Two inputs for Sky+

Well, why does Sky+ need 2 co-ax inputs from the dish?

The answer would be: "It has 2 tuners, mate" or "think of it as 2 boxes,
pal" or "you would need 2 feeds to 2 rooms with 2 people watching different
channels, sky+ is the same, mate".

OK, but what about Freeview and cable............a Freeview PVR only has one
aerial input but can have 2 tuners and perform the same functions as a sky+
box. A Telewest "TV Drive" Cable PVR only has one co-ax input but has
multiple tuners and performs the same functions as a Sky+ box.

Why can the Sky+ box not work quite happily with one feed from the dish? Was
the Sky+ box designed so that it requires 2 feeds. Could it have been
designed like the Telewest box so that it only needs one
feed................or is it something to do with the frequency of the sat
signal, making it difficult to split?

On Tue, 22 Aug 2006 06:47:13 GMT, "BJ"
wrote:

OK, but what about Freeview and cable............a Freeview PVR only has one
aerial input but can have 2 tuners and perform the same functions as a sky+
box. A Telewest "TV Drive" Cable PVR only has one co-ax input but has
multiple tuners and performs the same functions as a Sky+ box.

Some Freeview PVR's do. The Topfield 5800 has two inputs, one for each
tuner, that are daisy chained from the main aerial feed.
--
Andrew, contact via http://interpleb.googlepages.com
Help make Usenet a better place: English is read downwards,
please don't top post. Trim replies to quote only relevant text.
Check groups.google.com before asking an obvious question.

"Andrew" wrote in message
...
Some Freeview PVR's do. The Topfield 5800 has two inputs, one for each
tuner, that are daisy chained from the main aerial feed.
--
But that is my question, you can't daisychain one sky feed to the 2 inputs
on a sky+ box, you can't even split the signal with those sat signal
splitters that they sell in Maplins. It has to be 2 distinct feeds from the
dish. Why?

"BJ" wrote in message
.uk...
Well, why does Sky+ need 2 co-ax inputs from the dish?

The answer would be: "It has 2 tuners, mate" or "think of it as 2 boxes,
pal" or "you would need 2 feeds to 2 rooms with 2 people watching
different channels, sky+ is the same, mate".

OK, but what about Freeview and cable............a Freeview PVR only has
one aerial input but can have 2 tuners and perform the same functions as a
sky+ box. A Telewest "TV Drive" Cable PVR only has one co-ax input but has
multiple tuners and performs the same functions as a Sky+ box.

Why can the Sky+ box not work quite happily with one feed from the dish?
Was the Sky+ box designed so that it requires 2 feeds. Could it have been
designed like the Telewest box so that it only needs one
feed................or is it something to do with the frequency of the sat
signal, making it difficult to split?

I believe it is to do with the fact that the original satellite dish LNB's
switched between horizontal and vertical polarity by switching a DC voltage
along the cable to the dish. Since with Sky+ you could be watching a
channel on H polarity while recording something on V polarity, this can't be
done with one cable or LNB. Therefore, the Sky+ requires a twin LNB with
two cables.

Well, the cable into the box isn't just a straightforward feed. It
also carries the high/low and polarisation switching signals back to
the LNB. Clearly these could be different for 2 different channels.
Hence the need for a quad LNB as well.
Make sense?


BJ wrote:
Well, why does Sky+ need 2 co-ax inputs from the dish?

and Buffalo has put it more eloquently than me. (Must type faster,
lol).

wrote:
Well, the cable into the box isn't just a straightforward feed. It
also carries the high/low and polarisation switching signals back to
the LNB. Clearly these could be different for 2 different channels.
Hence the need for a quad LNB as well.
Make sense?


BJ wrote:
Well, why does Sky+ need 2 co-ax inputs from the dish?

wrote in message
ps.com...
and Buffalo has put it more eloquently than me. (Must type faster,
lol).

Thanks to you both for your replies

BJ wrote:
Well, why does Sky+ need 2 co-ax inputs from the dish?

