course you can.

likely they would interfere.

They use completely separate frequency bands. It is not "likely". It is
completely unlikely.

The alternative to multiple
cables is one sat receiver with an RF modulator and use a carefully
chosen frequency and put that on your terrestrial network. You then use
some sort of remote repeater to control the satellite box. The Sat
signal then appears as one analogue TV channel.

For God's sake, this is a completely mad solution.

On 22 Aug, 19:49, Paul Ratcliffe
wrote:
On Sat, 22 Aug 2009 16:06:18 +0100, Tony wrote:
You can't generally mix satellite and terrestrial raw signals on the
same cable

Of course you can.

likely they would interfere.

They use completely separate frequency bands. It is not "likely". It is
completely unlikely.

The alternative to multiple
cables is one sat receiver with an RF modulator and use a carefully
chosen frequency and put that on your terrestrial network. *You then use
some sort of remote repeater to control the satellite box. *The Sat
signal then appears as one analogue TV channel.

For God's sake, this is a completely mad solution.

But it is the way that all Sky receivers do it when they are fed
through RF distribution and operated with "magic eyes".
The main reason to do it this way with Sky boxes, however, is to make
the box viewable in various rooms without having to have more than one
subscription. There are, of course, no subscriptions with Freesat so
its much better to have extra receivers in other rooms for channel
flexibility.

There is no reason why a quad LNB cannot be used and diplexers used to
combine its outputs onto four of the downleads from the aerial amp, to
four rooms, and then diplex wall plates to seperate the aerial and
dish signals by the tvs. Each room then has an aerial feed to the TV
and a sat feed to a Freesat box.
This is a bit less tidy than a multiswitch but is potentially cheaper
if the aerial distribution amp is already in place.

"Peter Duncanson" wrote in message
...
On Sat, 22 Aug 2009 15:28:54 +0100, ChrisW
wrote:

I am confused about satellite TV signals. With DTT I feed the signal
from one aerial into a distribution amplifier and the signal and all
channels are then available to any of the amps distribution points. I
am told that for satellite one needs a separate LNB for each TV set -
dual and quad LNBs seem to be common. I was planning to feed a single
Freesat signal into the Sat input of a suitable distribution amp and
was expecting the Freesat signal to be available at all distribution
points and to be available wherever I had a suitable decoder.

In what way is my understanding wrong? Is it that only one channel at
a time is available on any one LNB? If this is the case, would that
same channel be available on any decoder in the setup? How can one
combine Freesat signals with DTT in a home distribution system?

The way to do it is with a Multiswitch fed by a Quattro LNB. Note
"quattro" not "quad".

A multiswitch can supply many separate feeds to individual decoders
(Freesat boxes)s.

For example I have a Triax TMPR 5 x 8 Multiswitch in my house. The 5
refers to 4 inputs from a quattro LNB and 1 input from a terrestrial
aerial. The 8 refers to the number of separate outputs. Each ouput is
distinct from the others. You can be watching or recording 8 different
things at once.


Or for less cost you could put up 2 dishes, each with a quad LNB
to give you those 8 outputs

A multiswitch is only worth bothering if you want more outputs
or can't put up more than one dish

Steve Terry

"Paul Ratcliffe" wrote in message
...
On Sat, 22 Aug 2009 16:06:18 +0100, Tony wrote:

You can't generally mix satellite and terrestrial raw signals on the
same cable

Of course you can.
And this is how virtually every TV distribution system works.


likely they would interfere.
There's a small problem with this at the top end of the UHF band but it is
easily and routinely solved by filters in the multiswitches and wallplates.

Bill