Don Bishop writes:
>I finally found a description of the repeater.  Does anyone happen to know how
> the thing works?  Sounds like it picks up the xm signals and retransmits
>them,
>but on what frequencies?  And, how does the xm radio know to tune into the rep
>eater rather than the terestrial signal directly?

        It doesn't have to know.  They are one in the same.  The XM
and Serius services are in the K U band which is around 11 or 12
gigahertz.  That's way up there, all right.  The neat thing about
those frequencies is that you can have a repeater  whose transmit and
receive frequencies are the same.  The trick is that the output can
not be in line of sight of the input so the repeater is kind of like
an amplified pipe.  You put the receive antenna where it picks up the
best signal from the satellite and then aim the transmitting antenna
in to your cave or under your favorite rock where the satellite signal
doesn't go.

        I would imagine that there are certain configurations that
will kill the repeater if the signal reflects from the output back in
to the input, but normally, they won't see each other at all.

        Brodcast engineers do this in the 2.5 GHZ range to relay
domestic television feeds from remote sites back to the studio such as
when a mobile television truck initiates a broadcast from your local
shopping center and wants to send it back to the station but can't get
a clear path.  They may have a repeater truck set up somewhere in site
of both points and relay the signal.

Martin McCormick WB5AGZ  Stillwater, OK
OSU Information Technology Department Network Operations Group