The answer would be: "It has 2 tuners, mate" or "think of it as 2
boxes, pal" or "you would need 2 feeds to 2 rooms with 2 people
watching different channels, sky+ is the same, mate".

OK, but what about Freeview and cable............a Freeview PVR only
has one aerial input but can have 2 tuners and perform the same
functions as a sky+ box. A Telewest "TV Drive" Cable PVR only has one
co-ax input but has multiple tuners and performs the same functions
as a Sky+ box.
.
Why can the Sky+ box not work quite happily with one feed from the
dish? Was the Sky+ box designed so that it requires 2 feeds. Could it
have been designed like the Telewest box so that it only needs one
feed................or is it something to do with the frequency of
the sat signal, making it difficult to split?

Satellite signals can be horizontal or vertical, high or low band. If you
wanted for example to record one high band channel and one low, then you
would need two feeds. If both were say high, then you could daisy chain.
--
Adrian

BJ wrote:
Why can the Sky+ box not work quite happily with one feed from the dish? Was
the Sky+ box designed so that it requires 2 feeds. Could it have been
designed like the Telewest box so that it only needs one
feed................or is it something to do with the frequency of the sat
signal, making it difficult to split?

Short explanation; there might only be one thing stuck on the front of
the dish but it actually has four modes it can be in to pick up four
different kinds of signal, with the digibox telling it which mode to be in.

If it's in one mode it physically can't receive the signals sent in the
other three modes. If the channel that one tuner is looking at is in
transmitted in one mode and the channel that the other tuner wants to
look at is transmitted in another mode then it's not physically possible
for it to pick up that signal. It needs to change mode - but if it does
that it will stop receiving the first signal.

The Sky+ could quite happily work with one feed split to both inputs,
but it would only be able to use both tuners if the channels required
were in the same signal mode - i.e. about 1/4 of the time.

--
Angus G Rae Science & Engineering Support Team
Computing Services
University of Edinburgh
The above opinions are mine, and Edinburgh University can't have them

"Angus Rae" wrote in message
...
BJ wrote:
Why can the Sky+ box not work quite happily with one feed from the dish?
Was the Sky+ box designed so that it requires 2 feeds. Could it have been
designed like the Telewest box so that it only needs one
feed................or is it something to do with the frequency of the
sat signal, making it difficult to split?

Short explanation; there might only be one thing stuck on the front of the
dish but it actually has four modes it can be in to pick up four different
kinds of signal, with the digibox telling it which mode to be in.

If it's in one mode it physically can't receive the signals sent in the
other three modes. If the channel that one tuner is looking at is in
transmitted in one mode and the channel that the other tuner wants to look
at is transmitted in another mode then it's not physically possible for it
to pick up that signal. It needs to change mode - but if it does that it
will stop receiving the first signal.

The Sky+ could quite happily work with one feed split to both inputs, but
it would only be able to use both tuners if the channels required were in
the same signal mode - i.e. about 1/4 of the time.

--
Angus G Rae Science & Engineering Support Team
Computing Services
University of Edinburgh
The above opinions are mine, and Edinburgh University can't have them

Thanks for the replies. I think/hope that I understand the answers. But
there is one thing that bothers me. If I got one of those sat signal
splitters from Maplins, according to the Maplin website I would be able to
have 2 standard sky boxes off one feed (the Maplin website makes it clear
that this splitter is not suitable for Sky+).
I could then stack the boxes on top of each other and have one feed the
telly/VCR and one feed a DVD recorder (all off one cable). I could watch one
channel whilst recording another channel. I could even record 2 different
channels at once (VCR and DVD/Hard drive). I would even be able to timeslip
live TV if I bought a DVD recorder with this facility. I would have all the
facilities of Sky+ with the ability to archive to DVD or tape thrown in. I
also wouldn't have the cost of additional installation (for the extra feed)
and ongoing subscription.

Does the sky+ box have separate decoders for each tuner? Why does the
hardware behave differently from 2 separate boxes? Apologies in advance if
all this is very dumb but I just wish to pursue the uniqueness of Sky+ a
little further.