Alexandre, I've been with DirecTV for a few years. The LNAs switch
between left and right circular polarization for odd and even
transponders. The receiver provides the control voltage. The newer
"Plus" systems that can receive satellites in another orbital `slot'
using an eliptical dish, also add a tone activated switch to select LNAs.
The Dish network is the same as far as polarization switching. A typical
complaint is only receiving channels on odd or even transponders which
indicates a bad LNA, the cable from the receiver to the LNA, or the
receiver control voltage.

   - Tom

At 17:20 25-12-01 -0200, Alexandre Domingos F. Souza wrote:
>>A DBS box splitter contains a few diodes that prevent the various boxes
>>from each feeding the downconverter supply (only one does). There are
>>usually instructions on which port has control. The other port is limited
>>to see channels with the same polarization (as selected by the first box).
>
>        Nice question! In Directv and Sky systems, you change the
polarization in the LNB? I though there was only one polarization, or
circular polarization. How does the IRD changes that? Changing the voltage
feed to the LNB?


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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