Re: TV Distro

[Jim Noble <yahoo-groups@xxxxxxxxxxxxxxxxxx>]

On 15 Apr 2008, at 20:39, Rob Mouser wrote:
> This simply amplifies the signal from the LNB allowing you to run
> multiple boxes?

There's more going on than that. The LNB on your dish can produce 4
possible signals; Vertical or Horizontal polarisation, combined with
high or low band. The satellite channels are spread over the 4
combinations of polarity and band, so when you tune to a particular
channel on your receiver, it has to tell LNB which of the 4 signals
that channel can be found in.

To do this, the satellite receiver sends a signal up the coax to the
LNB to select one of the 4 combinations of polarisation and band. You
can't connect more than one tuner to the LNB output as the control
signals would clash, so you need one LNB output per tuner (thus sky+/
hd boxes need two feeds).

However, if you have a quad LNB you have enough outputs to select all
of the possible signals simultaneously. A multi-switch statically
selects all 4 signals from a quad or quattro LNB, amplifies them, and
feeds one of the 4 signals to each of many (>4) outputs according to
the signal sent up the coax by each receiver.

(Some of them have a feed-through outputs from the LNB so that you can
chain them together and thus connect a large number of receivers to a
single dish. This is often used in eg blocks of flats so you don't end
up with a sea of satellite dishes all over one wall).

Jim

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